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diff --git a/documentation/dev-manual/common-tasks.rst b/documentation/dev-manual/common-tasks.rst new file mode 100644 index 0000000000..c627491f39 --- /dev/null +++ b/documentation/dev-manual/common-tasks.rst @@ -0,0 +1,11582 @@ +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK + +************ +Common Tasks +************ + +This chapter describes fundamental procedures such as creating layers, +adding new software packages, extending or customizing images, porting +work to new hardware (adding a new machine), and so forth. You will find +that the procedures documented here occur often in the development cycle +using the Yocto Project. + +Understanding and Creating Layers +================================= + +The OpenEmbedded build system supports organizing +:term:`Metadata` into multiple layers. +Layers allow you to isolate different types of customizations from each +other. For introductory information on the Yocto Project Layer Model, +see the +":ref:`overview-manual/overview-manual-yp-intro:the yocto project layer model`" +section in the Yocto Project Overview and Concepts Manual. + +Creating Your Own Layer +----------------------- + +It is very easy to create your own layers to use with the OpenEmbedded +build system. The Yocto Project ships with tools that speed up creating +layers. This section describes the steps you perform by hand to create +layers so that you can better understand them. For information about the +layer-creation tools, see the +":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`" +section in the Yocto Project Board Support Package (BSP) Developer's +Guide and the ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`" +section further down in this manual. + +Follow these general steps to create your layer without using tools: + +1. *Check Existing Layers:* Before creating a new layer, you should be + sure someone has not already created a layer containing the Metadata + you need. You can see the `OpenEmbedded Metadata + Index <https://layers.openembedded.org/layerindex/layers/>`__ for a + list of layers from the OpenEmbedded community that can be used in + the Yocto Project. You could find a layer that is identical or close + to what you need. + +2. *Create a Directory:* Create the directory for your layer. When you + create the layer, be sure to create the directory in an area not + associated with the Yocto Project :term:`Source Directory` + (e.g. the cloned ``poky`` repository). + + While not strictly required, prepend the name of the directory with + the string "meta-". For example: + :: + + meta-mylayer + meta-GUI_xyz + meta-mymachine + + With rare exceptions, a layer's name follows this form: + :: + + meta-root_name + + Following this layer naming convention can save + you trouble later when tools, components, or variables "assume" your + layer name begins with "meta-". A notable example is in configuration + files as shown in the following step where layer names without the + "meta-" string are appended to several variables used in the + configuration. + +3. *Create a Layer Configuration File:* Inside your new layer folder, + you need to create a ``conf/layer.conf`` file. It is easiest to take + an existing layer configuration file and copy that to your layer's + ``conf`` directory and then modify the file as needed. + + The ``meta-yocto-bsp/conf/layer.conf`` file in the Yocto Project + :yocto_git:`Source Repositories </poky/tree/meta-yocto-bsp/conf>` + demonstrates the required syntax. For your layer, you need to replace + "yoctobsp" with a unique identifier for your layer (e.g. "machinexyz" + for a layer named "meta-machinexyz"): + :: + + # We have a conf and classes directory, add to BBPATH + BBPATH .= ":${LAYERDIR}" + + # We have recipes-* directories, add to BBFILES + BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \ + ${LAYERDIR}/recipes-*/*/*.bbappend" + + BBFILE_COLLECTIONS += "yoctobsp" + BBFILE_PATTERN_yoctobsp = "^${LAYERDIR}/" + BBFILE_PRIORITY_yoctobsp = "5" + LAYERVERSION_yoctobsp = "4" + LAYERSERIES_COMPAT_yoctobsp = "dunfell" + + Following is an explanation of the layer configuration file: + + - :term:`BBPATH`: Adds the layer's + root directory to BitBake's search path. Through the use of the + ``BBPATH`` variable, BitBake locates class files (``.bbclass``), + configuration files, and files that are included with ``include`` + and ``require`` statements. For these cases, BitBake uses the + first file that matches the name found in ``BBPATH``. This is + similar to the way the ``PATH`` variable is used for binaries. It + is recommended, therefore, that you use unique class and + configuration filenames in your custom layer. + + - :term:`BBFILES`: Defines the + location for all recipes in the layer. + + - :term:`BBFILE_COLLECTIONS`: + Establishes the current layer through a unique identifier that is + used throughout the OpenEmbedded build system to refer to the + layer. In this example, the identifier "yoctobsp" is the + representation for the container layer named "meta-yocto-bsp". + + - :term:`BBFILE_PATTERN`: + Expands immediately during parsing to provide the directory of the + layer. + + - :term:`BBFILE_PRIORITY`: + Establishes a priority to use for recipes in the layer when the + OpenEmbedded build finds recipes of the same name in different + layers. + + - :term:`LAYERVERSION`: + Establishes a version number for the layer. You can use this + version number to specify this exact version of the layer as a + dependency when using the + :term:`LAYERDEPENDS` + variable. + + - :term:`LAYERDEPENDS`: + Lists all layers on which this layer depends (if any). + + - :term:`LAYERSERIES_COMPAT`: + Lists the :yocto_wiki:`Yocto Project </Releases>` + releases for which the current version is compatible. This + variable is a good way to indicate if your particular layer is + current. + +4. *Add Content:* Depending on the type of layer, add the content. If + the layer adds support for a machine, add the machine configuration + in a ``conf/machine/`` file within the layer. If the layer adds + distro policy, add the distro configuration in a ``conf/distro/`` + file within the layer. If the layer introduces new recipes, put the + recipes you need in ``recipes-*`` subdirectories within the layer. + + .. note:: + + For an explanation of layer hierarchy that is compliant with the + Yocto Project, see the ":ref:`bsp-guide/bsp:example filesystem layout`" + section in the Yocto Project Board Support Package (BSP) Developer's Guide. + +5. *Optionally Test for Compatibility:* If you want permission to use + the Yocto Project Compatibility logo with your layer or application + that uses your layer, perform the steps to apply for compatibility. + See the "`Making Sure Your Layer is Compatible With Yocto + Project <#making-sure-your-layer-is-compatible-with-yocto-project>`__" + section for more information. + +Following Best Practices When Creating Layers +--------------------------------------------- + +To create layers that are easier to maintain and that will not impact +builds for other machines, you should consider the information in the +following list: + +- *Avoid "Overlaying" Entire Recipes from Other Layers in Your + Configuration:* In other words, do not copy an entire recipe into + your layer and then modify it. Rather, use an append file + (``.bbappend``) to override only those parts of the original recipe + you need to modify. + +- *Avoid Duplicating Include Files:* Use append files (``.bbappend``) + for each recipe that uses an include file. Or, if you are introducing + a new recipe that requires the included file, use the path relative + to the original layer directory to refer to the file. For example, + use ``require recipes-core/``\ `package`\ ``/``\ `file`\ ``.inc`` instead + of ``require`` `file`\ ``.inc``. If you're finding you have to overlay + the include file, it could indicate a deficiency in the include file + in the layer to which it originally belongs. If this is the case, you + should try to address that deficiency instead of overlaying the + include file. For example, you could address this by getting the + maintainer of the include file to add a variable or variables to make + it easy to override the parts needing to be overridden. + +- *Structure Your Layers:* Proper use of overrides within append files + and placement of machine-specific files within your layer can ensure + that a build is not using the wrong Metadata and negatively impacting + a build for a different machine. Following are some examples: + + - *Modify Variables to Support a Different Machine:* Suppose you + have a layer named ``meta-one`` that adds support for building + machine "one". To do so, you use an append file named + ``base-files.bbappend`` and create a dependency on "foo" by + altering the :term:`DEPENDS` + variable: + :: + + DEPENDS = "foo" + + The dependency is created during any + build that includes the layer ``meta-one``. However, you might not + want this dependency for all machines. For example, suppose you + are building for machine "two" but your ``bblayers.conf`` file has + the ``meta-one`` layer included. During the build, the + ``base-files`` for machine "two" will also have the dependency on + ``foo``. + + To make sure your changes apply only when building machine "one", + use a machine override with the ``DEPENDS`` statement: + :: + + DEPENDS_one = "foo" + + You should follow the same strategy when using ``_append`` + and ``_prepend`` operations: + :: + + DEPENDS_append_one = " foo" + DEPENDS_prepend_one = "foo " + + As an actual example, here's a + snippet from the generic kernel include file ``linux-yocto.inc``, + wherein the kernel compile and link options are adjusted in the + case of a subset of the supported architectures: + :: + + DEPENDS_append_aarch64 = " libgcc" + KERNEL_CC_append_aarch64 = " ${TOOLCHAIN_OPTIONS}" + KERNEL_LD_append_aarch64 = " ${TOOLCHAIN_OPTIONS}" + + DEPENDS_append_nios2 = " libgcc" + KERNEL_CC_append_nios2 = " ${TOOLCHAIN_OPTIONS}" + KERNEL_LD_append_nios2 = " ${TOOLCHAIN_OPTIONS}" + + DEPENDS_append_arc = " libgcc" + KERNEL_CC_append_arc = " ${TOOLCHAIN_OPTIONS}" + KERNEL_LD_append_arc = " ${TOOLCHAIN_OPTIONS}" + + KERNEL_FEATURES_append_qemuall=" features/debug/printk.scc" + + .. note:: + + Avoiding "+=" and "=+" and using machine-specific ``_append`` + and ``_prepend`` operations is recommended as well. + + - *Place Machine-Specific Files in Machine-Specific Locations:* When + you have a base recipe, such as ``base-files.bb``, that contains a + :term:`SRC_URI` statement to a + file, you can use an append file to cause the build to use your + own version of the file. For example, an append file in your layer + at ``meta-one/recipes-core/base-files/base-files.bbappend`` could + extend :term:`FILESPATH` using :term:`FILESEXTRAPATHS` as follows: + :: + + FILESEXTRAPATHS_prepend := "${THISDIR}/${BPN}:" + + The build for machine "one" will pick up your machine-specific file as + long as you have the file in + ``meta-one/recipes-core/base-files/base-files/``. However, if you + are building for a different machine and the ``bblayers.conf`` + file includes the ``meta-one`` layer and the location of your + machine-specific file is the first location where that file is + found according to ``FILESPATH``, builds for all machines will + also use that machine-specific file. + + You can make sure that a machine-specific file is used for a + particular machine by putting the file in a subdirectory specific + to the machine. For example, rather than placing the file in + ``meta-one/recipes-core/base-files/base-files/`` as shown above, + put it in ``meta-one/recipes-core/base-files/base-files/one/``. + Not only does this make sure the file is used only when building + for machine "one", but the build process locates the file more + quickly. + + In summary, you need to place all files referenced from + ``SRC_URI`` in a machine-specific subdirectory within the layer in + order to restrict those files to machine-specific builds. + +- *Perform Steps to Apply for Yocto Project Compatibility:* If you want + permission to use the Yocto Project Compatibility logo with your + layer or application that uses your layer, perform the steps to apply + for compatibility. See the "`Making Sure Your Layer is Compatible + With Yocto + Project <#making-sure-your-layer-is-compatible-with-yocto-project>`__" + section for more information. + +- *Follow the Layer Naming Convention:* Store custom layers in a Git + repository that use the ``meta-layer_name`` format. + +- *Group Your Layers Locally:* Clone your repository alongside other + cloned ``meta`` directories from the :term:`Source Directory`. + +Making Sure Your Layer is Compatible With Yocto Project +------------------------------------------------------- + +When you create a layer used with the Yocto Project, it is advantageous +to make sure that the layer interacts well with existing Yocto Project +layers (i.e. the layer is compatible with the Yocto Project). Ensuring +compatibility makes the layer easy to be consumed by others in the Yocto +Project community and could allow you permission to use the Yocto +Project Compatible Logo. + +.. note:: + + Only Yocto Project member organizations are permitted to use the + Yocto Project Compatible Logo. The logo is not available for general + use. For information on how to become a Yocto Project member + organization, see the :yocto_home:`Yocto Project Website <>`. + +The Yocto Project Compatibility Program consists of a layer application +process that requests permission to use the Yocto Project Compatibility +Logo for your layer and application. The process consists of two parts: + +1. Successfully passing a script (``yocto-check-layer``) that when run + against your layer, tests it against constraints based on experiences + of how layers have worked in the real world and where pitfalls have + been found. Getting a "PASS" result from the script is required for + successful compatibility registration. + +2. Completion of an application acceptance form, which you can find at + https://www.yoctoproject.org/webform/yocto-project-compatible-registration. + +To be granted permission to use the logo, you need to satisfy the +following: + +- Be able to check the box indicating that you got a "PASS" when + running the script against your layer. + +- Answer "Yes" to the questions on the form or have an acceptable + explanation for any questions answered "No". + +- Be a Yocto Project Member Organization. + +The remainder of this section presents information on the registration +form and on the ``yocto-check-layer`` script. + +Yocto Project Compatible Program Application +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Use the form to apply for your layer's approval. Upon successful +application, you can use the Yocto Project Compatibility Logo with your +layer and the application that uses your layer. + +To access the form, use this link: +https://www.yoctoproject.org/webform/yocto-project-compatible-registration. +Follow the instructions on the form to complete your application. + +The application consists of the following sections: + +- *Contact Information:* Provide your contact information as the fields + require. Along with your information, provide the released versions + of the Yocto Project for which your layer is compatible. + +- *Acceptance Criteria:* Provide "Yes" or "No" answers for each of the + items in the checklist. Space exists at the bottom of the form for + any explanations for items for which you answered "No". + +- *Recommendations:* Provide answers for the questions regarding Linux + kernel use and build success. + +``yocto-check-layer`` Script +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``yocto-check-layer`` script provides you a way to assess how +compatible your layer is with the Yocto Project. You should run this +script prior to using the form to apply for compatibility as described +in the previous section. You need to achieve a "PASS" result in order to +have your application form successfully processed. + +The script divides tests into three areas: COMMON, BSP, and DISTRO. For +example, given a distribution layer (DISTRO), the layer must pass both +the COMMON and DISTRO related tests. Furthermore, if your layer is a BSP +layer, the layer must pass the COMMON and BSP set of tests. + +To execute the script, enter the following commands from your build +directory: +:: + + $ source oe-init-build-env + $ yocto-check-layer your_layer_directory + +Be sure to provide the actual directory for your +layer as part of the command. + +Entering the command causes the script to determine the type of layer +and then to execute a set of specific tests against the layer. The +following list overviews the test: + +- ``common.test_readme``: Tests if a ``README`` file exists in the + layer and the file is not empty. + +- ``common.test_parse``: Tests to make sure that BitBake can parse the + files without error (i.e. ``bitbake -p``). + +- ``common.test_show_environment``: Tests that the global or per-recipe + environment is in order without errors (i.e. ``bitbake -e``). + +- ``common.test_world``: Verifies that ``bitbake world`` works. + +- ``common.test_signatures``: Tests to be sure that BSP and DISTRO + layers do not come with recipes that change signatures. + +- ``common.test_layerseries_compat``: Verifies layer compatibility is + set properly. + +- ``bsp.test_bsp_defines_machines``: Tests if a BSP layer has machine + configurations. + +- ``bsp.test_bsp_no_set_machine``: Tests to ensure a BSP layer does not + set the machine when the layer is added. + +- ``bsp.test_machine_world``: Verifies that ``bitbake world`` works + regardless of which machine is selected. + +- ``bsp.test_machine_signatures``: Verifies that building for a + particular machine affects only the signature of tasks specific to + that machine. + +- ``distro.test_distro_defines_distros``: Tests if a DISTRO layer has + distro configurations. + +- ``distro.test_distro_no_set_distros``: Tests to ensure a DISTRO layer + does not set the distribution when the layer is added. + +Enabling Your Layer +------------------- + +Before the OpenEmbedded build system can use your new layer, you need to +enable it. To enable your layer, simply add your layer's path to the +``BBLAYERS`` variable in your ``conf/bblayers.conf`` file, which is +found in the :term:`Build Directory`. +The following example shows how to enable a layer named +``meta-mylayer``: +:: + + # POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf + # changes incompatibly + POKY_BBLAYERS_CONF_VERSION = "2" + BBPATH = "${TOPDIR}" + BBFILES ?= "" + BBLAYERS ?= " \ + /home/user/poky/meta \ + /home/user/poky/meta-poky \ + /home/user/poky/meta-yocto-bsp \ + /home/user/poky/meta-mylayer \ + " + +BitBake parses each ``conf/layer.conf`` file from the top down as +specified in the ``BBLAYERS`` variable within the ``conf/bblayers.conf`` +file. During the processing of each ``conf/layer.conf`` file, BitBake +adds the recipes, classes and configurations contained within the +particular layer to the source directory. + +Using .bbappend Files in Your Layer +----------------------------------- + +A recipe that appends Metadata to another recipe is called a BitBake +append file. A BitBake append file uses the ``.bbappend`` file type +suffix, while the corresponding recipe to which Metadata is being +appended uses the ``.bb`` file type suffix. + +You can use a ``.bbappend`` file in your layer to make additions or +changes to the content of another layer's recipe without having to copy +the other layer's recipe into your layer. Your ``.bbappend`` file +resides in your layer, while the main ``.bb`` recipe file to which you +are appending Metadata resides in a different layer. + +Being able to append information to an existing recipe not only avoids +duplication, but also automatically applies recipe changes from a +different layer into your layer. If you were copying recipes, you would +have to manually merge changes as they occur. + +When you create an append file, you must use the same root name as the +corresponding recipe file. For example, the append file +``someapp_3.1.bbappend`` must apply to ``someapp_3.1.bb``. This +means the original recipe and append file names are version +number-specific. If the corresponding recipe is renamed to update to a +newer version, you must also rename and possibly update the +corresponding ``.bbappend`` as well. During the build process, BitBake +displays an error on starting if it detects a ``.bbappend`` file that +does not have a corresponding recipe with a matching name. See the +:term:`BB_DANGLINGAPPENDS_WARNONLY` +variable for information on how to handle this error. + +As an example, consider the main formfactor recipe and a corresponding +formfactor append file both from the :term:`Source Directory`. +Here is the main +formfactor recipe, which is named ``formfactor_0.0.bb`` and located in +the "meta" layer at ``meta/recipes-bsp/formfactor``: +:: + + SUMMARY = "Device formfactor information" + DESCRIPTION = "A formfactor configuration file provides information about the \ + target hardware for which the image is being built and information that the \ + build system cannot obtain from other sources such as the kernel." + SECTION = "base" + LICENSE = "MIT" + LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420" + PR = "r45" + + SRC_URI = "file://config file://machconfig" + S = "${WORKDIR}" + + PACKAGE_ARCH = "${MACHINE_ARCH}" + INHIBIT_DEFAULT_DEPS = "1" + + do_install() { + # Install file only if it has contents + install -d ${D}${sysconfdir}/formfactor/ + install -m 0644 ${S}/config ${D}${sysconfdir}/formfactor/ + if [ -s "${S}/machconfig" ]; then + install -m 0644 ${S}/machconfig ${D}${sysconfdir}/formfactor/ + fi + } + +In the main recipe, note the :term:`SRC_URI` +variable, which tells the OpenEmbedded build system where to find files +during the build. + +Following is the append file, which is named ``formfactor_0.0.bbappend`` +and is from the Raspberry Pi BSP Layer named ``meta-raspberrypi``. The +file is in the layer at ``recipes-bsp/formfactor``: +:: + + FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + +By default, the build system uses the +:term:`FILESPATH` variable to +locate files. This append file extends the locations by setting the +:term:`FILESEXTRAPATHS` +variable. Setting this variable in the ``.bbappend`` file is the most +reliable and recommended method for adding directories to the search +path used by the build system to find files. + +The statement in this example extends the directories to include +``${``\ :term:`THISDIR`\ ``}/${``\ :term:`PN`\ ``}``, +which resolves to a directory named ``formfactor`` in the same directory +in which the append file resides (i.e. +``meta-raspberrypi/recipes-bsp/formfactor``. This implies that you must +have the supporting directory structure set up that will contain any +files or patches you will be including from the layer. + +Using the immediate expansion assignment operator ``:=`` is important +because of the reference to ``THISDIR``. The trailing colon character is +important as it ensures that items in the list remain colon-separated. + +.. note:: + + BitBake automatically defines the ``THISDIR`` variable. You should + never set this variable yourself. Using "_prepend" as part of the + ``FILESEXTRAPATHS`` ensures your path will be searched prior to other + paths in the final list. + + Also, not all append files add extra files. Many append files simply + exist to add build options (e.g. ``systemd``). For these cases, your + append file would not even use the ``FILESEXTRAPATHS`` statement. + +Prioritizing Your Layer +----------------------- + +Each layer is assigned a priority value. Priority values control which +layer takes precedence if there are recipe files with the same name in +multiple layers. For these cases, the recipe file from the layer with a +higher priority number takes precedence. Priority values also affect the +order in which multiple ``.bbappend`` files for the same recipe are +applied. You can either specify the priority manually, or allow the +build system to calculate it based on the layer's dependencies. + +To specify the layer's priority manually, use the +:term:`BBFILE_PRIORITY` +variable and append the layer's root name: +:: + + BBFILE_PRIORITY_mylayer = "1" + +.. note:: + + It is possible for a recipe with a lower version number + :term:`PV` in a layer that has a higher + priority to take precedence. + + Also, the layer priority does not currently affect the precedence + order of ``.conf`` or ``.bbclass`` files. Future versions of BitBake + might address this. + +Managing Layers +--------------- + +You can use the BitBake layer management tool ``bitbake-layers`` to +provide a view into the structure of recipes across a multi-layer +project. Being able to generate output that reports on configured layers +with their paths and priorities and on ``.bbappend`` files and their +applicable recipes can help to reveal potential problems. + +For help on the BitBake layer management tool, use the following +command: +:: + + $ bitbake-layers --help + NOTE: Starting bitbake server... + usage: bitbake-layers [-d] [-q] [-F] [--color COLOR] [-h] <subcommand> ... + + BitBake layers utility + + optional arguments: + -d, --debug Enable debug output + -q, --quiet Print only errors + -F, --force Force add without recipe parse verification + --color COLOR Colorize output (where COLOR is auto, always, never) + -h, --help show this help message and exit + + subcommands: + <subcommand> + layerindex-fetch Fetches a layer from a layer index along with its + dependent layers, and adds them to conf/bblayers.conf. + layerindex-show-depends + Find layer dependencies from layer index. + add-layer Add one or more layers to bblayers.conf. + remove-layer Remove one or more layers from bblayers.conf. + flatten flatten layer configuration into a separate output + directory. + show-layers show current configured layers. + show-overlayed list overlayed recipes (where the same recipe exists + in another layer) + show-recipes list available recipes, showing the layer they are + provided by + show-appends list bbappend files and recipe files they apply to + show-cross-depends Show dependencies between recipes that cross layer + boundaries. + create-layer Create a basic layer + + Use bitbake-layers <subcommand> --help to get help on a specific command + +The following list describes the available commands: + +- ``help:`` Displays general help or help on a specified command. + +- ``show-layers:`` Shows the current configured layers. + +- ``show-overlayed:`` Lists overlayed recipes. A recipe is overlayed + when a recipe with the same name exists in another layer that has a + higher layer priority. + +- ``show-recipes:`` Lists available recipes and the layers that + provide them. + +- ``show-appends:`` Lists ``.bbappend`` files and the recipe files to + which they apply. + +- ``show-cross-depends:`` Lists dependency relationships between + recipes that cross layer boundaries. + +- ``add-layer:`` Adds a layer to ``bblayers.conf``. + +- ``remove-layer:`` Removes a layer from ``bblayers.conf`` + +- ``flatten:`` Flattens the layer configuration into a separate + output directory. Flattening your layer configuration builds a + "flattened" directory that contains the contents of all layers, with + any overlayed recipes removed and any ``.bbappend`` files appended to + the corresponding recipes. You might have to perform some manual + cleanup of the flattened layer as follows: + + - Non-recipe files (such as patches) are overwritten. The flatten + command shows a warning for these files. + + - Anything beyond the normal layer setup has been added to the + ``layer.conf`` file. Only the lowest priority layer's + ``layer.conf`` is used. + + - Overridden and appended items from ``.bbappend`` files need to be + cleaned up. The contents of each ``.bbappend`` end up in the + flattened recipe. However, if there are appended or changed + variable values, you need to tidy these up yourself. Consider the + following example. Here, the ``bitbake-layers`` command adds the + line ``#### bbappended ...`` so that you know where the following + lines originate: + :: + + ... + DESCRIPTION = "A useful utility" + ... + EXTRA_OECONF = "--enable-something" + ... + + #### bbappended from meta-anotherlayer #### + + DESCRIPTION = "Customized utility" + EXTRA_OECONF += "--enable-somethingelse" + + + Ideally, you would tidy up these utilities as follows: + :: + + ... + DESCRIPTION = "Customized utility" + ... + EXTRA_OECONF = "--enable-something --enable-somethingelse" + ... + +- ``layerindex-fetch``: Fetches a layer from a layer index, along + with its dependent layers, and adds the layers to the + ``conf/bblayers.conf`` file. + +- ``layerindex-show-depends``: Finds layer dependencies from the + layer index. + +- ``create-layer``: Creates a basic layer. + +Creating a General Layer Using the ``bitbake-layers`` Script +------------------------------------------------------------ + +The ``bitbake-layers`` script with the ``create-layer`` subcommand +simplifies creating a new general layer. + +.. note:: + + - For information on BSP layers, see the ":ref:`bsp-guide/bsp:bsp layers`" + section in the Yocto + Project Board Specific (BSP) Developer's Guide. + + - In order to use a layer with the OpenEmbedded build system, you + need to add the layer to your ``bblayers.conf`` configuration + file. See the ":ref:`dev-manual/common-tasks:adding a layer using the \`\`bitbake-layers\`\` script`" + section for more information. + +The default mode of the script's operation with this subcommand is to +create a layer with the following: + +- A layer priority of 6. + +- A ``conf`` subdirectory that contains a ``layer.conf`` file. + +- A ``recipes-example`` subdirectory that contains a further + subdirectory named ``example``, which contains an ``example.bb`` + recipe file. + +- A ``COPYING.MIT``, which is the license statement for the layer. The + script assumes you want to use the MIT license, which is typical for + most layers, for the contents of the layer itself. + +- A ``README`` file, which is a file describing the contents of your + new layer. + +In its simplest form, you can use the following command form to create a +layer. The command creates a layer whose name corresponds to +"your_layer_name" in the current directory: +:: + + $ bitbake-layers create-layer your_layer_name + +As an example, the following command creates a layer named ``meta-scottrif`` +in your home directory: +:: + + $ cd /usr/home + $ bitbake-layers create-layer meta-scottrif + NOTE: Starting bitbake server... + Add your new layer with 'bitbake-layers add-layer meta-scottrif' + +If you want to set the priority of the layer to other than the default +value of "6", you can either use the ``--priority`` option or you +can edit the +:term:`BBFILE_PRIORITY` value +in the ``conf/layer.conf`` after the script creates it. Furthermore, if +you want to give the example recipe file some name other than the +default, you can use the ``--example-recipe-name`` option. + +The easiest way to see how the ``bitbake-layers create-layer`` command +works is to experiment with the script. You can also read the usage +information by entering the following: +:: + + $ bitbake-layers create-layer --help + NOTE: Starting bitbake server... + usage: bitbake-layers create-layer [-h] [--priority PRIORITY] + [--example-recipe-name EXAMPLERECIPE] + layerdir + + Create a basic layer + + positional arguments: + layerdir Layer directory to create + + optional arguments: + -h, --help show this help message and exit + --priority PRIORITY, -p PRIORITY + Layer directory to create + --example-recipe-name EXAMPLERECIPE, -e EXAMPLERECIPE + Filename of the example recipe + +Adding a Layer Using the ``bitbake-layers`` Script +-------------------------------------------------- + +Once you create your general layer, you must add it to your +``bblayers.conf`` file. Adding the layer to this configuration file +makes the OpenEmbedded build system aware of your layer so that it can +search it for metadata. + +Add your layer by using the ``bitbake-layers add-layer`` command: +:: + + $ bitbake-layers add-layer your_layer_name + +Here is an example that adds a +layer named ``meta-scottrif`` to the configuration file. Following the +command that adds the layer is another ``bitbake-layers`` command that +shows the layers that are in your ``bblayers.conf`` file: +:: + + $ bitbake-layers add-layer meta-scottrif + NOTE: Starting bitbake server... + Parsing recipes: 100% |##########################################################| Time: 0:00:49 + Parsing of 1441 .bb files complete (0 cached, 1441 parsed). 2055 targets, 56 skipped, 0 masked, 0 errors. + $ bitbake-layers show-layers + NOTE: Starting bitbake server... + layer path priority + ========================================================================== + meta /home/scottrif/poky/meta 5 + meta-poky /home/scottrif/poky/meta-poky 5 + meta-yocto-bsp /home/scottrif/poky/meta-yocto-bsp 5 + workspace /home/scottrif/poky/build/workspace 99 + meta-scottrif /home/scottrif/poky/build/meta-scottrif 6 + + +Adding the layer to this file +enables the build system to locate the layer during the build. + +.. note:: + + During a build, the OpenEmbedded build system looks in the layers + from the top of the list down to the bottom in that order. + +Customizing Images +================== + +You can customize images to satisfy particular requirements. This +section describes several methods and provides guidelines for each. + +Customizing Images Using ``local.conf`` +--------------------------------------- + +Probably the easiest way to customize an image is to add a package by +way of the ``local.conf`` configuration file. Because it is limited to +local use, this method generally only allows you to add packages and is +not as flexible as creating your own customized image. When you add +packages using local variables this way, you need to realize that these +variable changes are in effect for every build and consequently affect +all images, which might not be what you require. + +To add a package to your image using the local configuration file, use +the ``IMAGE_INSTALL`` variable with the ``_append`` operator: +:: + + IMAGE_INSTALL_append = " strace" + +Use of the syntax is important - +specifically, the space between the quote and the package name, which is +``strace`` in this example. This space is required since the ``_append`` +operator does not add the space. + +Furthermore, you must use ``_append`` instead of the ``+=`` operator if +you want to avoid ordering issues. The reason for this is because doing +so unconditionally appends to the variable and avoids ordering problems +due to the variable being set in image recipes and ``.bbclass`` files +with operators like ``?=``. Using ``_append`` ensures the operation +takes effect. + +As shown in its simplest use, ``IMAGE_INSTALL_append`` affects all +images. It is possible to extend the syntax so that the variable applies +to a specific image only. Here is an example: +:: + + IMAGE_INSTALL_append_pn-core-image-minimal = " strace" + +This example adds ``strace`` to the ``core-image-minimal`` image only. + +You can add packages using a similar approach through the +``CORE_IMAGE_EXTRA_INSTALL`` variable. If you use this variable, only +``core-image-*`` images are affected. + +Customizing Images Using Custom ``IMAGE_FEATURES`` and ``EXTRA_IMAGE_FEATURES`` +------------------------------------------------------------------------------- + +Another method for customizing your image is to enable or disable +high-level image features by using the +:term:`IMAGE_FEATURES` and +:term:`EXTRA_IMAGE_FEATURES` +variables. Although the functions for both variables are nearly +equivalent, best practices dictate using ``IMAGE_FEATURES`` from within +a recipe and using ``EXTRA_IMAGE_FEATURES`` from within your +``local.conf`` file, which is found in the +:term:`Build Directory`. + +To understand how these features work, the best reference is +``meta/classes/core-image.bbclass``. This class lists out the available +``IMAGE_FEATURES`` of which most map to package groups while some, such +as ``debug-tweaks`` and ``read-only-rootfs``, resolve as general +configuration settings. + +In summary, the file looks at the contents of the ``IMAGE_FEATURES`` +variable and then maps or configures the feature accordingly. Based on +this information, the build system automatically adds the appropriate +packages or configurations to the +:term:`IMAGE_INSTALL` variable. +Effectively, you are enabling extra features by extending the class or +creating a custom class for use with specialized image ``.bb`` files. + +Use the ``EXTRA_IMAGE_FEATURES`` variable from within your local +configuration file. Using a separate area from which to enable features +with this variable helps you avoid overwriting the features in the image +recipe that are enabled with ``IMAGE_FEATURES``. The value of +``EXTRA_IMAGE_FEATURES`` is added to ``IMAGE_FEATURES`` within +``meta/conf/bitbake.conf``. + +To illustrate how you can use these variables to modify your image, +consider an example that selects the SSH server. The Yocto Project ships +with two SSH servers you can use with your images: Dropbear and OpenSSH. +Dropbear is a minimal SSH server appropriate for resource-constrained +environments, while OpenSSH is a well-known standard SSH server +implementation. By default, the ``core-image-sato`` image is configured +to use Dropbear. The ``core-image-full-cmdline`` and ``core-image-lsb`` +images both include OpenSSH. The ``core-image-minimal`` image does not +contain an SSH server. + +You can customize your image and change these defaults. Edit the +``IMAGE_FEATURES`` variable in your recipe or use the +``EXTRA_IMAGE_FEATURES`` in your ``local.conf`` file so that it +configures the image you are working with to include +``ssh-server-dropbear`` or ``ssh-server-openssh``. + +.. note:: + + See the ":ref:`ref-manual/ref-features:image features`" section in the Yocto + Project Reference Manual for a complete list of image features that ship + with the Yocto Project. + +Customizing Images Using Custom .bb Files +----------------------------------------- + +You can also customize an image by creating a custom recipe that defines +additional software as part of the image. The following example shows +the form for the two lines you need: +:: + + IMAGE_INSTALL = "packagegroup-core-x11-base package1 package2" + inherit core-image + +Defining the software using a custom recipe gives you total control over +the contents of the image. It is important to use the correct names of +packages in the ``IMAGE_INSTALL`` variable. You must use the +OpenEmbedded notation and not the Debian notation for the names (e.g. +``glibc-dev`` instead of ``libc6-dev``). + +The other method for creating a custom image is to base it on an +existing image. For example, if you want to create an image based on +``core-image-sato`` but add the additional package ``strace`` to the +image, copy the ``meta/recipes-sato/images/core-image-sato.bb`` to a new +``.bb`` and add the following line to the end of the copy: +:: + + IMAGE_INSTALL += "strace" + +Customizing Images Using Custom Package Groups +---------------------------------------------- + +For complex custom images, the best approach for customizing an image is +to create a custom package group recipe that is used to build the image +or images. A good example of a package group recipe is +``meta/recipes-core/packagegroups/packagegroup-base.bb``. + +If you examine that recipe, you see that the ``PACKAGES`` variable lists +the package group packages to produce. The ``inherit packagegroup`` +statement sets appropriate default values and automatically adds +``-dev``, ``-dbg``, and ``-ptest`` complementary packages for each +package specified in the ``PACKAGES`` statement. + +.. note:: + + The ``inherit packagegroup`` line should be located near the top of the + recipe, certainly before the ``PACKAGES`` statement. + +For each package you specify in ``PACKAGES``, you can use ``RDEPENDS`` +and ``RRECOMMENDS`` entries to provide a list of packages the parent +task package should contain. You can see examples of these further down +in the ``packagegroup-base.bb`` recipe. + +Here is a short, fabricated example showing the same basic pieces for a +hypothetical packagegroup defined in ``packagegroup-custom.bb``, where +the variable ``PN`` is the standard way to abbreviate the reference to +the full packagegroup name ``packagegroup-custom``: +:: + + DESCRIPTION = "My Custom Package Groups" + + inherit packagegroup + + PACKAGES = "\ + ${PN}-apps \ + ${PN}-tools \ + " + + RDEPENDS_${PN}-apps = "\ + dropbear \ + portmap \ + psplash" + + RDEPENDS_${PN}-tools = "\ + oprofile \ + oprofileui-server \ + lttng-tools" + + RRECOMMENDS_${PN}-tools = "\ + kernel-module-oprofile" + +In the previous example, two package group packages are created with +their dependencies and their recommended package dependencies listed: +``packagegroup-custom-apps``, and ``packagegroup-custom-tools``. To +build an image using these package group packages, you need to add +``packagegroup-custom-apps`` and/or ``packagegroup-custom-tools`` to +``IMAGE_INSTALL``. For other forms of image dependencies see the other +areas of this section. + +Customizing an Image Hostname +----------------------------- + +By default, the configured hostname (i.e. ``/etc/hostname``) in an image +is the same as the machine name. For example, if +:term:`MACHINE` equals "qemux86", the +configured hostname written to ``/etc/hostname`` is "qemux86". + +You can customize this name by altering the value of the "hostname" +variable in the ``base-files`` recipe using either an append file or a +configuration file. Use the following in an append file: +:: + + hostname = "myhostname" + +Use the following in a configuration file: +:: + + hostname_pn-base-files = "myhostname" + +Changing the default value of the variable "hostname" can be useful in +certain situations. For example, suppose you need to do extensive +testing on an image and you would like to easily identify the image +under test from existing images with typical default hostnames. In this +situation, you could change the default hostname to "testme", which +results in all the images using the name "testme". Once testing is +complete and you do not need to rebuild the image for test any longer, +you can easily reset the default hostname. + +Another point of interest is that if you unset the variable, the image +will have no default hostname in the filesystem. Here is an example that +unsets the variable in a configuration file: +:: + + hostname_pn-base-files = "" + +Having no default hostname in the filesystem is suitable for +environments that use dynamic hostnames such as virtual machines. + +Writing a New Recipe +==================== + +Recipes (``.bb`` files) are fundamental components in the Yocto Project +environment. Each software component built by the OpenEmbedded build +system requires a recipe to define the component. This section describes +how to create, write, and test a new recipe. + +.. note:: + + For information on variables that are useful for recipes and for + information about recipe naming issues, see the + ":ref:`ref-manual/ref-varlocality:recipes`" section of the Yocto Project + Reference Manual. + +Overview +-------- + +The following figure shows the basic process for creating a new recipe. +The remainder of the section provides details for the steps. + +.. image:: figures/recipe-workflow.png + :align: center + +Locate or Automatically Create a Base Recipe +-------------------------------------------- + +You can always write a recipe from scratch. However, three choices exist +that can help you quickly get a start on a new recipe: + +- ``devtool add``: A command that assists in creating a recipe and an + environment conducive to development. + +- ``recipetool create``: A command provided by the Yocto Project that + automates creation of a base recipe based on the source files. + +- *Existing Recipes:* Location and modification of an existing recipe + that is similar in function to the recipe you need. + +.. note:: + + For information on recipe syntax, see the + ":ref:`dev-manual/common-tasks:recipe syntax`" section. + +Creating the Base Recipe Using ``devtool add`` +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``devtool add`` command uses the same logic for auto-creating the +recipe as ``recipetool create``, which is listed below. Additionally, +however, ``devtool add`` sets up an environment that makes it easy for +you to patch the source and to make changes to the recipe as is often +necessary when adding a recipe to build a new piece of software to be +included in a build. + +You can find a complete description of the ``devtool add`` command in +the ":ref:`sdk-manual/sdk-extensible:a closer look at \`\`devtool add\`\``" section +in the Yocto Project Application Development and the Extensible Software +Development Kit (eSDK) manual. + +Creating the Base Recipe Using ``recipetool create`` +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +``recipetool create`` automates creation of a base recipe given a set of +source code files. As long as you can extract or point to the source +files, the tool will construct a recipe and automatically configure all +pre-build information into the recipe. For example, suppose you have an +application that builds using Autotools. Creating the base recipe using +``recipetool`` results in a recipe that has the pre-build dependencies, +license requirements, and checksums configured. + +To run the tool, you just need to be in your +:term:`Build Directory` and have sourced the +build environment setup script (i.e. +:ref:`structure-core-script`). +To get help on the tool, use the following command: +:: + + $ recipetool -h + NOTE: Starting bitbake server... + usage: recipetool [-d] [-q] [--color COLOR] [-h] <subcommand> ... + + OpenEmbedded recipe tool + + options: + -d, --debug Enable debug output + -q, --quiet Print only errors + --color COLOR Colorize output (where COLOR is auto, always, never) + -h, --help show this help message and exit + + subcommands: + create Create a new recipe + newappend Create a bbappend for the specified target in the specified + layer + setvar Set a variable within a recipe + appendfile Create/update a bbappend to replace a target file + appendsrcfiles Create/update a bbappend to add or replace source files + appendsrcfile Create/update a bbappend to add or replace a source file + Use recipetool <subcommand> --help to get help on a specific command + +Running ``recipetool create -o OUTFILE`` creates the base recipe and +locates it properly in the layer that contains your source files. +Following are some syntax examples: + + - Use this syntax to generate a recipe based on source. Once generated, + the recipe resides in the existing source code layer: + :: + + recipetool create -o OUTFILE source + + - Use this syntax to generate a recipe using code that + you extract from source. The extracted code is placed in its own layer + defined by ``EXTERNALSRC``. + :: + + recipetool create -o OUTFILE -x EXTERNALSRC source + + - Use this syntax to generate a recipe based on source. The options + direct ``recipetool`` to generate debugging information. Once generated, + the recipe resides in the existing source code layer: + :: + + recipetool create -d -o OUTFILE source + +Locating and Using a Similar Recipe +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Before writing a recipe from scratch, it is often useful to discover +whether someone else has already written one that meets (or comes close +to meeting) your needs. The Yocto Project and OpenEmbedded communities +maintain many recipes that might be candidates for what you are doing. +You can find a good central index of these recipes in the `OpenEmbedded +Layer Index <https://layers.openembedded.org>`__. + +Working from an existing recipe or a skeleton recipe is the best way to +get started. Here are some points on both methods: + +- *Locate and modify a recipe that is close to what you want to do:* + This method works when you are familiar with the current recipe + space. The method does not work so well for those new to the Yocto + Project or writing recipes. + + Some risks associated with this method are using a recipe that has + areas totally unrelated to what you are trying to accomplish with + your recipe, not recognizing areas of the recipe that you might have + to add from scratch, and so forth. All these risks stem from + unfamiliarity with the existing recipe space. + +- *Use and modify the following skeleton recipe:* If for some reason + you do not want to use ``recipetool`` and you cannot find an existing + recipe that is close to meeting your needs, you can use the following + structure to provide the fundamental areas of a new recipe. + :: + + DESCRIPTION = "" + HOMEPAGE = "" + LICENSE = "" + SECTION = "" + DEPENDS = "" + LIC_FILES_CHKSUM = "" + + SRC_URI = "" + +Storing and Naming the Recipe +----------------------------- + +Once you have your base recipe, you should put it in your own layer and +name it appropriately. Locating it correctly ensures that the +OpenEmbedded build system can find it when you use BitBake to process +the recipe. + +- *Storing Your Recipe:* The OpenEmbedded build system locates your + recipe through the layer's ``conf/layer.conf`` file and the + :term:`BBFILES` variable. This + variable sets up a path from which the build system can locate + recipes. Here is the typical use: + :: + + BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \ + ${LAYERDIR}/recipes-*/*/*.bbappend" + + Consequently, you need to be sure you locate your new recipe inside + your layer such that it can be found. + + You can find more information on how layers are structured in the + "`Understanding and Creating + Layers <#understanding-and-creating-layers>`__" section. + +- *Naming Your Recipe:* When you name your recipe, you need to follow + this naming convention: + :: + + basename_version.bb + + Use lower-cased characters and do not include the reserved suffixes + ``-native``, ``-cross``, ``-initial``, or ``-dev`` casually (i.e. do not use + them as part of your recipe name unless the string applies). Here are some + examples: + + .. code-block:: none + + cups_1.7.0.bb + gawk_4.0.2.bb + irssi_0.8.16-rc1.bb + +Running a Build on the Recipe +----------------------------- + +Creating a new recipe is usually an iterative process that requires +using BitBake to process the recipe multiple times in order to +progressively discover and add information to the recipe file. + +Assuming you have sourced the build environment setup script (i.e. +:ref:`structure-core-script`) and you are in +the :term:`Build Directory`, use +BitBake to process your recipe. All you need to provide is the +``basename`` of the recipe as described in the previous section: +:: + + $ bitbake basename + +During the build, the OpenEmbedded build system creates a temporary work +directory for each recipe +(``${``\ :term:`WORKDIR`\ ``}``) +where it keeps extracted source files, log files, intermediate +compilation and packaging files, and so forth. + +The path to the per-recipe temporary work directory depends on the +context in which it is being built. The quickest way to find this path +is to have BitBake return it by running the following: +:: + + $ bitbake -e basename | grep ^WORKDIR= + +As an example, assume a Source Directory +top-level folder named ``poky``, a default Build Directory at +``poky/build``, and a ``qemux86-poky-linux`` machine target system. +Furthermore, suppose your recipe is named ``foo_1.3.0.bb``. In this +case, the work directory the build system uses to build the package +would be as follows: +:: + + poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0 + +Inside this directory you can find sub-directories such as ``image``, +``packages-split``, and ``temp``. After the build, you can examine these +to determine how well the build went. + +.. note:: + + You can find log files for each task in the recipe's ``temp`` + directory (e.g. ``poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0/temp``). + Log files are named ``log.taskname`` (e.g. ``log.do_configure``, + ``log.do_fetch``, and ``log.do_compile``). + +You can find more information about the build process in +":doc:`/overview-manual/overview-manual-development-environment`" +chapter of the Yocto Project Overview and Concepts Manual. + +Fetching Code +------------- + +The first thing your recipe must do is specify how to fetch the source +files. Fetching is controlled mainly through the +:term:`SRC_URI` variable. Your recipe +must have a ``SRC_URI`` variable that points to where the source is +located. For a graphical representation of source locations, see the +":ref:`overview-manual/overview-manual-concepts:sources`" section in +the Yocto Project Overview and Concepts Manual. + +The :ref:`ref-tasks-fetch` task uses +the prefix of each entry in the ``SRC_URI`` variable value to determine +which :ref:`fetcher <bitbake:bitbake-user-manual/bitbake-user-manual-fetching:fetchers>` to use to get your +source files. It is the ``SRC_URI`` variable that triggers the fetcher. +The :ref:`ref-tasks-patch` task uses +the variable after source is fetched to apply patches. The OpenEmbedded +build system uses +:term:`FILESOVERRIDES` for +scanning directory locations for local files in ``SRC_URI``. + +The ``SRC_URI`` variable in your recipe must define each unique location +for your source files. It is good practice to not hard-code version +numbers in a URL used in ``SRC_URI``. Rather than hard-code these +values, use ``${``\ :term:`PV`\ ``}``, +which causes the fetch process to use the version specified in the +recipe filename. Specifying the version in this manner means that +upgrading the recipe to a future version is as simple as renaming the +recipe to match the new version. + +Here is a simple example from the +``meta/recipes-devtools/strace/strace_5.5.bb`` recipe where the source +comes from a single tarball. Notice the use of the +:term:`PV` variable: +:: + + SRC_URI = "https://strace.io/files/${PV}/strace-${PV}.tar.xz \ + +Files mentioned in ``SRC_URI`` whose names end in a typical archive +extension (e.g. ``.tar``, ``.tar.gz``, ``.tar.bz2``, ``.zip``, and so +forth), are automatically extracted during the +:ref:`ref-tasks-unpack` task. For +another example that specifies these types of files, see the +"`Autotooled Package <#new-recipe-autotooled-package>`__" section. + +Another way of specifying source is from an SCM. For Git repositories, +you must specify :term:`SRCREV` and +you should specify :term:`PV` to include +the revision with :term:`SRCPV`. Here +is an example from the recipe +``meta/recipes-kernel/blktrace/blktrace_git.bb``: +:: + + SRCREV = "d6918c8832793b4205ed3bfede78c2f915c23385" + + PR = "r6" + PV = "1.0.5+git${SRCPV}" + + SRC_URI = "git://git.kernel.dk/blktrace.git \ + file://ldflags.patch" + +If your ``SRC_URI`` statement includes URLs pointing to individual files +fetched from a remote server other than a version control system, +BitBake attempts to verify the files against checksums defined in your +recipe to ensure they have not been tampered with or otherwise modified +since the recipe was written. Two checksums are used: +``SRC_URI[md5sum]`` and ``SRC_URI[sha256sum]``. + +If your ``SRC_URI`` variable points to more than a single URL (excluding +SCM URLs), you need to provide the ``md5`` and ``sha256`` checksums for +each URL. For these cases, you provide a name for each URL as part of +the ``SRC_URI`` and then reference that name in the subsequent checksum +statements. Here is an example combining lines from the files +``git.inc`` and ``git_2.24.1.bb``: +:: + + SRC_URI = "${KERNELORG_MIRROR}/software/scm/git/git-${PV}.tar.gz;name=tarball \ + ${KERNELORG_MIRROR}/software/scm/git/git-manpages-${PV}.tar.gz;name=manpages" + + SRC_URI[tarball.md5sum] = "166bde96adbbc11c8843d4f8f4f9811b" + SRC_URI[tarball.sha256sum] = "ad5334956301c86841eb1e5b1bb20884a6bad89a10a6762c958220c7cf64da02" + SRC_URI[manpages.md5sum] = "31c2272a8979022497ba3d4202df145d" + SRC_URI[manpages.sha256sum] = "9a7ae3a093bea39770eb96ca3e5b40bff7af0b9f6123f089d7821d0e5b8e1230" + +Proper values for ``md5`` and ``sha256`` checksums might be available +with other signatures on the download page for the upstream source (e.g. +``md5``, ``sha1``, ``sha256``, ``GPG``, and so forth). Because the +OpenEmbedded build system only deals with ``sha256sum`` and ``md5sum``, +you should verify all the signatures you find by hand. + +If no ``SRC_URI`` checksums are specified when you attempt to build the +recipe, or you provide an incorrect checksum, the build will produce an +error for each missing or incorrect checksum. As part of the error +message, the build system provides the checksum string corresponding to +the fetched file. Once you have the correct checksums, you can copy and +paste them into your recipe and then run the build again to continue. + +.. note:: + + As mentioned, if the upstream source provides signatures for + verifying the downloaded source code, you should verify those + manually before setting the checksum values in the recipe and + continuing with the build. + +This final example is a bit more complicated and is from the +``meta/recipes-sato/rxvt-unicode/rxvt-unicode_9.20.bb`` recipe. The +example's ``SRC_URI`` statement identifies multiple files as the source +files for the recipe: a tarball, a patch file, a desktop file, and an +icon. +:: + + SRC_URI = "http://dist.schmorp.de/rxvt-unicode/Attic/rxvt-unicode-${PV}.tar.bz2 \ + file://xwc.patch \ + file://rxvt.desktop \ + file://rxvt.png" + +When you specify local files using the ``file://`` URI protocol, the +build system fetches files from the local machine. The path is relative +to the :term:`FILESPATH` variable +and searches specific directories in a certain order: +``${``\ :term:`BP`\ ``}``, +``${``\ :term:`BPN`\ ``}``, and +``files``. The directories are assumed to be subdirectories of the +directory in which the recipe or append file resides. For another +example that specifies these types of files, see the "`Single .c File +Package (Hello +World!) <#new-recipe-single-c-file-package-hello-world>`__" section. + +The previous example also specifies a patch file. Patch files are files +whose names usually end in ``.patch`` or ``.diff`` but can end with +compressed suffixes such as ``diff.gz`` and ``patch.bz2``, for example. +The build system automatically applies patches as described in the +"`Patching Code <#new-recipe-patching-code>`__" section. + +Unpacking Code +-------------- + +During the build, the +:ref:`ref-tasks-unpack` task unpacks +the source with ``${``\ :term:`S`\ ``}`` +pointing to where it is unpacked. + +If you are fetching your source files from an upstream source archived +tarball and the tarball's internal structure matches the common +convention of a top-level subdirectory named +``${``\ :term:`BPN`\ ``}-${``\ :term:`PV`\ ``}``, +then you do not need to set ``S``. However, if ``SRC_URI`` specifies to +fetch source from an archive that does not use this convention, or from +an SCM like Git or Subversion, your recipe needs to define ``S``. + +If processing your recipe using BitBake successfully unpacks the source +files, you need to be sure that the directory pointed to by ``${S}`` +matches the structure of the source. + +Patching Code +------------- + +Sometimes it is necessary to patch code after it has been fetched. Any +files mentioned in ``SRC_URI`` whose names end in ``.patch`` or +``.diff`` or compressed versions of these suffixes (e.g. ``diff.gz`` are +treated as patches. The +:ref:`ref-tasks-patch` task +automatically applies these patches. + +The build system should be able to apply patches with the "-p1" option +(i.e. one directory level in the path will be stripped off). If your +patch needs to have more directory levels stripped off, specify the +number of levels using the "striplevel" option in the ``SRC_URI`` entry +for the patch. Alternatively, if your patch needs to be applied in a +specific subdirectory that is not specified in the patch file, use the +"patchdir" option in the entry. + +As with all local files referenced in +:term:`SRC_URI` using ``file://``, +you should place patch files in a directory next to the recipe either +named the same as the base name of the recipe +(:term:`BP` and +:term:`BPN`) or "files". + +Licensing +--------- + +Your recipe needs to have both the +:term:`LICENSE` and +:term:`LIC_FILES_CHKSUM` +variables: + +- ``LICENSE``: This variable specifies the license for the software. + If you do not know the license under which the software you are + building is distributed, you should go to the source code and look + for that information. Typical files containing this information + include ``COPYING``, ``LICENSE``, and ``README`` files. You could + also find the information near the top of a source file. For example, + given a piece of software licensed under the GNU General Public + License version 2, you would set ``LICENSE`` as follows: + :: + + LICENSE = "GPLv2" + + The licenses you specify within ``LICENSE`` can have any name as long + as you do not use spaces, since spaces are used as separators between + license names. For standard licenses, use the names of the files in + ``meta/files/common-licenses/`` or the ``SPDXLICENSEMAP`` flag names + defined in ``meta/conf/licenses.conf``. + +- ``LIC_FILES_CHKSUM``: The OpenEmbedded build system uses this + variable to make sure the license text has not changed. If it has, + the build produces an error and it affords you the chance to figure + it out and correct the problem. + + You need to specify all applicable licensing files for the software. + At the end of the configuration step, the build process will compare + the checksums of the files to be sure the text has not changed. Any + differences result in an error with the message containing the + current checksum. For more explanation and examples of how to set the + ``LIC_FILES_CHKSUM`` variable, see the + ":ref:`dev-manual/common-tasks:tracking license changes`" section. + + To determine the correct checksum string, you can list the + appropriate files in the ``LIC_FILES_CHKSUM`` variable with incorrect + md5 strings, attempt to build the software, and then note the + resulting error messages that will report the correct md5 strings. + See the "`Fetching Code <#new-recipe-fetching-code>`__" section for + additional information. + + Here is an example that assumes the software has a ``COPYING`` file: + :: + + LIC_FILES_CHKSUM = "file://COPYING;md5=xxx" + + When you try to build the + software, the build system will produce an error and give you the + correct string that you can substitute into the recipe file for a + subsequent build. + +Dependencies +------------ + +Most software packages have a short list of other packages that they +require, which are called dependencies. These dependencies fall into two +main categories: build-time dependencies, which are required when the +software is built; and runtime dependencies, which are required to be +installed on the target in order for the software to run. + +Within a recipe, you specify build-time dependencies using the +:term:`DEPENDS` variable. Although +nuances exist, items specified in ``DEPENDS`` should be names of other +recipes. It is important that you specify all build-time dependencies +explicitly. + +Another consideration is that configure scripts might automatically +check for optional dependencies and enable corresponding functionality +if those dependencies are found. If you wish to make a recipe that is +more generally useful (e.g. publish the recipe in a layer for others to +use), instead of hard-disabling the functionality, you can use the +:term:`PACKAGECONFIG` variable to allow functionality and the +corresponding dependencies to be enabled and disabled easily by other +users of the recipe. + +Similar to build-time dependencies, you specify runtime dependencies +through a variable - +:term:`RDEPENDS`, which is +package-specific. All variables that are package-specific need to have +the name of the package added to the end as an override. Since the main +package for a recipe has the same name as the recipe, and the recipe's +name can be found through the +``${``\ :term:`PN`\ ``}`` variable, then +you specify the dependencies for the main package by setting +``RDEPENDS_${PN}``. If the package were named ``${PN}-tools``, then you +would set ``RDEPENDS_${PN}-tools``, and so forth. + +Some runtime dependencies will be set automatically at packaging time. +These dependencies include any shared library dependencies (i.e. if a +package "example" contains "libexample" and another package "mypackage" +contains a binary that links to "libexample" then the OpenEmbedded build +system will automatically add a runtime dependency to "mypackage" on +"example"). See the +":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`" +section in the Yocto Project Overview and Concepts Manual for further +details. + +Configuring the Recipe +---------------------- + +Most software provides some means of setting build-time configuration +options before compilation. Typically, setting these options is +accomplished by running a configure script with options, or by modifying +a build configuration file. + +.. note:: + + As of Yocto Project Release 1.7, some of the core recipes that + package binary configuration scripts now disable the scripts due to + the scripts previously requiring error-prone path substitution. The + OpenEmbedded build system uses ``pkg-config`` now, which is much more + robust. You can find a list of the ``*-config`` scripts that are disabled + in the ":ref:`migration-1.7-binary-configuration-scripts-disabled`" section + in the Yocto Project Reference Manual. + +A major part of build-time configuration is about checking for +build-time dependencies and possibly enabling optional functionality as +a result. You need to specify any build-time dependencies for the +software you are building in your recipe's +:term:`DEPENDS` value, in terms of +other recipes that satisfy those dependencies. You can often find +build-time or runtime dependencies described in the software's +documentation. + +The following list provides configuration items of note based on how +your software is built: + +- *Autotools:* If your source files have a ``configure.ac`` file, then + your software is built using Autotools. If this is the case, you just + need to worry about modifying the configuration. + + When using Autotools, your recipe needs to inherit the + :ref:`autotools <ref-classes-autotools>` class + and your recipe does not have to contain a + :ref:`ref-tasks-configure` task. + However, you might still want to make some adjustments. For example, + you can set + :term:`EXTRA_OECONF` or + :term:`PACKAGECONFIG_CONFARGS` + to pass any needed configure options that are specific to the recipe. + +- *CMake:* If your source files have a ``CMakeLists.txt`` file, then + your software is built using CMake. If this is the case, you just + need to worry about modifying the configuration. + + When you use CMake, your recipe needs to inherit the + :ref:`cmake <ref-classes-cmake>` class and your + recipe does not have to contain a + :ref:`ref-tasks-configure` task. + You can make some adjustments by setting + :term:`EXTRA_OECMAKE` to + pass any needed configure options that are specific to the recipe. + + .. note:: + + If you need to install one or more custom CMake toolchain files + that are supplied by the application you are building, install the + files to ``${D}${datadir}/cmake/Modules`` during ``do_install``. + +- *Other:* If your source files do not have a ``configure.ac`` or + ``CMakeLists.txt`` file, then your software is built using some + method other than Autotools or CMake. If this is the case, you + normally need to provide a + :ref:`ref-tasks-configure` task + in your recipe unless, of course, there is nothing to configure. + + Even if your software is not being built by Autotools or CMake, you + still might not need to deal with any configuration issues. You need + to determine if configuration is even a required step. You might need + to modify a Makefile or some configuration file used for the build to + specify necessary build options. Or, perhaps you might need to run a + provided, custom configure script with the appropriate options. + + For the case involving a custom configure script, you would run + ``./configure --help`` and look for the options you need to set. + +Once configuration succeeds, it is always good practice to look at the +``log.do_configure`` file to ensure that the appropriate options have +been enabled and no additional build-time dependencies need to be added +to ``DEPENDS``. For example, if the configure script reports that it +found something not mentioned in ``DEPENDS``, or that it did not find +something that it needed for some desired optional functionality, then +you would need to add those to ``DEPENDS``. Looking at the log might +also reveal items being checked for, enabled, or both that you do not +want, or items not being found that are in ``DEPENDS``, in which case +you would need to look at passing extra options to the configure script +as needed. For reference information on configure options specific to +the software you are building, you can consult the output of the +``./configure --help`` command within ``${S}`` or consult the software's +upstream documentation. + +Using Headers to Interface with Devices +--------------------------------------- + +If your recipe builds an application that needs to communicate with some +device or needs an API into a custom kernel, you will need to provide +appropriate header files. Under no circumstances should you ever modify +the existing +``meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc`` file. +These headers are used to build ``libc`` and must not be compromised +with custom or machine-specific header information. If you customize +``libc`` through modified headers all other applications that use +``libc`` thus become affected. + +.. note:: + + Never copy and customize the ``libc`` header file (i.e. + ``meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc``). + +The correct way to interface to a device or custom kernel is to use a +separate package that provides the additional headers for the driver or +other unique interfaces. When doing so, your application also becomes +responsible for creating a dependency on that specific provider. + +Consider the following: + +- Never modify ``linux-libc-headers.inc``. Consider that file to be + part of the ``libc`` system, and not something you use to access the + kernel directly. You should access ``libc`` through specific ``libc`` + calls. + +- Applications that must talk directly to devices should either provide + necessary headers themselves, or establish a dependency on a special + headers package that is specific to that driver. + +For example, suppose you want to modify an existing header that adds I/O +control or network support. If the modifications are used by a small +number programs, providing a unique version of a header is easy and has +little impact. When doing so, bear in mind the guidelines in the +previous list. + +.. note:: + + If for some reason your changes need to modify the behavior of the ``libc``, + and subsequently all other applications on the system, use a ``.bbappend`` + to modify the ``linux-kernel-headers.inc`` file. However, take care to not + make the changes machine specific. + +Consider a case where your kernel is older and you need an older +``libc`` ABI. The headers installed by your recipe should still be a +standard mainline kernel, not your own custom one. + +When you use custom kernel headers you need to get them from +:term:`STAGING_KERNEL_DIR`, +which is the directory with kernel headers that are required to build +out-of-tree modules. Your recipe will also need the following: +:: + + do_configure[depends] += "virtual/kernel:do_shared_workdir" + +Compilation +----------- + +During a build, the ``do_compile`` task happens after source is fetched, +unpacked, and configured. If the recipe passes through ``do_compile`` +successfully, nothing needs to be done. + +However, if the compile step fails, you need to diagnose the failure. +Here are some common issues that cause failures. + +.. note:: + + For cases where improper paths are detected for configuration files + or for when libraries/headers cannot be found, be sure you are using + the more robust ``pkg-config``. See the note in section + ":ref:`dev-manual/common-tasks:Configuring the Recipe`" for additional information. + +- *Parallel build failures:* These failures manifest themselves as + intermittent errors, or errors reporting that a file or directory + that should be created by some other part of the build process could + not be found. This type of failure can occur even if, upon + inspection, the file or directory does exist after the build has + failed, because that part of the build process happened in the wrong + order. + + To fix the problem, you need to either satisfy the missing dependency + in the Makefile or whatever script produced the Makefile, or (as a + workaround) set :term:`PARALLEL_MAKE` to an empty string: + :: + + PARALLEL_MAKE = "" + + For information on parallel Makefile issues, see the "`Debugging + Parallel Make Races <#debugging-parallel-make-races>`__" section. + +- *Improper host path usage:* This failure applies to recipes building + for the target or ``nativesdk`` only. The failure occurs when the + compilation process uses improper headers, libraries, or other files + from the host system when cross-compiling for the target. + + To fix the problem, examine the ``log.do_compile`` file to identify + the host paths being used (e.g. ``/usr/include``, ``/usr/lib``, and + so forth) and then either add configure options, apply a patch, or do + both. + +- *Failure to find required libraries/headers:* If a build-time + dependency is missing because it has not been declared in + :term:`DEPENDS`, or because the + dependency exists but the path used by the build process to find the + file is incorrect and the configure step did not detect it, the + compilation process could fail. For either of these failures, the + compilation process notes that files could not be found. In these + cases, you need to go back and add additional options to the + configure script as well as possibly add additional build-time + dependencies to ``DEPENDS``. + + Occasionally, it is necessary to apply a patch to the source to + ensure the correct paths are used. If you need to specify paths to + find files staged into the sysroot from other recipes, use the + variables that the OpenEmbedded build system provides (e.g. + ``STAGING_BINDIR``, ``STAGING_INCDIR``, ``STAGING_DATADIR``, and so + forth). + +Installing +---------- + +During ``do_install``, the task copies the built files along with their +hierarchy to locations that would mirror their locations on the target +device. The installation process copies files from the +``${``\ :term:`S`\ ``}``, +``${``\ :term:`B`\ ``}``, and +``${``\ :term:`WORKDIR`\ ``}`` +directories to the ``${``\ :term:`D`\ ``}`` +directory to create the structure as it should appear on the target +system. + +How your software is built affects what you must do to be sure your +software is installed correctly. The following list describes what you +must do for installation depending on the type of build system used by +the software being built: + +- *Autotools and CMake:* If the software your recipe is building uses + Autotools or CMake, the OpenEmbedded build system understands how to + install the software. Consequently, you do not have to have a + ``do_install`` task as part of your recipe. You just need to make + sure the install portion of the build completes with no issues. + However, if you wish to install additional files not already being + installed by ``make install``, you should do this using a + ``do_install_append`` function using the install command as described + in the "Manual" bulleted item later in this list. + +- *Other (using* ``make install``\ *)*: You need to define a ``do_install`` + function in your recipe. The function should call + ``oe_runmake install`` and will likely need to pass in the + destination directory as well. How you pass that path is dependent on + how the ``Makefile`` being run is written (e.g. ``DESTDIR=${D}``, + ``PREFIX=${D}``, ``INSTALLROOT=${D}``, and so forth). + + For an example recipe using ``make install``, see the + "`Makefile-Based Package <#new-recipe-makefile-based-package>`__" + section. + +- *Manual:* You need to define a ``do_install`` function in your + recipe. The function must first use ``install -d`` to create the + directories under + ``${``\ :term:`D`\ ``}``. Once the + directories exist, your function can use ``install`` to manually + install the built software into the directories. + + You can find more information on ``install`` at + https://www.gnu.org/software/coreutils/manual/html_node/install-invocation.html. + +For the scenarios that do not use Autotools or CMake, you need to track +the installation and diagnose and fix any issues until everything +installs correctly. You need to look in the default location of +``${D}``, which is ``${WORKDIR}/image``, to be sure your files have been +installed correctly. + +.. note:: + + - During the installation process, you might need to modify some of + the installed files to suit the target layout. For example, you + might need to replace hard-coded paths in an initscript with + values of variables provided by the build system, such as + replacing ``/usr/bin/`` with ``${bindir}``. If you do perform such + modifications during ``do_install``, be sure to modify the + destination file after copying rather than before copying. + Modifying after copying ensures that the build system can + re-execute ``do_install`` if needed. + + - ``oe_runmake install``, which can be run directly or can be run + indirectly by the + :ref:`autotools <ref-classes-autotools>` and + :ref:`cmake <ref-classes-cmake>` classes, + runs ``make install`` in parallel. Sometimes, a Makefile can have + missing dependencies between targets that can result in race + conditions. If you experience intermittent failures during + ``do_install``, you might be able to work around them by disabling + parallel Makefile installs by adding the following to the recipe: + :: + + PARALLEL_MAKEINST = "" + + See :term:`PARALLEL_MAKEINST` for additional information. + + - If you need to install one or more custom CMake toolchain files + that are supplied by the application you are building, install the + files to ``${D}${datadir}/cmake/Modules`` during + :ref:`ref-tasks-install`. + +Enabling System Services +------------------------ + +If you want to install a service, which is a process that usually starts +on boot and runs in the background, then you must include some +additional definitions in your recipe. + +If you are adding services and the service initialization script or the +service file itself is not installed, you must provide for that +installation in your recipe using a ``do_install_append`` function. If +your recipe already has a ``do_install`` function, update the function +near its end rather than adding an additional ``do_install_append`` +function. + +When you create the installation for your services, you need to +accomplish what is normally done by ``make install``. In other words, +make sure your installation arranges the output similar to how it is +arranged on the target system. + +The OpenEmbedded build system provides support for starting services two +different ways: + +- *SysVinit:* SysVinit is a system and service manager that manages the + init system used to control the very basic functions of your system. + The init program is the first program started by the Linux kernel + when the system boots. Init then controls the startup, running and + shutdown of all other programs. + + To enable a service using SysVinit, your recipe needs to inherit the + :ref:`update-rc.d <ref-classes-update-rc.d>` + class. The class helps facilitate safely installing the package on + the target. + + You will need to set the + :term:`INITSCRIPT_PACKAGES`, + :term:`INITSCRIPT_NAME`, + and + :term:`INITSCRIPT_PARAMS` + variables within your recipe. + +- *systemd:* System Management Daemon (systemd) was designed to replace + SysVinit and to provide enhanced management of services. For more + information on systemd, see the systemd homepage at + https://freedesktop.org/wiki/Software/systemd/. + + To enable a service using systemd, your recipe needs to inherit the + :ref:`systemd <ref-classes-systemd>` class. See + the ``systemd.bbclass`` file located in your :term:`Source Directory` + section for + more information. + +Packaging +--------- + +Successful packaging is a combination of automated processes performed +by the OpenEmbedded build system and some specific steps you need to +take. The following list describes the process: + +- *Splitting Files*: The ``do_package`` task splits the files produced + by the recipe into logical components. Even software that produces a + single binary might still have debug symbols, documentation, and + other logical components that should be split out. The ``do_package`` + task ensures that files are split up and packaged correctly. + +- *Running QA Checks*: The + :ref:`insane <ref-classes-insane>` class adds a + step to the package generation process so that output quality + assurance checks are generated by the OpenEmbedded build system. This + step performs a range of checks to be sure the build's output is free + of common problems that show up during runtime. For information on + these checks, see the + :ref:`insane <ref-classes-insane>` class and + the ":ref:`ref-manual/ref-qa-checks:qa error and warning messages`" + chapter in the Yocto Project Reference Manual. + +- *Hand-Checking Your Packages*: After you build your software, you + need to be sure your packages are correct. Examine the + ``${``\ :term:`WORKDIR`\ ``}/packages-split`` + directory and make sure files are where you expect them to be. If you + discover problems, you can set + :term:`PACKAGES`, + :term:`FILES`, + ``do_install(_append)``, and so forth as needed. + +- *Splitting an Application into Multiple Packages*: If you need to + split an application into several packages, see the "`Splitting an + Application into Multiple + Packages <#splitting-an-application-into-multiple-packages>`__" + section for an example. + +- *Installing a Post-Installation Script*: For an example showing how + to install a post-installation script, see the "`Post-Installation + Scripts <#new-recipe-post-installation-scripts>`__" section. + +- *Marking Package Architecture*: Depending on what your recipe is + building and how it is configured, it might be important to mark the + packages produced as being specific to a particular machine, or to + mark them as not being specific to a particular machine or + architecture at all. + + By default, packages apply to any machine with the same architecture + as the target machine. When a recipe produces packages that are + machine-specific (e.g. the + :term:`MACHINE` value is passed + into the configure script or a patch is applied only for a particular + machine), you should mark them as such by adding the following to the + recipe: + :: + + PACKAGE_ARCH = "${MACHINE_ARCH}" + + On the other hand, if the recipe produces packages that do not + contain anything specific to the target machine or architecture at + all (e.g. recipes that simply package script files or configuration + files), you should use the + :ref:`allarch <ref-classes-allarch>` class to + do this for you by adding this to your recipe: + :: + + inherit allarch + + Ensuring that the package architecture is correct is not critical + while you are doing the first few builds of your recipe. However, it + is important in order to ensure that your recipe rebuilds (or does + not rebuild) appropriately in response to changes in configuration, + and to ensure that you get the appropriate packages installed on the + target machine, particularly if you run separate builds for more than + one target machine. + +Sharing Files Between Recipes +----------------------------- + +Recipes often need to use files provided by other recipes on the build +host. For example, an application linking to a common library needs +access to the library itself and its associated headers. The way this +access is accomplished is by populating a sysroot with files. Each +recipe has two sysroots in its work directory, one for target files +(``recipe-sysroot``) and one for files that are native to the build host +(``recipe-sysroot-native``). + +.. note:: + + You could find the term "staging" used within the Yocto project + regarding files populating sysroots (e.g. the :term:`STAGING_DIR` + variable). + +Recipes should never populate the sysroot directly (i.e. write files +into sysroot). Instead, files should be installed into standard +locations during the +:ref:`ref-tasks-install` task within +the ``${``\ :term:`D`\ ``}`` directory. The +reason for this limitation is that almost all files that populate the +sysroot are cataloged in manifests in order to ensure the files can be +removed later when a recipe is either modified or removed. Thus, the +sysroot is able to remain free from stale files. + +A subset of the files installed by the +:ref:`ref-tasks-install` task are +used by the +:ref:`ref-tasks-populate_sysroot` +task as defined by the the +:term:`SYSROOT_DIRS` variable to +automatically populate the sysroot. It is possible to modify the list of +directories that populate the sysroot. The following example shows how +you could add the ``/opt`` directory to the list of directories within a +recipe: +:: + + SYSROOT_DIRS += "/opt" + +For a more complete description of the +:ref:`ref-tasks-populate_sysroot` +task and its associated functions, see the +:ref:`staging <ref-classes-staging>` class. + +Using Virtual Providers +----------------------- + +Prior to a build, if you know that several different recipes provide the +same functionality, you can use a virtual provider (i.e. ``virtual/*``) +as a placeholder for the actual provider. The actual provider is +determined at build-time. + +A common scenario where a virtual provider is used would be for the +kernel recipe. Suppose you have three kernel recipes whose +:term:`PN` values map to ``kernel-big``, +``kernel-mid``, and ``kernel-small``. Furthermore, each of these recipes +in some way uses a :term:`PROVIDES` +statement that essentially identifies itself as being able to provide +``virtual/kernel``. Here is one way through the +:ref:`kernel <ref-classes-kernel>` class: +:: + + PROVIDES += "${@ "virtual/kernel" if (d.getVar("KERNEL_PACKAGE_NAME") == "kernel") else "" }" + +Any recipe that inherits the ``kernel`` class is +going to utilize a ``PROVIDES`` statement that identifies that recipe as +being able to provide the ``virtual/kernel`` item. + +Now comes the time to actually build an image and you need a kernel +recipe, but which one? You can configure your build to call out the +kernel recipe you want by using the :term:`PREFERRED_PROVIDER` variable. As +an example, consider the :yocto_git:`x86-base.inc +</poky/tree/meta/conf/machine/include/x86-base.inc>` include file, which is a +machine (i.e. :term:`MACHINE`) configuration file. This include file is the +reason all x86-based machines use the ``linux-yocto`` kernel. Here are the +relevant lines from the include file: +:: + + PREFERRED_PROVIDER_virtual/kernel ??= "linux-yocto" + PREFERRED_VERSION_linux-yocto ??= "4.15%" + +When you use a virtual provider, you do not have to "hard code" a recipe +name as a build dependency. You can use the +:term:`DEPENDS` variable to state the +build is dependent on ``virtual/kernel`` for example: +:: + + DEPENDS = "virtual/kernel" + +During the build, the OpenEmbedded build system picks +the correct recipe needed for the ``virtual/kernel`` dependency based on +the ``PREFERRED_PROVIDER`` variable. If you want to use the small kernel +mentioned at the beginning of this section, configure your build as +follows: +:: + + PREFERRED_PROVIDER_virtual/kernel ??= "kernel-small" + +.. note:: + + Any recipe that ``PROVIDES`` a ``virtual/*`` item that is ultimately not + selected through ``PREFERRED_PROVIDER`` does not get built. Preventing these + recipes from building is usually the desired behavior since this mechanism's + purpose is to select between mutually exclusive alternative providers. + +The following lists specific examples of virtual providers: + +- ``virtual/kernel``: Provides the name of the kernel recipe to use + when building a kernel image. + +- ``virtual/bootloader``: Provides the name of the bootloader to use + when building an image. + +- ``virtual/libgbm``: Provides ``gbm.pc``. + +- ``virtual/egl``: Provides ``egl.pc`` and possibly ``wayland-egl.pc``. + +- ``virtual/libgl``: Provides ``gl.pc`` (i.e. libGL). + +- ``virtual/libgles1``: Provides ``glesv1_cm.pc`` (i.e. libGLESv1_CM). + +- ``virtual/libgles2``: Provides ``glesv2.pc`` (i.e. libGLESv2). + +.. note:: + + Virtual providers only apply to build time dependencies specified with + :term:`PROVIDES` and :term:`DEPENDS`. They do not apply to runtime + dependencies specified with :term:`RPROVIDES` and :term:`RDEPENDS`. + +Properly Versioning Pre-Release Recipes +--------------------------------------- + +Sometimes the name of a recipe can lead to versioning problems when the +recipe is upgraded to a final release. For example, consider the +``irssi_0.8.16-rc1.bb`` recipe file in the list of example recipes in +the "`Storing and Naming the +Recipe <#new-recipe-storing-and-naming-the-recipe>`__" section. This +recipe is at a release candidate stage (i.e. "rc1"). When the recipe is +released, the recipe filename becomes ``irssi_0.8.16.bb``. The version +change from ``0.8.16-rc1`` to ``0.8.16`` is seen as a decrease by the +build system and package managers, so the resulting packages will not +correctly trigger an upgrade. + +In order to ensure the versions compare properly, the recommended +convention is to set :term:`PV` within the +recipe to "previous_version+current_version". You can use an additional +variable so that you can use the current version elsewhere. Here is an +example: +:: + + REALPV = "0.8.16-rc1" + PV = "0.8.15+${REALPV}" + +Post-Installation Scripts +------------------------- + +Post-installation scripts run immediately after installing a package on +the target or during image creation when a package is included in an +image. To add a post-installation script to a package, add a +``pkg_postinst_``\ `PACKAGENAME`\ ``()`` function to the recipe file +(``.bb``) and replace `PACKAGENAME` with the name of the package you want +to attach to the ``postinst`` script. To apply the post-installation +script to the main package for the recipe, which is usually what is +required, specify +``${``\ :term:`PN`\ ``}`` in place of +PACKAGENAME. + +A post-installation function has the following structure: +:: + + pkg_postinst_PACKAGENAME() { + # Commands to carry out + } + +The script defined in the post-installation function is called when the +root filesystem is created. If the script succeeds, the package is +marked as installed. + +.. note:: + + Any RPM post-installation script that runs on the target should + return a 0 exit code. RPM does not allow non-zero exit codes for + these scripts, and the RPM package manager will cause the package to + fail installation on the target. + +Sometimes it is necessary for the execution of a post-installation +script to be delayed until the first boot. For example, the script might +need to be executed on the device itself. To delay script execution +until boot time, you must explicitly mark post installs to defer to the +target. You can use ``pkg_postinst_ontarget()`` or call +``postinst_intercept delay_to_first_boot`` from ``pkg_postinst()``. Any +failure of a ``pkg_postinst()`` script (including exit 1) triggers an +error during the +:ref:`ref-tasks-rootfs` task. + +If you have recipes that use ``pkg_postinst`` function and they require +the use of non-standard native tools that have dependencies during +rootfs construction, you need to use the +:term:`PACKAGE_WRITE_DEPS` +variable in your recipe to list these tools. If you do not use this +variable, the tools might be missing and execution of the +post-installation script is deferred until first boot. Deferring the +script to first boot is undesirable and for read-only rootfs impossible. + +.. note:: + + Equivalent support for pre-install, pre-uninstall, and post-uninstall + scripts exist by way of ``pkg_preinst``, ``pkg_prerm``, and ``pkg_postrm``, + respectively. These scrips work in exactly the same way as does + ``pkg_postinst`` with the exception that they run at different times. Also, + because of when they run, they are not applicable to being run at image + creation time like ``pkg_postinst``. + +Testing +------- + +The final step for completing your recipe is to be sure that the +software you built runs correctly. To accomplish runtime testing, add +the build's output packages to your image and test them on the target. + +For information on how to customize your image by adding specific +packages, see the "`Customizing +Images <#usingpoky-extend-customimage>`__" section. + +Examples +-------- + +To help summarize how to write a recipe, this section provides some +examples given various scenarios: + +- Recipes that use local files + +- Using an Autotooled package + +- Using a Makefile-based package + +- Splitting an application into multiple packages + +- Adding binaries to an image + +Single .c File Package (Hello World!) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Building an application from a single file that is stored locally (e.g. +under ``files``) requires a recipe that has the file listed in the +``SRC_URI`` variable. Additionally, you need to manually write the +``do_compile`` and ``do_install`` tasks. The ``S`` variable defines the +directory containing the source code, which is set to +:term:`WORKDIR` in this case - the +directory BitBake uses for the build. +:: + + SUMMARY = "Simple helloworld application" + SECTION = "examples" + LICENSE = "MIT" + LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302" + + SRC_URI = "file://helloworld.c" + + S = "${WORKDIR}" + + do_compile() { + ${CC} helloworld.c -o helloworld + } + + do_install() { + install -d ${D}${bindir} + install -m 0755 helloworld ${D}${bindir} + } + +By default, the ``helloworld``, ``helloworld-dbg``, and +``helloworld-dev`` packages are built. For information on how to +customize the packaging process, see the "`Splitting an Application into +Multiple Packages <#splitting-an-application-into-multiple-packages>`__" +section. + +Autotooled Package +~~~~~~~~~~~~~~~~~~ + +Applications that use Autotools such as ``autoconf`` and ``automake`` +require a recipe that has a source archive listed in ``SRC_URI`` and +also inherit the +:ref:`autotools <ref-classes-autotools>` class, +which contains the definitions of all the steps needed to build an +Autotool-based application. The result of the build is automatically +packaged. And, if the application uses NLS for localization, packages +with local information are generated (one package per language). +Following is one example: (``hello_2.3.bb``) +:: + + SUMMARY = "GNU Helloworld application" + SECTION = "examples" + LICENSE = "GPLv2+" + LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe" + + SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz" + + inherit autotools gettext + +The variable ``LIC_FILES_CHKSUM`` is used to track source license +changes as described in the +":ref:`dev-manual/common-tasks:tracking license changes`" section in +the Yocto Project Overview and Concepts Manual. You can quickly create +Autotool-based recipes in a manner similar to the previous example. + +Makefile-Based Package +~~~~~~~~~~~~~~~~~~~~~~ + +Applications that use GNU ``make`` also require a recipe that has the +source archive listed in ``SRC_URI``. You do not need to add a +``do_compile`` step since by default BitBake starts the ``make`` command +to compile the application. If you need additional ``make`` options, you +should store them in the +:term:`EXTRA_OEMAKE` or +:term:`PACKAGECONFIG_CONFARGS` +variables. BitBake passes these options into the GNU ``make`` +invocation. Note that a ``do_install`` task is still required. +Otherwise, BitBake runs an empty ``do_install`` task by default. + +Some applications might require extra parameters to be passed to the +compiler. For example, the application might need an additional header +path. You can accomplish this by adding to the ``CFLAGS`` variable. The +following example shows this: +:: + + CFLAGS_prepend = "-I ${S}/include " + +In the following example, ``mtd-utils`` is a makefile-based package: +:: + + SUMMARY = "Tools for managing memory technology devices" + SECTION = "base" + DEPENDS = "zlib lzo e2fsprogs util-linux" + HOMEPAGE = "http://www.linux-mtd.infradead.org/" + LICENSE = "GPLv2+" + LIC_FILES_CHKSUM = "file://COPYING;md5=0636e73ff0215e8d672dc4c32c317bb3 \ + file://include/common.h;beginline=1;endline=17;md5=ba05b07912a44ea2bf81ce409380049c" + + # Use the latest version at 26 Oct, 2013 + SRCREV = "9f107132a6a073cce37434ca9cda6917dd8d866b" + SRC_URI = "git://git.infradead.org/mtd-utils.git \ + file://add-exclusion-to-mkfs-jffs2-git-2.patch \ + " + + PV = "1.5.1+git${SRCPV}" + + S = "${WORKDIR}/git" + + EXTRA_OEMAKE = "'CC=${CC}' 'RANLIB=${RANLIB}' 'AR=${AR}' 'CFLAGS=${CFLAGS} -I${S}/include -DWITHOUT_XATTR' 'BUILDDIR=${S}'" + + do_install () { + oe_runmake install DESTDIR=${D} SBINDIR=${sbindir} MANDIR=${mandir} INCLUDEDIR=${includedir} + } + + PACKAGES =+ "mtd-utils-jffs2 mtd-utils-ubifs mtd-utils-misc" + + FILES_mtd-utils-jffs2 = "${sbindir}/mkfs.jffs2 ${sbindir}/jffs2dump ${sbindir}/jffs2reader ${sbindir}/sumtool" + FILES_mtd-utils-ubifs = "${sbindir}/mkfs.ubifs ${sbindir}/ubi*" + FILES_mtd-utils-misc = "${sbindir}/nftl* ${sbindir}/ftl* ${sbindir}/rfd* ${sbindir}/doc* ${sbindir}/serve_image ${sbindir}/recv_image" + + PARALLEL_MAKE = "" + + BBCLASSEXTEND = "native" + +Splitting an Application into Multiple Packages +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You can use the variables ``PACKAGES`` and ``FILES`` to split an +application into multiple packages. + +Following is an example that uses the ``libxpm`` recipe. By default, +this recipe generates a single package that contains the library along +with a few binaries. You can modify the recipe to split the binaries +into separate packages: +:: + + require xorg-lib-common.inc + + SUMMARY = "Xpm: X Pixmap extension library" + LICENSE = "BSD" + LIC_FILES_CHKSUM = "file://COPYING;md5=51f4270b012ecd4ab1a164f5f4ed6cf7" + DEPENDS += "libxext libsm libxt" + PE = "1" + + XORG_PN = "libXpm" + + PACKAGES =+ "sxpm cxpm" + FILES_cxpm = "${bindir}/cxpm" + FILES_sxpm = "${bindir}/sxpm" + +In the previous example, we want to ship the ``sxpm`` and ``cxpm`` +binaries in separate packages. Since ``bindir`` would be packaged into +the main ``PN`` package by default, we prepend the ``PACKAGES`` variable +so additional package names are added to the start of list. This results +in the extra ``FILES_*`` variables then containing information that +define which files and directories go into which packages. Files +included by earlier packages are skipped by latter packages. Thus, the +main ``PN`` package does not include the above listed files. + +Packaging Externally Produced Binaries +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Sometimes, you need to add pre-compiled binaries to an image. For +example, suppose that binaries for proprietary code exist, which are +created by a particular division of a company. Your part of the company +needs to use those binaries as part of an image that you are building +using the OpenEmbedded build system. Since you only have the binaries +and not the source code, you cannot use a typical recipe that expects to +fetch the source specified in +:term:`SRC_URI` and then compile it. + +One method is to package the binaries and then install them as part of +the image. Generally, it is not a good idea to package binaries since, +among other things, it can hinder the ability to reproduce builds and +could lead to compatibility problems with ABI in the future. However, +sometimes you have no choice. + +The easiest solution is to create a recipe that uses the +:ref:`bin_package <ref-classes-bin-package>` class +and to be sure that you are using default locations for build artifacts. +In most cases, the ``bin_package`` class handles "skipping" the +configure and compile steps as well as sets things up to grab packages +from the appropriate area. In particular, this class sets ``noexec`` on +both the :ref:`ref-tasks-configure` +and :ref:`ref-tasks-compile` tasks, +sets ``FILES_${PN}`` to "/" so that it picks up all files, and sets up a +:ref:`ref-tasks-install` task, which +effectively copies all files from ``${S}`` to ``${D}``. The +``bin_package`` class works well when the files extracted into ``${S}`` +are already laid out in the way they should be laid out on the target. +For more information on these variables, see the +:term:`FILES`, +:term:`PN`, +:term:`S`, and +:term:`D` variables in the Yocto Project +Reference Manual's variable glossary. + +.. note:: + + - Using :term:`DEPENDS` is a good + idea even for components distributed in binary form, and is often + necessary for shared libraries. For a shared library, listing the + library dependencies in ``DEPENDS`` makes sure that the libraries + are available in the staging sysroot when other recipes link + against the library, which might be necessary for successful + linking. + + - Using ``DEPENDS`` also allows runtime dependencies between + packages to be added automatically. See the + ":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`" + section in the Yocto Project Overview and Concepts Manual for more + information. + +If you cannot use the ``bin_package`` class, you need to be sure you are +doing the following: + +- Create a recipe where the + :ref:`ref-tasks-configure` and + :ref:`ref-tasks-compile` tasks do + nothing: It is usually sufficient to just not define these tasks in + the recipe, because the default implementations do nothing unless a + Makefile is found in + ``${``\ :term:`S`\ ``}``. + + If ``${S}`` might contain a Makefile, or if you inherit some class + that replaces ``do_configure`` and ``do_compile`` with custom + versions, then you can use the + ``[``\ :ref:`noexec <bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ``]`` + flag to turn the tasks into no-ops, as follows: + :: + + do_configure[noexec] = "1" + do_compile[noexec] = "1" + + Unlike + :ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:deleting a task`, + using the flag preserves the dependency chain from the + :ref:`ref-tasks-fetch`, + :ref:`ref-tasks-unpack`, and + :ref:`ref-tasks-patch` tasks to the + :ref:`ref-tasks-install` task. + +- Make sure your ``do_install`` task installs the binaries + appropriately. + +- Ensure that you set up :term:`FILES` + (usually + ``FILES_${``\ :term:`PN`\ ``}``) to + point to the files you have installed, which of course depends on + where you have installed them and whether those files are in + different locations than the defaults. + +.. note:: + + If image prelinking is enabled (e.g. "image-prelink" is in :term:`USER_CLASSES` + which it is by default), prelink will change the binaries in the generated images + and this often catches people out. Remove that class to ensure binaries are + preserved exactly if that is necessary. + +Following Recipe Style Guidelines +--------------------------------- + +When writing recipes, it is good to conform to existing style +guidelines. The :oe_home:`OpenEmbedded Styleguide </wiki/Styleguide>` wiki page +provides rough guidelines for preferred recipe style. + +It is common for existing recipes to deviate a bit from this style. +However, aiming for at least a consistent style is a good idea. Some +practices, such as omitting spaces around ``=`` operators in assignments +or ordering recipe components in an erratic way, are widely seen as poor +style. + +Recipe Syntax +------------- + +Understanding recipe file syntax is important for writing recipes. The +following list overviews the basic items that make up a BitBake recipe +file. For more complete BitBake syntax descriptions, see the +":doc:`bitbake-user-manual/bitbake-user-manual-metadata`" +chapter of the BitBake User Manual. + +- *Variable Assignments and Manipulations:* Variable assignments allow + a value to be assigned to a variable. The assignment can be static + text or might include the contents of other variables. In addition to + the assignment, appending and prepending operations are also + supported. + + The following example shows some of the ways you can use variables in + recipes: + :: + + S = "${WORKDIR}/postfix-${PV}" + CFLAGS += "-DNO_ASM" + SRC_URI_append = " file://fixup.patch" + +- *Functions:* Functions provide a series of actions to be performed. + You usually use functions to override the default implementation of a + task function or to complement a default function (i.e. append or + prepend to an existing function). Standard functions use ``sh`` shell + syntax, although access to OpenEmbedded variables and internal + methods are also available. + + The following is an example function from the ``sed`` recipe: + :: + + do_install () { + autotools_do_install + install -d ${D}${base_bindir} + mv ${D}${bindir}/sed ${D}${base_bindir}/sed + rmdir ${D}${bindir}/ + } + + It is + also possible to implement new functions that are called between + existing tasks as long as the new functions are not replacing or + complementing the default functions. You can implement functions in + Python instead of shell. Both of these options are not seen in the + majority of recipes. + +- *Keywords:* BitBake recipes use only a few keywords. You use keywords + to include common functions (``inherit``), load parts of a recipe + from other files (``include`` and ``require``) and export variables + to the environment (``export``). + + The following example shows the use of some of these keywords: + :: + + export POSTCONF = "${STAGING_BINDIR}/postconf" + inherit autoconf + require otherfile.inc + +- *Comments (#):* Any lines that begin with the hash character (``#``) + are treated as comment lines and are ignored: + :: + + # This is a comment + +This next list summarizes the most important and most commonly used +parts of the recipe syntax. For more information on these parts of the +syntax, you can reference the +:doc:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata` chapter +in the BitBake User Manual. + +- *Line Continuation (\\):* Use the backward slash (``\``) character to + split a statement over multiple lines. Place the slash character at + the end of the line that is to be continued on the next line: + :: + + VAR = "A really long \ + line" + + .. note:: + + You cannot have any characters including spaces or tabs after the + slash character. + +- *Using Variables (${VARNAME}):* Use the ``${VARNAME}`` syntax to + access the contents of a variable: + :: + + SRC_URI = "${SOURCEFORGE_MIRROR}/libpng/zlib-${PV}.tar.gz" + + .. note:: + + It is important to understand that the value of a variable + expressed in this form does not get substituted automatically. The + expansion of these expressions happens on-demand later (e.g. + usually when a function that makes reference to the variable + executes). This behavior ensures that the values are most + appropriate for the context in which they are finally used. On the + rare occasion that you do need the variable expression to be + expanded immediately, you can use the + := + operator instead of + = + when you make the assignment, but this is not generally needed. + +- *Quote All Assignments ("value"):* Use double quotes around values in + all variable assignments (e.g. ``"value"``). Following is an example: + :: + + VAR1 = "${OTHERVAR}" + VAR2 = "The version is ${PV}" + +- *Conditional Assignment (?=):* Conditional assignment is used to + assign a value to a variable, but only when the variable is currently + unset. Use the question mark followed by the equal sign (``?=``) to + make a "soft" assignment used for conditional assignment. Typically, + "soft" assignments are used in the ``local.conf`` file for variables + that are allowed to come through from the external environment. + + Here is an example where ``VAR1`` is set to "New value" if it is + currently empty. However, if ``VAR1`` has already been set, it + remains unchanged: + :: + + VAR1 ?= "New value" + + In this next example, ``VAR1`` is left with the value "Original value": + :: + + VAR1 = "Original value" + VAR1 ?= "New value" + +- *Appending (+=):* Use the plus character followed by the equals sign + (``+=``) to append values to existing variables. + + .. note:: + + This operator adds a space between the existing content of the + variable and the new content. + + Here is an example: + :: + + SRC_URI += "file://fix-makefile.patch" + +- *Prepending (=+):* Use the equals sign followed by the plus character + (``=+``) to prepend values to existing variables. + + .. note:: + + This operator adds a space between the new content and the + existing content of the variable. + + Here is an example: + :: + + VAR =+ "Starts" + +- *Appending (_append):* Use the ``_append`` operator to append values + to existing variables. This operator does not add any additional + space. Also, the operator is applied after all the ``+=``, and ``=+`` + operators have been applied and after all ``=`` assignments have + occurred. + + The following example shows the space being explicitly added to the + start to ensure the appended value is not merged with the existing + value: + :: + + SRC_URI_append = " file://fix-makefile.patch" + + You can also use + the ``_append`` operator with overrides, which results in the actions + only being performed for the specified target or machine: + :: + + SRC_URI_append_sh4 = " file://fix-makefile.patch" + +- *Prepending (_prepend):* Use the ``_prepend`` operator to prepend + values to existing variables. This operator does not add any + additional space. Also, the operator is applied after all the ``+=``, + and ``=+`` operators have been applied and after all ``=`` + assignments have occurred. + + The following example shows the space being explicitly added to the + end to ensure the prepended value is not merged with the existing + value: + :: + + CFLAGS_prepend = "-I${S}/myincludes " + + You can also use the + ``_prepend`` operator with overrides, which results in the actions + only being performed for the specified target or machine: + :: + + CFLAGS_prepend_sh4 = "-I${S}/myincludes " + +- *Overrides:* You can use overrides to set a value conditionally, + typically based on how the recipe is being built. For example, to set + the :term:`KBRANCH` variable's + value to "standard/base" for any target + :term:`MACHINE`, except for + qemuarm where it should be set to "standard/arm-versatile-926ejs", + you would do the following: + :: + + KBRANCH = "standard/base" + KBRANCH_qemuarm = "standard/arm-versatile-926ejs" + + Overrides are also used to separate + alternate values of a variable in other situations. For example, when + setting variables such as + :term:`FILES` and + :term:`RDEPENDS` that are + specific to individual packages produced by a recipe, you should + always use an override that specifies the name of the package. + +- *Indentation:* Use spaces for indentation rather than tabs. For + shell functions, both currently work. However, it is a policy + decision of the Yocto Project to use tabs in shell functions. Realize + that some layers have a policy to use spaces for all indentation. + +- *Using Python for Complex Operations:* For more advanced processing, + it is possible to use Python code during variable assignments (e.g. + search and replacement on a variable). + + You indicate Python code using the ``${@python_code}`` syntax for the + variable assignment: + :: + + SRC_URI = "ftp://ftp.info-zip.org/pub/infozip/src/zip${@d.getVar('PV',1).replace('.', '')}.tgz + +- *Shell Function Syntax:* Write shell functions as if you were writing + a shell script when you describe a list of actions to take. You + should ensure that your script works with a generic ``sh`` and that + it does not require any ``bash`` or other shell-specific + functionality. The same considerations apply to various system + utilities (e.g. ``sed``, ``grep``, ``awk``, and so forth) that you + might wish to use. If in doubt, you should check with multiple + implementations - including those from BusyBox. + +Adding a New Machine +==================== + +Adding a new machine to the Yocto Project is a straightforward process. +This section describes how to add machines that are similar to those +that the Yocto Project already supports. + +.. note:: + + Although well within the capabilities of the Yocto Project, adding a + totally new architecture might require changes to ``gcc``/``glibc`` + and to the site information, which is beyond the scope of this + manual. + +For a complete example that shows how to add a new machine, see the +":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`" +section in the Yocto Project Board Support Package (BSP) Developer's +Guide. + +Adding the Machine Configuration File +------------------------------------- + +To add a new machine, you need to add a new machine configuration file +to the layer's ``conf/machine`` directory. This configuration file +provides details about the device you are adding. + +The OpenEmbedded build system uses the root name of the machine +configuration file to reference the new machine. For example, given a +machine configuration file named ``crownbay.conf``, the build system +recognizes the machine as "crownbay". + +The most important variables you must set in your machine configuration +file or include from a lower-level configuration file are as follows: + +- ``TARGET_ARCH`` (e.g. "arm") + +- ``PREFERRED_PROVIDER_virtual/kernel`` + +- ``MACHINE_FEATURES`` (e.g. "apm screen wifi") + +You might also need these variables: + +- ``SERIAL_CONSOLES`` (e.g. "115200;ttyS0 115200;ttyS1") + +- ``KERNEL_IMAGETYPE`` (e.g. "zImage") + +- ``IMAGE_FSTYPES`` (e.g. "tar.gz jffs2") + +You can find full details on these variables in the reference section. +You can leverage existing machine ``.conf`` files from +``meta-yocto-bsp/conf/machine/``. + +Adding a Kernel for the Machine +------------------------------- + +The OpenEmbedded build system needs to be able to build a kernel for the +machine. You need to either create a new kernel recipe for this machine, +or extend an existing kernel recipe. You can find several kernel recipe +examples in the Source Directory at ``meta/recipes-kernel/linux`` that +you can use as references. + +If you are creating a new kernel recipe, normal recipe-writing rules +apply for setting up a ``SRC_URI``. Thus, you need to specify any +necessary patches and set ``S`` to point at the source code. You need to +create a ``do_configure`` task that configures the unpacked kernel with +a ``defconfig`` file. You can do this by using a ``make defconfig`` +command or, more commonly, by copying in a suitable ``defconfig`` file +and then running ``make oldconfig``. By making use of ``inherit kernel`` +and potentially some of the ``linux-*.inc`` files, most other +functionality is centralized and the defaults of the class normally work +well. + +If you are extending an existing kernel recipe, it is usually a matter +of adding a suitable ``defconfig`` file. The file needs to be added into +a location similar to ``defconfig`` files used for other machines in a +given kernel recipe. A possible way to do this is by listing the file in +the ``SRC_URI`` and adding the machine to the expression in +``COMPATIBLE_MACHINE``: +:: + + COMPATIBLE_MACHINE = '(qemux86|qemumips)' + +For more information on ``defconfig`` files, see the +":ref:`kernel-dev/kernel-dev-common:changing the configuration`" +section in the Yocto Project Linux Kernel Development Manual. + +Adding a Formfactor Configuration File +-------------------------------------- + +A formfactor configuration file provides information about the target +hardware for which the image is being built and information that the +build system cannot obtain from other sources such as the kernel. Some +examples of information contained in a formfactor configuration file +include framebuffer orientation, whether or not the system has a +keyboard, the positioning of the keyboard in relation to the screen, and +the screen resolution. + +The build system uses reasonable defaults in most cases. However, if +customization is necessary, you need to create a ``machconfig`` file in +the ``meta/recipes-bsp/formfactor/files`` directory. This directory +contains directories for specific machines such as ``qemuarm`` and +``qemux86``. For information about the settings available and the +defaults, see the ``meta/recipes-bsp/formfactor/files/config`` file +found in the same area. + +Following is an example for "qemuarm" machine: +:: + + HAVE_TOUCHSCREEN=1 + HAVE_KEYBOARD=1 + DISPLAY_CAN_ROTATE=0 + DISPLAY_ORIENTATION=0 + #DISPLAY_WIDTH_PIXELS=640 + #DISPLAY_HEIGHT_PIXELS=480 + #DISPLAY_BPP=16 + DISPLAY_DPI=150 + DISPLAY_SUBPIXEL_ORDER=vrgb + +Upgrading Recipes +================= + +Over time, upstream developers publish new versions for software built +by layer recipes. It is recommended to keep recipes up-to-date with +upstream version releases. + +While several methods exist that allow you upgrade a recipe, you might +consider checking on the upgrade status of a recipe first. You can do so +using the ``devtool check-upgrade-status`` command. See the +":ref:`devtool-checking-on-the-upgrade-status-of-a-recipe`" +section in the Yocto Project Reference Manual for more information. + +The remainder of this section describes three ways you can upgrade a +recipe. You can use the Automated Upgrade Helper (AUH) to set up +automatic version upgrades. Alternatively, you can use +``devtool upgrade`` to set up semi-automatic version upgrades. Finally, +you can manually upgrade a recipe by editing the recipe itself. + +Using the Auto Upgrade Helper (AUH) +----------------------------------- + +The AUH utility works in conjunction with the OpenEmbedded build system +in order to automatically generate upgrades for recipes based on new +versions being published upstream. Use AUH when you want to create a +service that performs the upgrades automatically and optionally sends +you an email with the results. + +AUH allows you to update several recipes with a single use. You can also +optionally perform build and integration tests using images with the +results saved to your hard drive and emails of results optionally sent +to recipe maintainers. Finally, AUH creates Git commits with appropriate +commit messages in the layer's tree for the changes made to recipes. + +.. note:: + + Conditions do exist when you should not use AUH to upgrade recipes + and you should instead use either ``devtool upgrade`` or upgrade your + recipes manually: + + - When AUH cannot complete the upgrade sequence. This situation + usually results because custom patches carried by the recipe + cannot be automatically rebased to the new version. In this case, + ``devtool upgrade`` allows you to manually resolve conflicts. + + - When for any reason you want fuller control over the upgrade + process. For example, when you want special arrangements for + testing. + +The following steps describe how to set up the AUH utility: + +1. *Be Sure the Development Host is Set Up:* You need to be sure that + your development host is set up to use the Yocto Project. For + information on how to set up your host, see the + ":ref:`dev-manual/start:Preparing the Build Host`" section. + +2. *Make Sure Git is Configured:* The AUH utility requires Git to be + configured because AUH uses Git to save upgrades. Thus, you must have + Git user and email configured. The following command shows your + configurations: + :: + + $ git config --list + + If you do not have the user and + email configured, you can use the following commands to do so: + :: + + $ git config --global user.name some_name + $ git config --global user.email username@domain.com + +3. *Clone the AUH Repository:* To use AUH, you must clone the repository + onto your development host. The following command uses Git to create + a local copy of the repository on your system: + :: + + $ git clone git://git.yoctoproject.org/auto-upgrade-helper + Cloning into 'auto-upgrade-helper'... remote: Counting objects: 768, done. + remote: Compressing objects: 100% (300/300), done. + remote: Total 768 (delta 499), reused 703 (delta 434) + Receiving objects: 100% (768/768), 191.47 KiB | 98.00 KiB/s, done. + Resolving deltas: 100% (499/499), done. + Checking connectivity... done. + + AUH is not part of the :term:`OpenEmbedded-Core (OE-Core)` or + :term:`Poky` repositories. + +4. *Create a Dedicated Build Directory:* Run the + :ref:`structure-core-script` + script to create a fresh build directory that you use exclusively for + running the AUH utility: + :: + + $ cd ~/poky + $ source oe-init-build-env your_AUH_build_directory + + Re-using an existing build directory and its configurations is not + recommended as existing settings could cause AUH to fail or behave + undesirably. + +5. *Make Configurations in Your Local Configuration File:* Several + settings need to exist in the ``local.conf`` file in the build + directory you just created for AUH. Make these following + configurations: + + - If you want to enable :ref:`Build + History <dev-manual/common-tasks:maintaining build output quality>`, + which is optional, you need the following lines in the + ``conf/local.conf`` file: + :: + + INHERIT =+ "buildhistory" + BUILDHISTORY_COMMIT = "1" + + With this configuration and a successful + upgrade, a build history "diff" file appears in the + ``upgrade-helper/work/recipe/buildhistory-diff.txt`` file found in + your build directory. + + - If you want to enable testing through the + :ref:`testimage <ref-classes-testimage*>` + class, which is optional, you need to have the following set in + your ``conf/local.conf`` file: + :: + + INHERIT += "testimage" + + .. note:: + + If your distro does not enable by default ptest, which Poky + does, you need the following in your ``local.conf`` file: + :: + + DISTRO_FEATURES_append = " ptest" + + +6. *Optionally Start a vncserver:* If you are running in a server + without an X11 session, you need to start a vncserver: + :: + + $ vncserver :1 + $ export DISPLAY=:1 + +7. *Create and Edit an AUH Configuration File:* You need to have the + ``upgrade-helper/upgrade-helper.conf`` configuration file in your + build directory. You can find a sample configuration file in the + :yocto_git:`AUH source repository </auto-upgrade-helper/tree/>`. + + Read through the sample file and make configurations as needed. For + example, if you enabled build history in your ``local.conf`` as + described earlier, you must enable it in ``upgrade-helper.conf``. + + Also, if you are using the default ``maintainers.inc`` file supplied + with Poky and located in ``meta-yocto`` and you do not set a + "maintainers_whitelist" or "global_maintainer_override" in the + ``upgrade-helper.conf`` configuration, and you specify "-e all" on + the AUH command-line, the utility automatically sends out emails to + all the default maintainers. Please avoid this. + +This next set of examples describes how to use the AUH: + +- *Upgrading a Specific Recipe:* To upgrade a specific recipe, use the + following form: + :: + + $ upgrade-helper.py recipe_name + + For example, this command upgrades the ``xmodmap`` recipe: + :: + + $ upgrade-helper.py xmodmap + +- *Upgrading a Specific Recipe to a Particular Version:* To upgrade a + specific recipe to a particular version, use the following form: + :: + + $ upgrade-helper.py recipe_name -t version + + For example, this command upgrades the ``xmodmap`` recipe to version 1.2.3: + :: + + $ upgrade-helper.py xmodmap -t 1.2.3 + +- *Upgrading all Recipes to the Latest Versions and Suppressing Email + Notifications:* To upgrade all recipes to their most recent versions + and suppress the email notifications, use the following command: + :: + + $ upgrade-helper.py all + +- *Upgrading all Recipes to the Latest Versions and Send Email + Notifications:* To upgrade all recipes to their most recent versions + and send email messages to maintainers for each attempted recipe as + well as a status email, use the following command: + :: + + $ upgrade-helper.py -e all + +Once you have run the AUH utility, you can find the results in the AUH +build directory: +:: + + ${BUILDDIR}/upgrade-helper/timestamp + +The AUH utility +also creates recipe update commits from successful upgrade attempts in +the layer tree. + +You can easily set up to run the AUH utility on a regular basis by using +a cron job. See the +:yocto_git:`weeklyjob.sh </auto-upgrade-helper/tree/weeklyjob.sh>` +file distributed with the utility for an example. + +Using ``devtool upgrade`` +------------------------- + +As mentioned earlier, an alternative method for upgrading recipes to +newer versions is to use +:doc:`devtool upgrade </ref-manual/ref-devtool-reference>`. +You can read about ``devtool upgrade`` in general in the +":ref:`sdk-manual/sdk-extensible:use \`\`devtool upgrade\`\` to create a version of the recipe that supports a newer version of the software`" +section in the Yocto Project Application Development and the Extensible +Software Development Kit (eSDK) Manual. + +To see all the command-line options available with ``devtool upgrade``, +use the following help command: +:: + + $ devtool upgrade -h + +If you want to find out what version a recipe is currently at upstream +without any attempt to upgrade your local version of the recipe, you can +use the following command: +:: + + $ devtool latest-version recipe_name + +As mentioned in the previous section describing AUH, ``devtool upgrade`` +works in a less-automated manner than AUH. Specifically, +``devtool upgrade`` only works on a single recipe that you name on the +command line, cannot perform build and integration testing using images, +and does not automatically generate commits for changes in the source +tree. Despite all these "limitations", ``devtool upgrade`` updates the +recipe file to the new upstream version and attempts to rebase custom +patches contained by the recipe as needed. + +.. note:: + + AUH uses much of ``devtool upgrade`` behind the scenes making AUH somewhat + of a "wrapper" application for ``devtool upgrade``. + +A typical scenario involves having used Git to clone an upstream +repository that you use during build operations. Because you have built the +recipe in the past, the layer is likely added to your +configuration already. If for some reason, the layer is not added, you +could add it easily using the +":ref:`bitbake-layers <bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script>`" +script. For example, suppose you use the ``nano.bb`` recipe from the +``meta-oe`` layer in the ``meta-openembedded`` repository. For this +example, assume that the layer has been cloned into following area: +:: + + /home/scottrif/meta-openembedded + +The following command from your +:term:`Build Directory` adds the layer to +your build configuration (i.e. ``${BUILDDIR}/conf/bblayers.conf``): +:: + + $ bitbake-layers add-layer /home/scottrif/meta-openembedded/meta-oe + NOTE: Starting bitbake server... + Parsing recipes: 100% |##########################################| Time: 0:00:55 + Parsing of 1431 .bb files complete (0 cached, 1431 parsed). 2040 targets, 56 skipped, 0 masked, 0 errors. + Removing 12 recipes from the x86_64 sysroot: 100% |##############| Time: 0:00:00 + Removing 1 recipes from the x86_64_i586 sysroot: 100% |##########| Time: 0:00:00 + Removing 5 recipes from the i586 sysroot: 100% |#################| Time: 0:00:00 + Removing 5 recipes from the qemux86 sysroot: 100% |##############| Time: 0:00:00 + +For this example, assume that the ``nano.bb`` recipe that +is upstream has a 2.9.3 version number. However, the version in the +local repository is 2.7.4. The following command from your build +directory automatically upgrades the recipe for you: + +.. note:: + + Using the ``-V`` option is not necessary. Omitting the version number causes + ``devtool upgrade`` to upgrade the recipe to the most recent version. + +:: + + $ devtool upgrade nano -V 2.9.3 + NOTE: Starting bitbake server... + NOTE: Creating workspace layer in /home/scottrif/poky/build/workspace + Parsing recipes: 100% |##########################################| Time: 0:00:46 + Parsing of 1431 .bb files complete (0 cached, 1431 parsed). 2040 targets, 56 skipped, 0 masked, 0 errors. + NOTE: Extracting current version source... + NOTE: Resolving any missing task queue dependencies + . + . + . + NOTE: Executing SetScene Tasks + NOTE: Executing RunQueue Tasks + NOTE: Tasks Summary: Attempted 74 tasks of which 72 didn't need to be rerun and all succeeded. + Adding changed files: 100% |#####################################| Time: 0:00:00 + NOTE: Upgraded source extracted to /home/scottrif/poky/build/workspace/sources/nano + NOTE: New recipe is /home/scottrif/poky/build/workspace/recipes/nano/nano_2.9.3.bb + +Continuing with this example, you can use ``devtool build`` to build the +newly upgraded recipe: +:: + + $ devtool build nano + NOTE: Starting bitbake server... + Loading cache: 100% |################################################################################################| Time: 0:00:01 + Loaded 2040 entries from dependency cache. + Parsing recipes: 100% |##############################################################################################| Time: 0:00:00 + Parsing of 1432 .bb files complete (1431 cached, 1 parsed). 2041 targets, 56 skipped, 0 masked, 0 errors. + NOTE: Resolving any missing task queue dependencies + . + . + . + NOTE: Executing SetScene Tasks + NOTE: Executing RunQueue Tasks + NOTE: nano: compiling from external source tree /home/scottrif/poky/build/workspace/sources/nano + NOTE: Tasks Summary: Attempted 520 tasks of which 304 didn't need to be rerun and all succeeded. + +Within the ``devtool upgrade`` workflow, opportunity +exists to deploy and test your rebuilt software. For this example, +however, running ``devtool finish`` cleans up the workspace once the +source in your workspace is clean. This usually means using Git to stage +and submit commits for the changes generated by the upgrade process. + +Once the tree is clean, you can clean things up in this example with the +following command from the ``${BUILDDIR}/workspace/sources/nano`` +directory: +:: + + $ devtool finish nano meta-oe + NOTE: Starting bitbake server... + Loading cache: 100% |################################################################################################| Time: 0:00:00 + Loaded 2040 entries from dependency cache. + Parsing recipes: 100% |##############################################################################################| Time: 0:00:01 + Parsing of 1432 .bb files complete (1431 cached, 1 parsed). 2041 targets, 56 skipped, 0 masked, 0 errors. + NOTE: Adding new patch 0001-nano.bb-Stuff-I-changed-when-upgrading-nano.bb.patch + NOTE: Updating recipe nano_2.9.3.bb + NOTE: Removing file /home/scottrif/meta-openembedded/meta-oe/recipes-support/nano/nano_2.7.4.bb + NOTE: Moving recipe file to /home/scottrif/meta-openembedded/meta-oe/recipes-support/nano + NOTE: Leaving source tree /home/scottrif/poky/build/workspace/sources/nano as-is; if you no longer need it then please delete it manually + + +Using the ``devtool finish`` command cleans up the workspace and creates a patch +file based on your commits. The tool puts all patch files back into the +source directory in a sub-directory named ``nano`` in this case. + +Manually Upgrading a Recipe +--------------------------- + +If for some reason you choose not to upgrade recipes using +:ref:`dev-manual/common-tasks:Using the Auto Upgrade Helper (AUH)` or +by :ref:`dev-manual/common-tasks:Using \`\`devtool upgrade\`\``, +you can manually edit the recipe files to upgrade the versions. + +.. note:: + + Manually updating multiple recipes scales poorly and involves many + steps. The recommendation to upgrade recipe versions is through AUH + or ``devtool upgrade``, both of which automate some steps and provide + guidance for others needed for the manual process. + +To manually upgrade recipe versions, follow these general steps: + +1. *Change the Version:* Rename the recipe such that the version (i.e. + the :term:`PV` part of the recipe name) + changes appropriately. If the version is not part of the recipe name, + change the value as it is set for ``PV`` within the recipe itself. + +2. *Update* ``SRCREV`` *if Needed*: If the source code your recipe builds + is fetched from Git or some other version control system, update + :term:`SRCREV` to point to the + commit hash that matches the new version. + +3. *Build the Software:* Try to build the recipe using BitBake. Typical + build failures include the following: + + - License statements were updated for the new version. For this + case, you need to review any changes to the license and update the + values of :term:`LICENSE` and + :term:`LIC_FILES_CHKSUM` + as needed. + + .. note:: + + License changes are often inconsequential. For example, the + license text's copyright year might have changed. + + - Custom patches carried by the older version of the recipe might + fail to apply to the new version. For these cases, you need to + review the failures. Patches might not be necessary for the new + version of the software if the upgraded version has fixed those + issues. If a patch is necessary and failing, you need to rebase it + into the new version. + +4. *Optionally Attempt to Build for Several Architectures:* Once you + successfully build the new software for a given architecture, you + could test the build for other architectures by changing the + :term:`MACHINE` variable and + rebuilding the software. This optional step is especially important + if the recipe is to be released publicly. + +5. *Check the Upstream Change Log or Release Notes:* Checking both these + reveals if new features exist that could break + backwards-compatibility. If so, you need to take steps to mitigate or + eliminate that situation. + +6. *Optionally Create a Bootable Image and Test:* If you want, you can + test the new software by booting it onto actual hardware. + +7. *Create a Commit with the Change in the Layer Repository:* After all + builds work and any testing is successful, you can create commits for + any changes in the layer holding your upgraded recipe. + +Finding Temporary Source Code +============================= + +You might find it helpful during development to modify the temporary +source code used by recipes to build packages. For example, suppose you +are developing a patch and you need to experiment a bit to figure out +your solution. After you have initially built the package, you can +iteratively tweak the source code, which is located in the +:term:`Build Directory`, and then you can +force a re-compile and quickly test your altered code. Once you settle +on a solution, you can then preserve your changes in the form of +patches. + +During a build, the unpacked temporary source code used by recipes to +build packages is available in the Build Directory as defined by the +:term:`S` variable. Below is the default +value for the ``S`` variable as defined in the +``meta/conf/bitbake.conf`` configuration file in the +:term:`Source Directory`: +:: + + S = "${WORKDIR}/${BP}" + +You should be aware that many recipes override the +``S`` variable. For example, recipes that fetch their source from Git +usually set ``S`` to ``${WORKDIR}/git``. + +.. note:: + + The :term:`BP` represents the base recipe name, which consists of the name + and version: + :: + + BP = "${BPN}-${PV}" + + +The path to the work directory for the recipe +(:term:`WORKDIR`) is defined as +follows: +:: + + ${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR} + +The actual directory depends on several things: + +- :term:`TMPDIR`: The top-level build + output directory. + +- :term:`MULTIMACH_TARGET_SYS`: + The target system identifier. + +- :term:`PN`: The recipe name. + +- :term:`EXTENDPE`: The epoch - (if + :term:`PE` is not specified, which is + usually the case for most recipes, then ``EXTENDPE`` is blank). + +- :term:`PV`: The recipe version. + +- :term:`PR`: The recipe revision. + +As an example, assume a Source Directory top-level folder named +``poky``, a default Build Directory at ``poky/build``, and a +``qemux86-poky-linux`` machine target system. Furthermore, suppose your +recipe is named ``foo_1.3.0.bb``. In this case, the work directory the +build system uses to build the package would be as follows: +:: + + poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0 + +Using Quilt in Your Workflow +============================ + +`Quilt <https://savannah.nongnu.org/projects/quilt>`__ is a powerful tool +that allows you to capture source code changes without having a clean +source tree. This section outlines the typical workflow you can use to +modify source code, test changes, and then preserve the changes in the +form of a patch all using Quilt. + +.. note:: + + With regard to preserving changes to source files, if you clean a + recipe or have ``rm_work`` enabled, the + :ref:`devtool workflow <sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow>` + as described in the Yocto Project Application Development and the + Extensible Software Development Kit (eSDK) manual is a safer + development flow than the flow that uses Quilt. + +Follow these general steps: + +1. *Find the Source Code:* Temporary source code used by the + OpenEmbedded build system is kept in the + :term:`Build Directory`. See the + "`Finding Temporary Source + Code <#finding-the-temporary-source-code>`__" section to learn how to + locate the directory that has the temporary source code for a + particular package. + +2. *Change Your Working Directory:* You need to be in the directory that + has the temporary source code. That directory is defined by the + :term:`S` variable. + +3. *Create a New Patch:* Before modifying source code, you need to + create a new patch. To create a new patch file, use ``quilt new`` as + below: + :: + + $ quilt new my_changes.patch + +4. *Notify Quilt and Add Files:* After creating the patch, you need to + notify Quilt about the files you plan to edit. You notify Quilt by + adding the files to the patch you just created: + :: + + $ quilt add file1.c file2.c file3.c + +5. *Edit the Files:* Make your changes in the source code to the files + you added to the patch. + +6. *Test Your Changes:* Once you have modified the source code, the + easiest way to test your changes is by calling the ``do_compile`` + task as shown in the following example: + :: + + $ bitbake -c compile -f package + + The ``-f`` or ``--force`` option forces the specified task to + execute. If you find problems with your code, you can just keep + editing and re-testing iteratively until things work as expected. + + .. note:: + + All the modifications you make to the temporary source code disappear + once you run the ``do_clean`` or ``do_cleanall`` tasks using BitBake + (i.e. ``bitbake -c clean package`` and ``bitbake -c cleanall package``). + Modifications will also disappear if you use the ``rm_work`` feature as + described in the + ":ref:`dev-manual/common-tasks:conserving disk space during builds`" + section. + +7. *Generate the Patch:* Once your changes work as expected, you need to + use Quilt to generate the final patch that contains all your + modifications. + :: + + $ quilt refresh + + At this point, the + ``my_changes.patch`` file has all your edits made to the ``file1.c``, + ``file2.c``, and ``file3.c`` files. + + You can find the resulting patch file in the ``patches/`` + subdirectory of the source (``S``) directory. + +8. *Copy the Patch File:* For simplicity, copy the patch file into a + directory named ``files``, which you can create in the same directory + that holds the recipe (``.bb``) file or the append (``.bbappend``) + file. Placing the patch here guarantees that the OpenEmbedded build + system will find the patch. Next, add the patch into the ``SRC_URI`` + of the recipe. Here is an example: + :: + + SRC_URI += "file://my_changes.patch" + +Using a Development Shell +========================= + +When debugging certain commands or even when just editing packages, +``devshell`` can be a useful tool. When you invoke ``devshell``, all +tasks up to and including +:ref:`ref-tasks-patch` are run for the +specified target. Then, a new terminal is opened and you are placed in +``${``\ :term:`S`\ ``}``, the source +directory. In the new terminal, all the OpenEmbedded build-related +environment variables are still defined so you can use commands such as +``configure`` and ``make``. The commands execute just as if the +OpenEmbedded build system were executing them. Consequently, working +this way can be helpful when debugging a build or preparing software to +be used with the OpenEmbedded build system. + +Following is an example that uses ``devshell`` on a target named +``matchbox-desktop``: +:: + + $ bitbake matchbox-desktop -c devshell + +This command spawns a terminal with a shell prompt within the +OpenEmbedded build environment. The +:term:`OE_TERMINAL` variable +controls what type of shell is opened. + +For spawned terminals, the following occurs: + +- The ``PATH`` variable includes the cross-toolchain. + +- The ``pkgconfig`` variables find the correct ``.pc`` files. + +- The ``configure`` command finds the Yocto Project site files as well + as any other necessary files. + +Within this environment, you can run configure or compile commands as if +they were being run by the OpenEmbedded build system itself. As noted +earlier, the working directory also automatically changes to the Source +Directory (:term:`S`). + +To manually run a specific task using ``devshell``, run the +corresponding ``run.*`` script in the +``${``\ :term:`WORKDIR`\ ``}/temp`` +directory (e.g., ``run.do_configure.``\ `pid`). If a task's script does +not exist, which would be the case if the task was skipped by way of the +sstate cache, you can create the task by first running it outside of the +``devshell``: +:: + + $ bitbake -c task + +.. note:: + + - Execution of a task's ``run.*`` script and BitBake's execution of + a task are identical. In other words, running the script re-runs + the task just as it would be run using the ``bitbake -c`` command. + + - Any ``run.*`` file that does not have a ``.pid`` extension is a + symbolic link (symlink) to the most recent version of that file. + +Remember, that the ``devshell`` is a mechanism that allows you to get +into the BitBake task execution environment. And as such, all commands +must be called just as BitBake would call them. That means you need to +provide the appropriate options for cross-compilation and so forth as +applicable. + +When you are finished using ``devshell``, exit the shell or close the +terminal window. + +.. note:: + + - It is worth remembering that when using ``devshell`` you need to + use the full compiler name such as ``arm-poky-linux-gnueabi-gcc`` + instead of just using ``gcc``. The same applies to other + applications such as ``binutils``, ``libtool`` and so forth. + BitBake sets up environment variables such as ``CC`` to assist + applications, such as ``make`` to find the correct tools. + + - It is also worth noting that ``devshell`` still works over X11 + forwarding and similar situations. + +Using a Development Python Shell +================================ + +Similar to working within a development shell as described in the +previous section, you can also spawn and work within an interactive +Python development shell. When debugging certain commands or even when +just editing packages, ``devpyshell`` can be a useful tool. When you +invoke ``devpyshell``, all tasks up to and including +:ref:`ref-tasks-patch` are run for the +specified target. Then a new terminal is opened. Additionally, key +Python objects and code are available in the same way they are to +BitBake tasks, in particular, the data store 'd'. So, commands such as +the following are useful when exploring the data store and running +functions: +:: + + pydevshell> d.getVar("STAGING_DIR") + '/media/build1/poky/build/tmp/sysroots' + pydevshell> d.getVar("STAGING_DIR") + '${TMPDIR}/sysroots' + pydevshell> d.setVar("FOO", "bar") + pydevshell> d.getVar("FOO") + 'bar' + pydevshell> d.delVar("FOO") + pydevshell> d.getVar("FOO") + pydevshell> bb.build.exec_func("do_unpack", d) + pydevshell> + +The commands execute just as if the OpenEmbedded build +system were executing them. Consequently, working this way can be +helpful when debugging a build or preparing software to be used with the +OpenEmbedded build system. + +Following is an example that uses ``devpyshell`` on a target named +``matchbox-desktop``: +:: + + $ bitbake matchbox-desktop -c devpyshell + +This command spawns a terminal and places you in an interactive Python +interpreter within the OpenEmbedded build environment. The +:term:`OE_TERMINAL` variable +controls what type of shell is opened. + +When you are finished using ``devpyshell``, you can exit the shell +either by using Ctrl+d or closing the terminal window. + +Building +======== + +This section describes various build procedures. For example, the steps +needed for a simple build, a target that uses multiple configurations, +building an image for more than one machine, and so forth. + +Building a Simple Image +----------------------- + +In the development environment, you need to build an image whenever you +change hardware support, add or change system libraries, or add or +change services that have dependencies. Several methods exist that allow +you to build an image within the Yocto Project. This section presents +the basic steps you need to build a simple image using BitBake from a +build host running Linux. + +.. note:: + + - For information on how to build an image using + :term:`Toaster`, see the + :doc:`/toaster-manual/index`. + + - For information on how to use ``devtool`` to build images, see the + ":ref:`sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow`" + section in the Yocto Project Application Development and the + Extensible Software Development Kit (eSDK) manual. + + - For a quick example on how to build an image using the + OpenEmbedded build system, see the + :doc:`/brief-yoctoprojectqs/index` document. + +The build process creates an entire Linux distribution from source and +places it in your :term:`Build Directory` under +``tmp/deploy/images``. For detailed information on the build process +using BitBake, see the ":ref:`overview-manual/overview-manual-concepts:images`" section in the +Yocto Project Overview and Concepts Manual. + +The following figure and list overviews the build process: + +.. image:: figures/bitbake-build-flow.png + :align: center + +1. *Set up Your Host Development System to Support Development Using the + Yocto Project*: See the ":doc:`start`" section for options on how to get a + build host ready to use the Yocto Project. + +2. *Initialize the Build Environment:* Initialize the build environment + by sourcing the build environment script (i.e. + :ref:`structure-core-script`): + :: + + $ source oe-init-build-env [build_dir] + + When you use the initialization script, the OpenEmbedded build system + uses ``build`` as the default :term:`Build Directory` in your current work + directory. You can use a `build_dir` argument with the script to + specify a different build directory. + + .. note:: + + A common practice is to use a different Build Directory for + different targets. For example, ``~/build/x86`` for a ``qemux86`` + target, and ``~/build/arm`` for a ``qemuarm`` target. + +3. *Make Sure Your* ``local.conf`` *File is Correct*: Ensure the + ``conf/local.conf`` configuration file, which is found in the Build + Directory, is set up how you want it. This file defines many aspects + of the build environment including the target machine architecture + through the ``MACHINE`` variable, the packaging format used during + the build + (:term:`PACKAGE_CLASSES`), + and a centralized tarball download directory through the + :term:`DL_DIR` variable. + +4. *Build the Image:* Build the image using the ``bitbake`` command: + :: + + $ bitbake target + + .. note:: + + For information on BitBake, see the :doc:`bitbake:index`. + + The target is the name of the recipe you want to build. Common + targets are the images in ``meta/recipes-core/images``, + ``meta/recipes-sato/images``, and so forth all found in the + :term:`Source Directory`. Or, the target + can be the name of a recipe for a specific piece of software such as + BusyBox. For more details about the images the OpenEmbedded build + system supports, see the + ":ref:`ref-manual/ref-images:Images`" chapter in the Yocto + Project Reference Manual. + + As an example, the following command builds the + ``core-image-minimal`` image: + :: + + $ bitbake core-image-minimal + + Once an + image has been built, it often needs to be installed. The images and + kernels built by the OpenEmbedded build system are placed in the + Build Directory in ``tmp/deploy/images``. For information on how to + run pre-built images such as ``qemux86`` and ``qemuarm``, see the + :doc:`/sdk-manual/index` manual. For + information about how to install these images, see the documentation + for your particular board or machine. + +Building Images for Multiple Targets Using Multiple Configurations +------------------------------------------------------------------ + +You can use a single ``bitbake`` command to build multiple images or +packages for different targets where each image or package requires a +different configuration (multiple configuration builds). The builds, in +this scenario, are sometimes referred to as "multiconfigs", and this +section uses that term throughout. + +This section describes how to set up for multiple configuration builds +and how to account for cross-build dependencies between the +multiconfigs. + +Setting Up and Running a Multiple Configuration Build +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To accomplish a multiple configuration build, you must define each +target's configuration separately using a parallel configuration file in +the :term:`Build Directory`, and you +must follow a required file hierarchy. Additionally, you must enable the +multiple configuration builds in your ``local.conf`` file. + +Follow these steps to set up and execute multiple configuration builds: + +- *Create Separate Configuration Files*: You need to create a single + configuration file for each build target (each multiconfig). + Minimally, each configuration file must define the machine and the + temporary directory BitBake uses for the build. Suggested practice + dictates that you do not overlap the temporary directories used + during the builds. However, it is possible that you can share the + temporary directory + (:term:`TMPDIR`). For example, + consider a scenario with two different multiconfigs for the same + :term:`MACHINE`: "qemux86" built + for two distributions such as "poky" and "poky-lsb". In this case, + you might want to use the same ``TMPDIR``. + + Here is an example showing the minimal statements needed in a + configuration file for a "qemux86" target whose temporary build + directory is ``tmpmultix86``: + :: + + MACHINE = "qemux86" + TMPDIR = "${TOPDIR}/tmpmultix86" + + The location for these multiconfig configuration files is specific. + They must reside in the current build directory in a sub-directory of + ``conf`` named ``multiconfig``. Following is an example that defines + two configuration files for the "x86" and "arm" multiconfigs: + + .. image:: figures/multiconfig_files.png + :align: center + + The reason for this required file hierarchy is because the ``BBPATH`` + variable is not constructed until the layers are parsed. + Consequently, using the configuration file as a pre-configuration + file is not possible unless it is located in the current working + directory. + +- *Add the BitBake Multi-configuration Variable to the Local + Configuration File*: Use the + :term:`BBMULTICONFIG` + variable in your ``conf/local.conf`` configuration file to specify + each multiconfig. Continuing with the example from the previous + figure, the ``BBMULTICONFIG`` variable needs to enable two + multiconfigs: "x86" and "arm" by specifying each configuration file: + :: + + BBMULTICONFIG = "x86 arm" + + .. note:: + + A "default" configuration already exists by definition. This + configuration is named: "" (i.e. empty string) and is defined by + the variables coming from your ``local.conf`` + file. Consequently, the previous example actually adds two + additional configurations to your build: "arm" and "x86" along + with "". + +- *Launch BitBake*: Use the following BitBake command form to launch + the multiple configuration build: + :: + + $ bitbake [mc:multiconfigname:]target [[[mc:multiconfigname:]target] ... ] + + For the example in this section, the following command applies: + :: + + $ bitbake mc:x86:core-image-minimal mc:arm:core-image-sato mc::core-image-base + + The previous BitBake command builds a ``core-image-minimal`` image + that is configured through the ``x86.conf`` configuration file, a + ``core-image-sato`` image that is configured through the ``arm.conf`` + configuration file and a ``core-image-base`` that is configured + through your ``local.conf`` configuration file. + +.. note:: + + Support for multiple configuration builds in the Yocto Project &DISTRO; + (&DISTRO_NAME;) Release does not include Shared State (sstate) + optimizations. Consequently, if a build uses the same object twice + in, for example, two different ``TMPDIR`` + directories, the build either loads from an existing sstate cache for + that build at the start or builds the object fresh. + +Enabling Multiple Configuration Build Dependencies +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Sometimes dependencies can exist between targets (multiconfigs) in a +multiple configuration build. For example, suppose that in order to +build a ``core-image-sato`` image for an "x86" multiconfig, the root +filesystem of an "arm" multiconfig must exist. This dependency is +essentially that the +:ref:`ref-tasks-image` task in the +``core-image-sato`` recipe depends on the completion of the +:ref:`ref-tasks-rootfs` task of the +``core-image-minimal`` recipe. + +To enable dependencies in a multiple configuration build, you must +declare the dependencies in the recipe using the following statement +form: +:: + + task_or_package[mcdepends] = "mc:from_multiconfig:to_multiconfig:recipe_name:task_on_which_to_depend" + +To better show how to use this statement, consider the example scenario +from the first paragraph of this section. The following statement needs +to be added to the recipe that builds the ``core-image-sato`` image: +:: + + do_image[mcdepends] = "mc:x86:arm:core-image-minimal:do_rootfs" + +In this example, the `from_multiconfig` is "x86". The `to_multiconfig` is "arm". The +task on which the ``do_image`` task in the recipe depends is the +``do_rootfs`` task from the ``core-image-minimal`` recipe associated +with the "arm" multiconfig. + +Once you set up this dependency, you can build the "x86" multiconfig +using a BitBake command as follows: +:: + + $ bitbake mc:x86:core-image-sato + +This command executes all the tasks needed to create the +``core-image-sato`` image for the "x86" multiconfig. Because of the +dependency, BitBake also executes through the ``do_rootfs`` task for the +"arm" multiconfig build. + +Having a recipe depend on the root filesystem of another build might not +seem that useful. Consider this change to the statement in the +``core-image-sato`` recipe: +:: + + do_image[mcdepends] = "mc:x86:arm:core-image-minimal:do_image" + +In this case, BitBake must +create the ``core-image-minimal`` image for the "arm" build since the +"x86" build depends on it. + +Because "x86" and "arm" are enabled for multiple configuration builds +and have separate configuration files, BitBake places the artifacts for +each build in the respective temporary build directories (i.e. +:term:`TMPDIR`). + +Building an Initial RAM Filesystem (initramfs) Image +---------------------------------------------------- + +An initial RAM filesystem (initramfs) image provides a temporary root +filesystem used for early system initialization (e.g. loading of modules +needed to locate and mount the "real" root filesystem). + +.. note:: + + The initramfs image is the successor of initial RAM disk (initrd). It + is a "copy in and out" (cpio) archive of the initial filesystem that + gets loaded into memory during the Linux startup process. Because + Linux uses the contents of the archive during initialization, the + initramfs image needs to contain all of the device drivers and tools + needed to mount the final root filesystem. + +Follow these steps to create an initramfs image: + +1. *Create the initramfs Image Recipe:* You can reference the + ``core-image-minimal-initramfs.bb`` recipe found in the + ``meta/recipes-core`` directory of the :term:`Source Directory` + as an example + from which to work. + +2. *Decide if You Need to Bundle the initramfs Image Into the Kernel + Image:* If you want the initramfs image that is built to be bundled + in with the kernel image, set the + :term:`INITRAMFS_IMAGE_BUNDLE` + variable to "1" in your ``local.conf`` configuration file and set the + :term:`INITRAMFS_IMAGE` + variable in the recipe that builds the kernel image. + + .. note:: + + It is recommended that you do bundle the initramfs image with the + kernel image to avoid circular dependencies between the kernel + recipe and the initramfs recipe should the initramfs image include + kernel modules. + + Setting the ``INITRAMFS_IMAGE_BUNDLE`` flag causes the initramfs + image to be unpacked into the ``${B}/usr/`` directory. The unpacked + initramfs image is then passed to the kernel's ``Makefile`` using the + :term:`CONFIG_INITRAMFS_SOURCE` + variable, allowing the initramfs image to be built into the kernel + normally. + + .. note:: + + If you choose to not bundle the initramfs image with the kernel + image, you are essentially using an + `Initial RAM Disk (initrd) <https://en.wikipedia.org/wiki/Initrd>`__. + Creating an initrd is handled primarily through the :term:`INITRD_IMAGE`, + ``INITRD_LIVE``, and ``INITRD_IMAGE_LIVE`` variables. For more + information, see the :ref:`ref-classes-image-live` file. + +3. *Optionally Add Items to the initramfs Image Through the initramfs + Image Recipe:* If you add items to the initramfs image by way of its + recipe, you should use + :term:`PACKAGE_INSTALL` + rather than + :term:`IMAGE_INSTALL`. + ``PACKAGE_INSTALL`` gives more direct control of what is added to the + image as compared to the defaults you might not necessarily want that + are set by the :ref:`image <ref-classes-image>` + or :ref:`core-image <ref-classes-core-image>` + classes. + +4. *Build the Kernel Image and the initramfs Image:* Build your kernel + image using BitBake. Because the initramfs image recipe is a + dependency of the kernel image, the initramfs image is built as well + and bundled with the kernel image if you used the + :term:`INITRAMFS_IMAGE_BUNDLE` + variable described earlier. + +Building a Tiny System +---------------------- + +Very small distributions have some significant advantages such as +requiring less on-die or in-package memory (cheaper), better performance +through efficient cache usage, lower power requirements due to less +memory, faster boot times, and reduced development overhead. Some +real-world examples where a very small distribution gives you distinct +advantages are digital cameras, medical devices, and small headless +systems. + +This section presents information that shows you how you can trim your +distribution to even smaller sizes than the ``poky-tiny`` distribution, +which is around 5 Mbytes, that can be built out-of-the-box using the +Yocto Project. + +Tiny System Overview +~~~~~~~~~~~~~~~~~~~~ + +The following list presents the overall steps you need to consider and +perform to create distributions with smaller root filesystems, achieve +faster boot times, maintain your critical functionality, and avoid +initial RAM disks: + +- `Determine your goals and guiding + principles. <#goals-and-guiding-principles>`__ + +- `Understand what contributes to your image + size. <#understand-what-gives-your-image-size>`__ + +- `Reduce the size of the root + filesystem. <#trim-the-root-filesystem>`__ + +- `Reduce the size of the kernel. <#trim-the-kernel>`__ + +- `Eliminate packaging + requirements. <#remove-package-management-requirements>`__ + +- `Look for other ways to minimize + size. <#look-for-other-ways-to-minimize-size>`__ + +- `Iterate on the process. <#iterate-on-the-process>`__ + +Goals and Guiding Principles +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Before you can reach your destination, you need to know where you are +going. Here is an example list that you can use as a guide when creating +very small distributions: + +- Determine how much space you need (e.g. a kernel that is 1 Mbyte or + less and a root filesystem that is 3 Mbytes or less). + +- Find the areas that are currently taking 90% of the space and + concentrate on reducing those areas. + +- Do not create any difficult "hacks" to achieve your goals. + +- Leverage the device-specific options. + +- Work in a separate layer so that you keep changes isolated. For + information on how to create layers, see the "`Understanding and + Creating Layers <#understanding-and-creating-layers>`__" section. + +Understand What Contributes to Your Image Size +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It is easiest to have something to start with when creating your own +distribution. You can use the Yocto Project out-of-the-box to create the +``poky-tiny`` distribution. Ultimately, you will want to make changes in +your own distribution that are likely modeled after ``poky-tiny``. + +.. note:: + + To use ``poky-tiny`` in your build, set the ``DISTRO`` variable in your + ``local.conf`` file to "poky-tiny" as described in the + ":ref:`dev-manual/common-tasks:creating your own distribution`" + section. + +Understanding some memory concepts will help you reduce the system size. +Memory consists of static, dynamic, and temporary memory. Static memory +is the TEXT (code), DATA (initialized data in the code), and BSS +(uninitialized data) sections. Dynamic memory represents memory that is +allocated at runtime: stacks, hash tables, and so forth. Temporary +memory is recovered after the boot process. This memory consists of +memory used for decompressing the kernel and for the ``__init__`` +functions. + +To help you see where you currently are with kernel and root filesystem +sizes, you can use two tools found in the :term:`Source Directory` +in the +``scripts/tiny/`` directory: + +- ``ksize.py``: Reports component sizes for the kernel build objects. + +- ``dirsize.py``: Reports component sizes for the root filesystem. + +This next tool and command help you organize configuration fragments and +view file dependencies in a human-readable form: + +- ``merge_config.sh``: Helps you manage configuration files and + fragments within the kernel. With this tool, you can merge individual + configuration fragments together. The tool allows you to make + overrides and warns you of any missing configuration options. The + tool is ideal for allowing you to iterate on configurations, create + minimal configurations, and create configuration files for different + machines without having to duplicate your process. + + The ``merge_config.sh`` script is part of the Linux Yocto kernel Git + repositories (i.e. ``linux-yocto-3.14``, ``linux-yocto-3.10``, + ``linux-yocto-3.8``, and so forth) in the ``scripts/kconfig`` + directory. + + For more information on configuration fragments, see the + ":ref:`kernel-dev/kernel-dev-common:creating configuration fragments`" + section in the Yocto Project Linux Kernel Development Manual. + +- ``bitbake -u taskexp -g bitbake_target``: Using the BitBake command + with these options brings up a Dependency Explorer from which you can + view file dependencies. Understanding these dependencies allows you + to make informed decisions when cutting out various pieces of the + kernel and root filesystem. + +Trim the Root Filesystem +~~~~~~~~~~~~~~~~~~~~~~~~ + +The root filesystem is made up of packages for booting, libraries, and +applications. To change things, you can configure how the packaging +happens, which changes the way you build them. You can also modify the +filesystem itself or select a different filesystem. + +First, find out what is hogging your root filesystem by running the +``dirsize.py`` script from your root directory: +:: + + $ cd root-directory-of-image + $ dirsize.py 100000 > dirsize-100k.log + $ cat dirsize-100k.log + +You can apply a filter to the script to ignore files +under a certain size. The previous example filters out any files below +100 Kbytes. The sizes reported by the tool are uncompressed, and thus +will be smaller by a relatively constant factor in a compressed root +filesystem. When you examine your log file, you can focus on areas of +the root filesystem that take up large amounts of memory. + +You need to be sure that what you eliminate does not cripple the +functionality you need. One way to see how packages relate to each other +is by using the Dependency Explorer UI with the BitBake command: +:: + + $ cd image-directory + $ bitbake -u taskexp -g image + +Use the interface to +select potential packages you wish to eliminate and see their dependency +relationships. + +When deciding how to reduce the size, get rid of packages that result in +minimal impact on the feature set. For example, you might not need a VGA +display. Or, you might be able to get by with ``devtmpfs`` and ``mdev`` +instead of ``udev``. + +Use your ``local.conf`` file to make changes. For example, to eliminate +``udev`` and ``glib``, set the following in the local configuration +file: +:: + + VIRTUAL-RUNTIME_dev_manager = "" + +Finally, you should consider exactly the type of root filesystem you +need to meet your needs while also reducing its size. For example, +consider ``cramfs``, ``squashfs``, ``ubifs``, ``ext2``, or an +``initramfs`` using ``initramfs``. Be aware that ``ext3`` requires a 1 +Mbyte journal. If you are okay with running read-only, you do not need +this journal. + +.. note:: + + After each round of elimination, you need to rebuild your system and + then use the tools to see the effects of your reductions. + +Trim the Kernel +~~~~~~~~~~~~~~~ + +The kernel is built by including policies for hardware-independent +aspects. What subsystems do you enable? For what architecture are you +building? Which drivers do you build by default? + +.. note:: + + You can modify the kernel source if you want to help with boot time. + +Run the ``ksize.py`` script from the top-level Linux build directory to +get an idea of what is making up the kernel: +:: + + $ cd top-level-linux-build-directory + $ ksize.py > ksize.log + $ cat ksize.log + +When you examine the log, you will see how much space is taken up with +the built-in ``.o`` files for drivers, networking, core kernel files, +filesystem, sound, and so forth. The sizes reported by the tool are +uncompressed, and thus will be smaller by a relatively constant factor +in a compressed kernel image. Look to reduce the areas that are large +and taking up around the "90% rule." + +To examine, or drill down, into any particular area, use the ``-d`` +option with the script: +:: + + $ ksize.py -d > ksize.log + +Using this option +breaks out the individual file information for each area of the kernel +(e.g. drivers, networking, and so forth). + +Use your log file to see what you can eliminate from the kernel based on +features you can let go. For example, if you are not going to need +sound, you do not need any drivers that support sound. + +After figuring out what to eliminate, you need to reconfigure the kernel +to reflect those changes during the next build. You could run +``menuconfig`` and make all your changes at once. However, that makes it +difficult to see the effects of your individual eliminations and also +makes it difficult to replicate the changes for perhaps another target +device. A better method is to start with no configurations using +``allnoconfig``, create configuration fragments for individual changes, +and then manage the fragments into a single configuration file using +``merge_config.sh``. The tool makes it easy for you to iterate using the +configuration change and build cycle. + +Each time you make configuration changes, you need to rebuild the kernel +and check to see what impact your changes had on the overall size. + +Remove Package Management Requirements +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Packaging requirements add size to the image. One way to reduce the size +of the image is to remove all the packaging requirements from the image. +This reduction includes both removing the package manager and its unique +dependencies as well as removing the package management data itself. + +To eliminate all the packaging requirements for an image, be sure that +"package-management" is not part of your +:term:`IMAGE_FEATURES` +statement for the image. When you remove this feature, you are removing +the package manager as well as its dependencies from the root +filesystem. + +Look for Other Ways to Minimize Size +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Depending on your particular circumstances, other areas that you can +trim likely exist. The key to finding these areas is through tools and +methods described here combined with experimentation and iteration. Here +are a couple of areas to experiment with: + +- ``glibc``: In general, follow this process: + + 1. Remove ``glibc`` features from + :term:`DISTRO_FEATURES` + that you think you do not need. + + 2. Build your distribution. + + 3. If the build fails due to missing symbols in a package, determine + if you can reconfigure the package to not need those features. For + example, change the configuration to not support wide character + support as is done for ``ncurses``. Or, if support for those + characters is needed, determine what ``glibc`` features provide + the support and restore the configuration. + + 4. Rebuild and repeat the process. + +- ``busybox``: For BusyBox, use a process similar as described for + ``glibc``. A difference is you will need to boot the resulting system + to see if you are able to do everything you expect from the running + system. You need to be sure to integrate configuration fragments into + Busybox because BusyBox handles its own core features and then allows + you to add configuration fragments on top. + +Iterate on the Process +~~~~~~~~~~~~~~~~~~~~~~ + +If you have not reached your goals on system size, you need to iterate +on the process. The process is the same. Use the tools and see just what +is taking up 90% of the root filesystem and the kernel. Decide what you +can eliminate without limiting your device beyond what you need. + +Depending on your system, a good place to look might be Busybox, which +provides a stripped down version of Unix tools in a single, executable +file. You might be able to drop virtual terminal services or perhaps +ipv6. + +Building Images for More than One Machine +----------------------------------------- + +A common scenario developers face is creating images for several +different machines that use the same software environment. In this +situation, it is tempting to set the tunings and optimization flags for +each build specifically for the targeted hardware (i.e. "maxing out" the +tunings). Doing so can considerably add to build times and package feed +maintenance collectively for the machines. For example, selecting tunes +that are extremely specific to a CPU core used in a system might enable +some micro optimizations in GCC for that particular system but would +otherwise not gain you much of a performance difference across the other +systems as compared to using a more general tuning across all the builds +(e.g. setting :term:`DEFAULTTUNE` +specifically for each machine's build). Rather than "max out" each +build's tunings, you can take steps that cause the OpenEmbedded build +system to reuse software across the various machines where it makes +sense. + +If build speed and package feed maintenance are considerations, you +should consider the points in this section that can help you optimize +your tunings to best consider build times and package feed maintenance. + +- *Share the Build Directory:* If at all possible, share the + :term:`TMPDIR` across builds. The + Yocto Project supports switching between different + :term:`MACHINE` values in the same + ``TMPDIR``. This practice is well supported and regularly used by + developers when building for multiple machines. When you use the same + ``TMPDIR`` for multiple machine builds, the OpenEmbedded build system + can reuse the existing native and often cross-recipes for multiple + machines. Thus, build time decreases. + + .. note:: + + If :term:`DISTRO` settings change or fundamental configuration settings + such as the filesystem layout, you need to work with a clean ``TMPDIR``. + Sharing ``TMPDIR`` under these circumstances might work but since it is + not guaranteed, you should use a clean ``TMPDIR``. + +- *Enable the Appropriate Package Architecture:* By default, the + OpenEmbedded build system enables three levels of package + architectures: "all", "tune" or "package", and "machine". Any given + recipe usually selects one of these package architectures (types) for + its output. Depending for what a given recipe creates packages, + making sure you enable the appropriate package architecture can + directly impact the build time. + + A recipe that just generates scripts can enable "all" architecture + because there are no binaries to build. To specifically enable "all" + architecture, be sure your recipe inherits the + :ref:`allarch <ref-classes-allarch>` class. + This class is useful for "all" architectures because it configures + many variables so packages can be used across multiple architectures. + + If your recipe needs to generate packages that are machine-specific + or when one of the build or runtime dependencies is already + machine-architecture dependent, which makes your recipe also + machine-architecture dependent, make sure your recipe enables the + "machine" package architecture through the + :term:`MACHINE_ARCH` + variable: + :: + + PACKAGE_ARCH = "${MACHINE_ARCH}" + + When you do not + specifically enable a package architecture through the + :term:`PACKAGE_ARCH`, The + OpenEmbedded build system defaults to the + :term:`TUNE_PKGARCH` setting: + :: + + PACKAGE_ARCH = "${TUNE_PKGARCH}" + +- *Choose a Generic Tuning File if Possible:* Some tunes are more + generic and can run on multiple targets (e.g. an ``armv5`` set of + packages could run on ``armv6`` and ``armv7`` processors in most + cases). Similarly, ``i486`` binaries could work on ``i586`` and + higher processors. You should realize, however, that advances on + newer processor versions would not be used. + + If you select the same tune for several different machines, the + OpenEmbedded build system reuses software previously built, thus + speeding up the overall build time. Realize that even though a new + sysroot for each machine is generated, the software is not recompiled + and only one package feed exists. + +- *Manage Granular Level Packaging:* Sometimes cases exist where + injecting another level of package architecture beyond the three + higher levels noted earlier can be useful. For example, consider how + NXP (formerly Freescale) allows for the easy reuse of binary packages + in their layer + :yocto_git:`meta-freescale </meta-freescale/>`. + In this example, the + :yocto_git:`fsl-dynamic-packagearch </meta-freescale/tree/classes/fsl-dynamic-packagearch.bbclass>` + class shares GPU packages for i.MX53 boards because all boards share + the AMD GPU. The i.MX6-based boards can do the same because all + boards share the Vivante GPU. This class inspects the BitBake + datastore to identify if the package provides or depends on one of + the sub-architecture values. If so, the class sets the + :term:`PACKAGE_ARCH` value + based on the ``MACHINE_SUBARCH`` value. If the package does not + provide or depend on one of the sub-architecture values but it + matches a value in the machine-specific filter, it sets + :term:`MACHINE_ARCH`. This + behavior reduces the number of packages built and saves build time by + reusing binaries. + +- *Use Tools to Debug Issues:* Sometimes you can run into situations + where software is being rebuilt when you think it should not be. For + example, the OpenEmbedded build system might not be using shared + state between machines when you think it should be. These types of + situations are usually due to references to machine-specific + variables such as :term:`MACHINE`, + :term:`SERIAL_CONSOLES`, + :term:`XSERVER`, + :term:`MACHINE_FEATURES`, + and so forth in code that is supposed to only be tune-specific or + when the recipe depends + (:term:`DEPENDS`, + :term:`RDEPENDS`, + :term:`RRECOMMENDS`, + :term:`RSUGGESTS`, and so forth) + on some other recipe that already has + :term:`PACKAGE_ARCH` defined + as "${MACHINE_ARCH}". + + .. note:: + + Patches to fix any issues identified are most welcome as these + issues occasionally do occur. + + For such cases, you can use some tools to help you sort out the + situation: + + - ``state-diff-machines.sh``*:* You can find this tool in the + ``scripts`` directory of the Source Repositories. See the comments + in the script for information on how to use the tool. + + - *BitBake's "-S printdiff" Option:* Using this option causes + BitBake to try to establish the closest signature match it can + (e.g. in the shared state cache) and then run ``bitbake-diffsigs`` + over the matches to determine the stamps and delta where these two + stamp trees diverge. + +Building Software from an External Source +----------------------------------------- + +By default, the OpenEmbedded build system uses the +:term:`Build Directory` when building source +code. The build process involves fetching the source files, unpacking +them, and then patching them if necessary before the build takes place. + +Situations exist where you might want to build software from source +files that are external to and thus outside of the OpenEmbedded build +system. For example, suppose you have a project that includes a new BSP +with a heavily customized kernel. And, you want to minimize exposing the +build system to the development team so that they can focus on their +project and maintain everyone's workflow as much as possible. In this +case, you want a kernel source directory on the development machine +where the development occurs. You want the recipe's +:term:`SRC_URI` variable to point to +the external directory and use it as is, not copy it. + +To build from software that comes from an external source, all you need +to do is inherit the +:ref:`externalsrc <ref-classes-externalsrc>` class +and then set the +:term:`EXTERNALSRC` variable to +point to your external source code. Here are the statements to put in +your ``local.conf`` file: +:: + + INHERIT += "externalsrc" + EXTERNALSRC_pn-myrecipe = "path-to-your-source-tree" + +This next example shows how to accomplish the same thing by setting +``EXTERNALSRC`` in the recipe itself or in the recipe's append file: +:: + + EXTERNALSRC = "path" + EXTERNALSRC_BUILD = "path" + +.. note:: + + In order for these settings to take effect, you must globally or + locally inherit the :ref:`externalsrc <ref-classes-externalsrc>` + class. + +By default, ``externalsrc.bbclass`` builds the source code in a +directory separate from the external source directory as specified by +:term:`EXTERNALSRC`. If you need +to have the source built in the same directory in which it resides, or +some other nominated directory, you can set +:term:`EXTERNALSRC_BUILD` +to point to that directory: +:: + + EXTERNALSRC_BUILD_pn-myrecipe = "path-to-your-source-tree" + +Replicating a Build Offline +--------------------------- + +It can be useful to take a "snapshot" of upstream sources used in a +build and then use that "snapshot" later to replicate the build offline. +To do so, you need to first prepare and populate your downloads +directory your "snapshot" of files. Once your downloads directory is +ready, you can use it at any time and from any machine to replicate your +build. + +Follow these steps to populate your Downloads directory: + +1. *Create a Clean Downloads Directory:* Start with an empty downloads + directory (:term:`DL_DIR`). You + start with an empty downloads directory by either removing the files + in the existing directory or by setting ``DL_DIR`` to point to either + an empty location or one that does not yet exist. + +2. *Generate Tarballs of the Source Git Repositories:* Edit your + ``local.conf`` configuration file as follows: + :: + + DL_DIR = "/home/your-download-dir/" + BB_GENERATE_MIRROR_TARBALLS = "1" + + During + the fetch process in the next step, BitBake gathers the source files + and creates tarballs in the directory pointed to by ``DL_DIR``. See + the + :term:`BB_GENERATE_MIRROR_TARBALLS` + variable for more information. + +3. *Populate Your Downloads Directory Without Building:* Use BitBake to + fetch your sources but inhibit the build: + :: + + $ bitbake target --runonly=fetch + + The downloads directory (i.e. ``${DL_DIR}``) now has + a "snapshot" of the source files in the form of tarballs, which can + be used for the build. + +4. *Optionally Remove Any Git or other SCM Subdirectories From the + Downloads Directory:* If you want, you can clean up your downloads + directory by removing any Git or other Source Control Management + (SCM) subdirectories such as ``${DL_DIR}/git2/*``. The tarballs + already contain these subdirectories. + +Once your downloads directory has everything it needs regarding source +files, you can create your "own-mirror" and build your target. +Understand that you can use the files to build the target offline from +any machine and at any time. + +Follow these steps to build your target using the files in the downloads +directory: + +1. *Using Local Files Only:* Inside your ``local.conf`` file, add the + :term:`SOURCE_MIRROR_URL` + variable, inherit the + :ref:`own-mirrors <ref-classes-own-mirrors>` + class, and use the + :term:`bitbake:BB_NO_NETWORK` + variable to your ``local.conf``. + :: + + SOURCE_MIRROR_URL ?= "file:///home/your-download-dir/" + INHERIT += "own-mirrors" + BB_NO_NETWORK = "1" + + The ``SOURCE_MIRROR_URL`` and ``own-mirror`` + class set up the system to use the downloads directory as your "own + mirror". Using the ``BB_NO_NETWORK`` variable makes sure that + BitBake's fetching process in step 3 stays local, which means files + from your "own-mirror" are used. + +2. *Start With a Clean Build:* You can start with a clean build by + removing the + ``${``\ :term:`TMPDIR`\ ``}`` + directory or using a new :term:`Build Directory`. + +3. *Build Your Target:* Use BitBake to build your target: + :: + + $ bitbake target + + The build completes using the known local "snapshot" of source + files from your mirror. The resulting tarballs for your "snapshot" of + source files are in the downloads directory. + + .. note:: + + The offline build does not work if recipes attempt to find the + latest version of software by setting + :term:`SRCREV` to + ``${``\ :term:`AUTOREV`\ ``}``: + :: + + SRCREV = "${AUTOREV}" + + When a recipe sets ``SRCREV`` to + ``${AUTOREV}``, the build system accesses the network in an + attempt to determine the latest version of software from the SCM. + Typically, recipes that use ``AUTOREV`` are custom or modified + recipes. Recipes that reside in public repositories usually do not + use ``AUTOREV``. + + If you do have recipes that use ``AUTOREV``, you can take steps to + still use the recipes in an offline build. Do the following: + + 1. Use a configuration generated by enabling `build + history <#maintaining-build-output-quality>`__. + + 2. Use the ``buildhistory-collect-srcrevs`` command to collect the + stored ``SRCREV`` values from the build's history. For more + information on collecting these values, see the "`Build History + Package Information <#build-history-package-information>`__" + section. + + 3. Once you have the correct source revisions, you can modify + those recipes to to set ``SRCREV`` to specific versions of the + software. + +Speeding Up a Build +=================== + +Build time can be an issue. By default, the build system uses simple +controls to try and maximize build efficiency. In general, the default +settings for all the following variables result in the most efficient +build times when dealing with single socket systems (i.e. a single CPU). +If you have multiple CPUs, you might try increasing the default values +to gain more speed. See the descriptions in the glossary for each +variable for more information: + +- :term:`BB_NUMBER_THREADS`: + The maximum number of threads BitBake simultaneously executes. + +- :term:`bitbake:BB_NUMBER_PARSE_THREADS`: + The number of threads BitBake uses during parsing. + +- :term:`PARALLEL_MAKE`: Extra + options passed to the ``make`` command during the + :ref:`ref-tasks-compile` task in + order to specify parallel compilation on the local build host. + +- :term:`PARALLEL_MAKEINST`: + Extra options passed to the ``make`` command during the + :ref:`ref-tasks-install` task in + order to specify parallel installation on the local build host. + +As mentioned, these variables all scale to the number of processor cores +available on the build system. For single socket systems, this +auto-scaling ensures that the build system fundamentally takes advantage +of potential parallel operations during the build based on the build +machine's capabilities. + +Following are additional factors that can affect build speed: + +- File system type: The file system type that the build is being + performed on can also influence performance. Using ``ext4`` is + recommended as compared to ``ext2`` and ``ext3`` due to ``ext4`` + improved features such as extents. + +- Disabling the updating of access time using ``noatime``: The + ``noatime`` mount option prevents the build system from updating file + and directory access times. + +- Setting a longer commit: Using the "commit=" mount option increases + the interval in seconds between disk cache writes. Changing this + interval from the five second default to something longer increases + the risk of data loss but decreases the need to write to the disk, + thus increasing the build performance. + +- Choosing the packaging backend: Of the available packaging backends, + IPK is the fastest. Additionally, selecting a singular packaging + backend also helps. + +- Using ``tmpfs`` for :term:`TMPDIR` + as a temporary file system: While this can help speed up the build, + the benefits are limited due to the compiler using ``-pipe``. The + build system goes to some lengths to avoid ``sync()`` calls into the + file system on the principle that if there was a significant failure, + the :term:`Build Directory` + contents could easily be rebuilt. + +- Inheriting the + :ref:`rm_work <ref-classes-rm-work>` class: + Inheriting this class has shown to speed up builds due to + significantly lower amounts of data stored in the data cache as well + as on disk. Inheriting this class also makes cleanup of + :term:`TMPDIR` faster, at the + expense of being easily able to dive into the source code. File + system maintainers have recommended that the fastest way to clean up + large numbers of files is to reformat partitions rather than delete + files due to the linear nature of partitions. This, of course, + assumes you structure the disk partitions and file systems in a way + that this is practical. + +Aside from the previous list, you should keep some trade offs in mind +that can help you speed up the build: + +- Remove items from + :term:`DISTRO_FEATURES` + that you might not need. + +- Exclude debug symbols and other debug information: If you do not need + these symbols and other debug information, disabling the ``*-dbg`` + package generation can speed up the build. You can disable this + generation by setting the + :term:`INHIBIT_PACKAGE_DEBUG_SPLIT` + variable to "1". + +- Disable static library generation for recipes derived from + ``autoconf`` or ``libtool``: Following is an example showing how to + disable static libraries and still provide an override to handle + exceptions: + :: + + STATICLIBCONF = "--disable-static" + STATICLIBCONF_sqlite3-native = "" + EXTRA_OECONF += "${STATICLIBCONF}" + + .. note:: + + - Some recipes need static libraries in order to work correctly + (e.g. ``pseudo-native`` needs ``sqlite3-native``). Overrides, + as in the previous example, account for these kinds of + exceptions. + + - Some packages have packaging code that assumes the presence of + the static libraries. If so, you might need to exclude them as + well. + +Working With Libraries +====================== + +Libraries are an integral part of your system. This section describes +some common practices you might find helpful when working with libraries +to build your system: + +- `How to include static library + files <#including-static-library-files>`__ + +- `How to use the Multilib feature to combine multiple versions of + library files into a single + image <#combining-multiple-versions-library-files-into-one-image>`__ + +- `How to install multiple versions of the same library in parallel on + the same + system <#installing-multiple-versions-of-the-same-library>`__ + +Including Static Library Files +------------------------------ + +If you are building a library and the library offers static linking, you +can control which static library files (``*.a`` files) get included in +the built library. + +The :term:`PACKAGES` and +:term:`FILES_* <FILES>` variables in the +``meta/conf/bitbake.conf`` configuration file define how files installed +by the ``do_install`` task are packaged. By default, the ``PACKAGES`` +variable includes ``${PN}-staticdev``, which represents all static +library files. + +.. note:: + + Some previously released versions of the Yocto Project defined the + static library files through ``${PN}-dev``. + +Following is part of the BitBake configuration file, where you can see +how the static library files are defined: +:: + + PACKAGE_BEFORE_PN ?= "" + PACKAGES = "${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}" + PACKAGES_DYNAMIC = "^${PN}-locale-.*" + FILES = "" + + FILES_${PN} = "${bindir}/* ${sbindir}/* ${libexecdir}/* ${libdir}/lib*${SOLIBS} \ + ${sysconfdir} ${sharedstatedir} ${localstatedir} \ + ${base_bindir}/* ${base_sbindir}/* \ + ${base_libdir}/*${SOLIBS} \ + ${base_prefix}/lib/udev/rules.d ${prefix}/lib/udev/rules.d \ + ${datadir}/${BPN} ${libdir}/${BPN}/* \ + ${datadir}/pixmaps ${datadir}/applications \ + ${datadir}/idl ${datadir}/omf ${datadir}/sounds \ + ${libdir}/bonobo/servers" + + FILES_${PN}-bin = "${bindir}/* ${sbindir}/*" + + FILES_${PN}-doc = "${docdir} ${mandir} ${infodir} ${datadir}/gtk-doc \ + ${datadir}/gnome/help" + SECTION_${PN}-doc = "doc" + + FILES_SOLIBSDEV ?= "${base_libdir}/lib*${SOLIBSDEV} ${libdir}/lib*${SOLIBSDEV}" + FILES_${PN}-dev = "${includedir} ${FILES_SOLIBSDEV} ${libdir}/*.la \ + ${libdir}/*.o ${libdir}/pkgconfig ${datadir}/pkgconfig \ + ${datadir}/aclocal ${base_libdir}/*.o \ + ${libdir}/${BPN}/*.la ${base_libdir}/*.la" + SECTION_${PN}-dev = "devel" + ALLOW_EMPTY_${PN}-dev = "1" + RDEPENDS_${PN}-dev = "${PN} (= ${EXTENDPKGV})" + + FILES_${PN}-staticdev = "${libdir}/*.a ${base_libdir}/*.a ${libdir}/${BPN}/*.a" + SECTION_${PN}-staticdev = "devel" + RDEPENDS_${PN}-staticdev = "${PN}-dev (= ${EXTENDPKGV})" + +Combining Multiple Versions of Library Files into One Image +----------------------------------------------------------- + +The build system offers the ability to build libraries with different +target optimizations or architecture formats and combine these together +into one system image. You can link different binaries in the image +against the different libraries as needed for specific use cases. This +feature is called "Multilib". + +An example would be where you have most of a system compiled in 32-bit +mode using 32-bit libraries, but you have something large, like a +database engine, that needs to be a 64-bit application and uses 64-bit +libraries. Multilib allows you to get the best of both 32-bit and 64-bit +libraries. + +While the Multilib feature is most commonly used for 32 and 64-bit +differences, the approach the build system uses facilitates different +target optimizations. You could compile some binaries to use one set of +libraries and other binaries to use a different set of libraries. The +libraries could differ in architecture, compiler options, or other +optimizations. + +Several examples exist in the ``meta-skeleton`` layer found in the +:term:`Source Directory`: + +- ``conf/multilib-example.conf`` configuration file + +- ``conf/multilib-example2.conf`` configuration file + +- ``recipes-multilib/images/core-image-multilib-example.bb`` recipe + +Preparing to Use Multilib +~~~~~~~~~~~~~~~~~~~~~~~~~ + +User-specific requirements drive the Multilib feature. Consequently, +there is no one "out-of-the-box" configuration that likely exists to +meet your needs. + +In order to enable Multilib, you first need to ensure your recipe is +extended to support multiple libraries. Many standard recipes are +already extended and support multiple libraries. You can check in the +``meta/conf/multilib.conf`` configuration file in the +:term:`Source Directory` to see how this is +done using the +:term:`BBCLASSEXTEND` variable. +Eventually, all recipes will be covered and this list will not be +needed. + +For the most part, the Multilib class extension works automatically to +extend the package name from ``${PN}`` to ``${MLPREFIX}${PN}``, where +``MLPREFIX`` is the particular multilib (e.g. "lib32-" or "lib64-"). +Standard variables such as +:term:`DEPENDS`, +:term:`RDEPENDS`, +:term:`RPROVIDES`, +:term:`RRECOMMENDS`, +:term:`PACKAGES`, and +:term:`PACKAGES_DYNAMIC` are +automatically extended by the system. If you are extending any manual +code in the recipe, you can use the ``${MLPREFIX}`` variable to ensure +those names are extended correctly. This automatic extension code +resides in ``multilib.bbclass``. + +Using Multilib +~~~~~~~~~~~~~~ + +After you have set up the recipes, you need to define the actual +combination of multiple libraries you want to build. You accomplish this +through your ``local.conf`` configuration file in the +:term:`Build Directory`. An example +configuration would be as follows: +:: + + MACHINE = "qemux86-64" + require conf/multilib.conf + MULTILIBS = "multilib:lib32" + DEFAULTTUNE_virtclass-multilib-lib32 = "x86" + IMAGE_INSTALL_append = "lib32-glib-2.0" + +This example enables an additional library named +``lib32`` alongside the normal target packages. When combining these +"lib32" alternatives, the example uses "x86" for tuning. For information +on this particular tuning, see +``meta/conf/machine/include/ia32/arch-ia32.inc``. + +The example then includes ``lib32-glib-2.0`` in all the images, which +illustrates one method of including a multiple library dependency. You +can use a normal image build to include this dependency, for example: +:: + + $ bitbake core-image-sato + +You can also build Multilib packages +specifically with a command like this: +:: + + $ bitbake lib32-glib-2.0 + +Additional Implementation Details +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Generic implementation details as well as details that are specific to +package management systems exist. Following are implementation details +that exist regardless of the package management system: + +- The typical convention used for the class extension code as used by + Multilib assumes that all package names specified in + :term:`PACKAGES` that contain + ``${PN}`` have ``${PN}`` at the start of the name. When that + convention is not followed and ``${PN}`` appears at the middle or the + end of a name, problems occur. + +- The :term:`TARGET_VENDOR` + value under Multilib will be extended to "-vendormlmultilib" (e.g. + "-pokymllib32" for a "lib32" Multilib with Poky). The reason for this + slightly unwieldy contraction is that any "-" characters in the + vendor string presently break Autoconf's ``config.sub``, and other + separators are problematic for different reasons. + +For the RPM Package Management System, the following implementation +details exist: + +- A unique architecture is defined for the Multilib packages, along + with creating a unique deploy folder under ``tmp/deploy/rpm`` in the + :term:`Build Directory`. For + example, consider ``lib32`` in a ``qemux86-64`` image. The possible + architectures in the system are "all", "qemux86_64", + "lib32_qemux86_64", and "lib32_x86". + +- The ``${MLPREFIX}`` variable is stripped from ``${PN}`` during RPM + packaging. The naming for a normal RPM package and a Multilib RPM + package in a ``qemux86-64`` system resolves to something similar to + ``bash-4.1-r2.x86_64.rpm`` and ``bash-4.1.r2.lib32_x86.rpm``, + respectively. + +- When installing a Multilib image, the RPM backend first installs the + base image and then installs the Multilib libraries. + +- The build system relies on RPM to resolve the identical files in the + two (or more) Multilib packages. + +For the IPK Package Management System, the following implementation +details exist: + +- The ``${MLPREFIX}`` is not stripped from ``${PN}`` during IPK + packaging. The naming for a normal RPM package and a Multilib IPK + package in a ``qemux86-64`` system resolves to something like + ``bash_4.1-r2.x86_64.ipk`` and ``lib32-bash_4.1-rw_x86.ipk``, + respectively. + +- The IPK deploy folder is not modified with ``${MLPREFIX}`` because + packages with and without the Multilib feature can exist in the same + folder due to the ``${PN}`` differences. + +- IPK defines a sanity check for Multilib installation using certain + rules for file comparison, overridden, etc. + +Installing Multiple Versions of the Same Library +------------------------------------------------ + +Situations can exist where you need to install and use multiple versions +of the same library on the same system at the same time. These +situations almost always exist when a library API changes and you have +multiple pieces of software that depend on the separate versions of the +library. To accommodate these situations, you can install multiple +versions of the same library in parallel on the same system. + +The process is straightforward as long as the libraries use proper +versioning. With properly versioned libraries, all you need to do to +individually specify the libraries is create separate, appropriately +named recipes where the :term:`PN` part of +the name includes a portion that differentiates each library version +(e.g. the major part of the version number). Thus, instead of having a +single recipe that loads one version of a library (e.g. ``clutter``), +you provide multiple recipes that result in different versions of the +libraries you want. As an example, the following two recipes would allow +the two separate versions of the ``clutter`` library to co-exist on the +same system: + +.. code-block:: none + + clutter-1.6_1.6.20.bb + clutter-1.8_1.8.4.bb + +Additionally, if +you have other recipes that depend on a given library, you need to use +the :term:`DEPENDS` variable to +create the dependency. Continuing with the same example, if you want to +have a recipe depend on the 1.8 version of the ``clutter`` library, use +the following in your recipe: +:: + + DEPENDS = "clutter-1.8" + +Using x32 psABI +=============== + +x32 processor-specific Application Binary Interface (`x32 +psABI <https://software.intel.com/en-us/node/628948>`__) is a native +32-bit processor-specific ABI for Intel 64 (x86-64) architectures. An +ABI defines the calling conventions between functions in a processing +environment. The interface determines what registers are used and what +the sizes are for various C data types. + +Some processing environments prefer using 32-bit applications even when +running on Intel 64-bit platforms. Consider the i386 psABI, which is a +very old 32-bit ABI for Intel 64-bit platforms. The i386 psABI does not +provide efficient use and access of the Intel 64-bit processor +resources, leaving the system underutilized. Now consider the x86_64 +psABI. This ABI is newer and uses 64-bits for data sizes and program +pointers. The extra bits increase the footprint size of the programs, +libraries, and also increases the memory and file system size +requirements. Executing under the x32 psABI enables user programs to +utilize CPU and system resources more efficiently while keeping the +memory footprint of the applications low. Extra bits are used for +registers but not for addressing mechanisms. + +The Yocto Project supports the final specifications of x32 psABI as +follows: + +- You can create packages and images in x32 psABI format on x86_64 + architecture targets. + +- You can successfully build recipes with the x32 toolchain. + +- You can create and boot ``core-image-minimal`` and + ``core-image-sato`` images. + +- RPM Package Manager (RPM) support exists for x32 binaries. + +- Support for large images exists. + +To use the x32 psABI, you need to edit your ``conf/local.conf`` +configuration file as follows: +:: + + MACHINE = "qemux86-64" + DEFAULTTUNE = "x86-64-x32" + baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE') \ + or 'INVALID')) or 'lib'}" + +Once you have set +up your configuration file, use BitBake to build an image that supports +the x32 psABI. Here is an example: +:: + + $ bitbake core-image-sato + +Enabling GObject Introspection Support +====================================== + +`GObject +introspection <https://wiki.gnome.org/Projects/GObjectIntrospection>`__ +is the standard mechanism for accessing GObject-based software from +runtime environments. GObject is a feature of the GLib library that +provides an object framework for the GNOME desktop and related software. +GObject Introspection adds information to GObject that allows objects +created within it to be represented across different programming +languages. If you want to construct GStreamer pipelines using Python, or +control UPnP infrastructure using Javascript and GUPnP, GObject +introspection is the only way to do it. + +This section describes the Yocto Project support for generating and +packaging GObject introspection data. GObject introspection data is a +description of the API provided by libraries built on top of GLib +framework, and, in particular, that framework's GObject mechanism. +GObject Introspection Repository (GIR) files go to ``-dev`` packages, +``typelib`` files go to main packages as they are packaged together with +libraries that are introspected. + +The data is generated when building such a library, by linking the +library with a small executable binary that asks the library to describe +itself, and then executing the binary and processing its output. + +Generating this data in a cross-compilation environment is difficult +because the library is produced for the target architecture, but its +code needs to be executed on the build host. This problem is solved with +the OpenEmbedded build system by running the code through QEMU, which +allows precisely that. Unfortunately, QEMU does not always work +perfectly as mentioned in the "`Known Issues <#known-issues>`__" +section. + +Enabling the Generation of Introspection Data +--------------------------------------------- + +Enabling the generation of introspection data (GIR files) in your +library package involves the following: + +1. Inherit the + :ref:`gobject-introspection <ref-classes-gobject-introspection>` + class. + +2. Make sure introspection is not disabled anywhere in the recipe or + from anything the recipe includes. Also, make sure that + "gobject-introspection-data" is not in + :term:`DISTRO_FEATURES_BACKFILL_CONSIDERED` + and that "qemu-usermode" is not in + :term:`MACHINE_FEATURES_BACKFILL_CONSIDERED`. + If either of these conditions exist, nothing will happen. + +3. Try to build the recipe. If you encounter build errors that look like + something is unable to find ``.so`` libraries, check where these + libraries are located in the source tree and add the following to the + recipe: + :: + + GIR_EXTRA_LIBS_PATH = "${B}/something/.libs" + + .. note:: + + See recipes in the ``oe-core`` repository that use that + ``GIR_EXTRA_LIBS_PATH`` variable as an example. + +4. Look for any other errors, which probably mean that introspection + support in a package is not entirely standard, and thus breaks down + in a cross-compilation environment. For such cases, custom-made fixes + are needed. A good place to ask and receive help in these cases is + the :ref:`Yocto Project mailing + lists <resources-mailinglist>`. + +.. note:: + + Using a library that no longer builds against the latest Yocto + Project release and prints introspection related errors is a good + candidate for the previous procedure. + +Disabling the Generation of Introspection Data +---------------------------------------------- + +You might find that you do not want to generate introspection data. Or, +perhaps QEMU does not work on your build host and target architecture +combination. If so, you can use either of the following methods to +disable GIR file generations: + +- Add the following to your distro configuration: + :: + + DISTRO_FEATURES_BACKFILL_CONSIDERED = "gobject-introspection-data" + + Adding this statement disables generating introspection data using + QEMU but will still enable building introspection tools and libraries + (i.e. building them does not require the use of QEMU). + +- Add the following to your machine configuration: + :: + + MACHINE_FEATURES_BACKFILL_CONSIDERED = "qemu-usermode" + + Adding this statement disables the use of QEMU when building packages for your + machine. Currently, this feature is used only by introspection + recipes and has the same effect as the previously described option. + + .. note:: + + Future releases of the Yocto Project might have other features + affected by this option. + +If you disable introspection data, you can still obtain it through other +means such as copying the data from a suitable sysroot, or by generating +it on the target hardware. The OpenEmbedded build system does not +currently provide specific support for these techniques. + +Testing that Introspection Works in an Image +-------------------------------------------- + +Use the following procedure to test if generating introspection data is +working in an image: + +1. Make sure that "gobject-introspection-data" is not in + :term:`DISTRO_FEATURES_BACKFILL_CONSIDERED` + and that "qemu-usermode" is not in + :term:`MACHINE_FEATURES_BACKFILL_CONSIDERED`. + +2. Build ``core-image-sato``. + +3. Launch a Terminal and then start Python in the terminal. + +4. Enter the following in the terminal: + :: + + >>> from gi.repository import GLib + >>> GLib.get_host_name() + +5. For something a little more advanced, enter the following see: + https://python-gtk-3-tutorial.readthedocs.io/en/latest/introduction.html + +Known Issues +------------ + +The following know issues exist for GObject Introspection Support: + +- ``qemu-ppc64`` immediately crashes. Consequently, you cannot build + introspection data on that architecture. + +- x32 is not supported by QEMU. Consequently, introspection data is + disabled. + +- musl causes transient GLib binaries to crash on assertion failures. + Consequently, generating introspection data is disabled. + +- Because QEMU is not able to run the binaries correctly, introspection + is disabled for some specific packages under specific architectures + (e.g. ``gcr``, ``libsecret``, and ``webkit``). + +- QEMU usermode might not work properly when running 64-bit binaries + under 32-bit host machines. In particular, "qemumips64" is known to + not work under i686. + +Optionally Using an External Toolchain +====================================== + +You might want to use an external toolchain as part of your development. +If this is the case, the fundamental steps you need to accomplish are as +follows: + +- Understand where the installed toolchain resides. For cases where you + need to build the external toolchain, you would need to take separate + steps to build and install the toolchain. + +- Make sure you add the layer that contains the toolchain to your + ``bblayers.conf`` file through the + :term:`BBLAYERS` variable. + +- Set the ``EXTERNAL_TOOLCHAIN`` variable in your ``local.conf`` file + to the location in which you installed the toolchain. + +A good example of an external toolchain used with the Yocto Project is +Mentor Graphics Sourcery G++ Toolchain. You can see information on how +to use that particular layer in the ``README`` file at +https://github.com/MentorEmbedded/meta-sourcery/. You can find +further information by reading about the +:term:`TCMODE` variable in the Yocto +Project Reference Manual's variable glossary. + +Creating Partitioned Images Using Wic +===================================== + +Creating an image for a particular hardware target using the +OpenEmbedded build system does not necessarily mean you can boot that +image as is on your device. Physical devices accept and boot images in +various ways depending on the specifics of the device. Usually, +information about the hardware can tell you what image format the device +requires. Should your device require multiple partitions on an SD card, +flash, or an HDD, you can use the OpenEmbedded Image Creator, Wic, to +create the properly partitioned image. + +The ``wic`` command generates partitioned images from existing +OpenEmbedded build artifacts. Image generation is driven by partitioning +commands contained in an Openembedded kickstart file (``.wks``) +specified either directly on the command line or as one of a selection +of canned kickstart files as shown with the ``wic list images`` command +in the "`Using an Existing Kickstart +File <#using-a-provided-kickstart-file>`__" section. When you apply the +command to a given set of build artifacts, the result is an image or set +of images that can be directly written onto media and used on a +particular system. + +.. note:: + + For a kickstart file reference, see the + ":ref:`ref-manual/ref-kickstart:openembedded kickstart (\`\`.wks\`\`) reference`" + Chapter in the Yocto Project Reference Manual. + +The ``wic`` command and the infrastructure it is based on is by +definition incomplete. The purpose of the command is to allow the +generation of customized images, and as such, was designed to be +completely extensible through a plugin interface. See the "`Using the +Wic PlugIn Interface <#wic-using-the-wic-plugin-interface>`__" section +for information on these plugins. + +This section provides some background information on Wic, describes what +you need to have in place to run the tool, provides instruction on how +to use the Wic utility, provides information on using the Wic plugins +interface, and provides several examples that show how to use Wic. + +Background +---------- + +This section provides some background on the Wic utility. While none of +this information is required to use Wic, you might find it interesting. + +- The name "Wic" is derived from OpenEmbedded Image Creator (oeic). The + "oe" diphthong in "oeic" was promoted to the letter "w", because + "oeic" is both difficult to remember and to pronounce. + +- Wic is loosely based on the Meego Image Creator (``mic``) framework. + The Wic implementation has been heavily modified to make direct use + of OpenEmbedded build artifacts instead of package installation and + configuration, which are already incorporated within the OpenEmbedded + artifacts. + +- Wic is a completely independent standalone utility that initially + provides easier-to-use and more flexible replacements for an existing + functionality in OE-Core's + :ref:`image-live <ref-classes-image-live>` + class. The difference between Wic and those examples is that with Wic + the functionality of those scripts is implemented by a + general-purpose partitioning language, which is based on Redhat + kickstart syntax. + +Requirements +------------ + +In order to use the Wic utility with the OpenEmbedded Build system, your +system needs to meet the following requirements: + +- The Linux distribution on your development host must support the + Yocto Project. See the ":ref:`detailed-supported-distros`" + section in the Yocto Project Reference Manual for the list of + distributions that support the Yocto Project. + +- The standard system utilities, such as ``cp``, must be installed on + your development host system. + +- You must have sourced the build environment setup script (i.e. + :ref:`structure-core-script`) found in the + :term:`Build Directory`. + +- You need to have the build artifacts already available, which + typically means that you must have already created an image using the + Openembedded build system (e.g. ``core-image-minimal``). While it + might seem redundant to generate an image in order to create an image + using Wic, the current version of Wic requires the artifacts in the + form generated by the OpenEmbedded build system. + +- You must build several native tools, which are built to run on the + build system: + :: + + $ bitbake parted-native dosfstools-native mtools-native + +- Include "wic" as part of the + :term:`IMAGE_FSTYPES` + variable. + +- Include the name of the :ref:`wic kickstart file <openembedded-kickstart-wks-reference>` + as part of the :term:`WKS_FILE` variable + +Getting Help +------------ + +You can get general help for the ``wic`` command by entering the ``wic`` +command by itself or by entering the command with a help argument as +follows: +:: + + $ wic -h + $ wic --help + $ wic help + +Currently, Wic supports seven commands: ``cp``, ``create``, ``help``, +``list``, ``ls``, ``rm``, and ``write``. You can get help for all these +commands except "help" by using the following form: +:: + + $ wic help command + +For example, the following command returns help for the ``write`` +command: +:: + + $ wic help write + +Wic supports help for three topics: ``overview``, ``plugins``, and +``kickstart``. You can get help for any topic using the following form: +:: + + $ wic help topic + +For example, the following returns overview help for Wic: +:: + + $ wic help overview + +One additional level of help exists for Wic. You can get help on +individual images through the ``list`` command. You can use the ``list`` +command to return the available Wic images as follows: +:: + + $ wic list images + genericx86 Create an EFI disk image for genericx86* + beaglebone-yocto Create SD card image for Beaglebone + edgerouter Create SD card image for Edgerouter + qemux86-directdisk Create a qemu machine 'pcbios' direct disk image + directdisk-gpt Create a 'pcbios' direct disk image + mkefidisk Create an EFI disk image + directdisk Create a 'pcbios' direct disk image + systemd-bootdisk Create an EFI disk image with systemd-boot + mkhybridiso Create a hybrid ISO image + sdimage-bootpart Create SD card image with a boot partition + directdisk-multi-rootfs Create multi rootfs image using rootfs plugin + directdisk-bootloader-config Create a 'pcbios' direct disk image with custom bootloader config + +Once you know the list of available +Wic images, you can use ``help`` with the command to get help on a +particular image. For example, the following command returns help on the +"beaglebone-yocto" image: +:: + + $ wic list beaglebone-yocto help + + Creates a partitioned SD card image for Beaglebone. + Boot files are located in the first vfat partition. + +Operational Modes +----------------- + +You can use Wic in two different modes, depending on how much control +you need for specifying the Openembedded build artifacts that are used +for creating the image: Raw and Cooked: + +- *Raw Mode:* You explicitly specify build artifacts through Wic + command-line arguments. + +- *Cooked Mode:* The current + :term:`MACHINE` setting and image + name are used to automatically locate and provide the build + artifacts. You just supply a kickstart file and the name of the image + from which to use artifacts. + +Regardless of the mode you use, you need to have the build artifacts +ready and available. + +Raw Mode +~~~~~~~~ + +Running Wic in raw mode allows you to specify all the partitions through +the ``wic`` command line. The primary use for raw mode is if you have +built your kernel outside of the Yocto Project +:term:`Build Directory`. In other words, you +can point to arbitrary kernel, root filesystem locations, and so forth. +Contrast this behavior with cooked mode where Wic looks in the Build +Directory (e.g. ``tmp/deploy/images/``\ machine). + +The general form of the ``wic`` command in raw mode is: +:: + + $ wic create wks_file options ... + + Where: + + wks_file: + An OpenEmbedded kickstart file. You can provide + your own custom file or use a file from a set of + existing files as described by further options. + + optional arguments: + -h, --help show this help message and exit + -o OUTDIR, --outdir OUTDIR + name of directory to create image in + -e IMAGE_NAME, --image-name IMAGE_NAME + name of the image to use the artifacts from e.g. core- + image-sato + -r ROOTFS_DIR, --rootfs-dir ROOTFS_DIR + path to the /rootfs dir to use as the .wks rootfs + source + -b BOOTIMG_DIR, --bootimg-dir BOOTIMG_DIR + path to the dir containing the boot artifacts (e.g. + /EFI or /syslinux dirs) to use as the .wks bootimg + source + -k KERNEL_DIR, --kernel-dir KERNEL_DIR + path to the dir containing the kernel to use in the + .wks bootimg + -n NATIVE_SYSROOT, --native-sysroot NATIVE_SYSROOT + path to the native sysroot containing the tools to use + to build the image + -s, --skip-build-check + skip the build check + -f, --build-rootfs build rootfs + -c {gzip,bzip2,xz}, --compress-with {gzip,bzip2,xz} + compress image with specified compressor + -m, --bmap generate .bmap + --no-fstab-update Do not change fstab file. + -v VARS_DIR, --vars VARS_DIR + directory with <image>.env files that store bitbake + variables + -D, --debug output debug information + +.. note:: + + You do not need root privileges to run Wic. In fact, you should not + run as root when using the utility. + +Cooked Mode +~~~~~~~~~~~ + +Running Wic in cooked mode leverages off artifacts in the Build +Directory. In other words, you do not have to specify kernel or root +filesystem locations as part of the command. All you need to provide is +a kickstart file and the name of the image from which to use artifacts +by using the "-e" option. Wic looks in the Build Directory (e.g. +``tmp/deploy/images/``\ machine) for artifacts. + +The general form of the ``wic`` command using Cooked Mode is as follows: +:: + + $ wic create wks_file -e IMAGE_NAME + + Where: + + wks_file: + An OpenEmbedded kickstart file. You can provide + your own custom file or use a file from a set of + existing files provided with the Yocto Project + release. + + required argument: + -e IMAGE_NAME, --image-name IMAGE_NAME + name of the image to use the artifacts from e.g. core- + image-sato + +Using an Existing Kickstart File +-------------------------------- + +If you do not want to create your own kickstart file, you can use an +existing file provided by the Wic installation. As shipped, kickstart +files can be found in the :ref:`overview-manual/overview-manual-development-environment:yocto project source repositories` in the +following two locations: +:: + + poky/meta-yocto-bsp/wic + poky/scripts/lib/wic/canned-wks + +Use the following command to list the available kickstart files: +:: + + $ wic list images + genericx86 Create an EFI disk image for genericx86* + beaglebone-yocto Create SD card image for Beaglebone + edgerouter Create SD card image for Edgerouter + qemux86-directdisk Create a qemu machine 'pcbios' direct disk image + directdisk-gpt Create a 'pcbios' direct disk image + mkefidisk Create an EFI disk image + directdisk Create a 'pcbios' direct disk image + systemd-bootdisk Create an EFI disk image with systemd-boot + mkhybridiso Create a hybrid ISO image + sdimage-bootpart Create SD card image with a boot partition + directdisk-multi-rootfs Create multi rootfs image using rootfs plugin + directdisk-bootloader-config Create a 'pcbios' direct disk image with custom bootloader config + +When you use an existing file, you +do not have to use the ``.wks`` extension. Here is an example in Raw +Mode that uses the ``directdisk`` file: +:: + + $ wic create directdisk -r rootfs_dir -b bootimg_dir \ + -k kernel_dir -n native_sysroot + +Here are the actual partition language commands used in the +``genericx86.wks`` file to generate an image: +:: + + # short-description: Create an EFI disk image for genericx86* + # long-description: Creates a partitioned EFI disk image for genericx86* machines + part /boot --source bootimg-efi --sourceparams="loader=grub-efi" --ondisk sda --label msdos --active --align 1024 + part / --source rootfs --ondisk sda --fstype=ext4 --label platform --align 1024 --use-uuid + part swap --ondisk sda --size 44 --label swap1 --fstype=swap + + bootloader --ptable gpt --timeout=5 --append="rootfstype=ext4 console=ttyS0,115200 console=tty0" + +Using the Wic Plugin Interface +------------------------------ + +You can extend and specialize Wic functionality by using Wic plugins. +This section explains the Wic plugin interface. + +.. note:: + + Wic plugins consist of "source" and "imager" plugins. Imager plugins + are beyond the scope of this section. + +Source plugins provide a mechanism to customize partition content during +the Wic image generation process. You can use source plugins to map +values that you specify using ``--source`` commands in kickstart files +(i.e. ``*.wks``) to a plugin implementation used to populate a given +partition. + +.. note:: + + If you use plugins that have build-time dependencies (e.g. native + tools, bootloaders, and so forth) when building a Wic image, you need + to specify those dependencies using the :term:`WKS_FILE_DEPENDS` + variable. + +Source plugins are subclasses defined in plugin files. As shipped, the +Yocto Project provides several plugin files. You can see the source +plugin files that ship with the Yocto Project +:yocto_git:`here </poky/tree/scripts/lib/wic/plugins/source>`. +Each of these plugin files contains source plugins that are designed to +populate a specific Wic image partition. + +Source plugins are subclasses of the ``SourcePlugin`` class, which is +defined in the ``poky/scripts/lib/wic/pluginbase.py`` file. For example, +the ``BootimgEFIPlugin`` source plugin found in the ``bootimg-efi.py`` +file is a subclass of the ``SourcePlugin`` class, which is found in the +``pluginbase.py`` file. + +You can also implement source plugins in a layer outside of the Source +Repositories (external layer). To do so, be sure that your plugin files +are located in a directory whose path is +``scripts/lib/wic/plugins/source/`` within your external layer. When the +plugin files are located there, the source plugins they contain are made +available to Wic. + +When the Wic implementation needs to invoke a partition-specific +implementation, it looks for the plugin with the same name as the +``--source`` parameter used in the kickstart file given to that +partition. For example, if the partition is set up using the following +command in a kickstart file: +:: + + part /boot --source bootimg-pcbios --ondisk sda --label boot --active --align 1024 + +The methods defined as class +members of the matching source plugin (i.e. ``bootimg-pcbios``) in the +``bootimg-pcbios.py`` plugin file are used. + +To be more concrete, here is the corresponding plugin definition from +the ``bootimg-pcbios.py`` file for the previous command along with an +example method called by the Wic implementation when it needs to prepare +a partition using an implementation-specific function: +:: + + . + . + . + class BootimgPcbiosPlugin(SourcePlugin): + """ + Create MBR boot partition and install syslinux on it. + """ + + name = 'bootimg-pcbios' + . + . + . + @classmethod + def do_prepare_partition(cls, part, source_params, creator, cr_workdir, + oe_builddir, bootimg_dir, kernel_dir, + rootfs_dir, native_sysroot): + """ + Called to do the actual content population for a partition i.e. it + 'prepares' the partition to be incorporated into the image. + In this case, prepare content for legacy bios boot partition. + """ + . + . + . + +If a +subclass (plugin) itself does not implement a particular function, Wic +locates and uses the default version in the superclass. It is for this +reason that all source plugins are derived from the ``SourcePlugin`` +class. + +The ``SourcePlugin`` class defined in the ``pluginbase.py`` file defines +a set of methods that source plugins can implement or override. Any +plugins (subclass of ``SourcePlugin``) that do not implement a +particular method inherit the implementation of the method from the +``SourcePlugin`` class. For more information, see the ``SourcePlugin`` +class in the ``pluginbase.py`` file for details: + +The following list describes the methods implemented in the +``SourcePlugin`` class: + +- ``do_prepare_partition()``: Called to populate a partition with + actual content. In other words, the method prepares the final + partition image that is incorporated into the disk image. + +- ``do_configure_partition()``: Called before + ``do_prepare_partition()`` to create custom configuration files for a + partition (e.g. syslinux or grub configuration files). + +- ``do_install_disk()``: Called after all partitions have been + prepared and assembled into a disk image. This method provides a hook + to allow finalization of a disk image (e.g. writing an MBR). + +- ``do_stage_partition()``: Special content-staging hook called + before ``do_prepare_partition()``. This method is normally empty. + + Typically, a partition just uses the passed-in parameters (e.g. the + unmodified value of ``bootimg_dir``). However, in some cases, things + might need to be more tailored. As an example, certain files might + additionally need to be taken from ``bootimg_dir + /boot``. This hook + allows those files to be staged in a customized fashion. + + .. note:: + + ``get_bitbake_var()`` allows you to access non-standard variables that + you might want to use for this behavior. + +You can extend the source plugin mechanism. To add more hooks, create +more source plugin methods within ``SourcePlugin`` and the corresponding +derived subclasses. The code that calls the plugin methods uses the +``plugin.get_source_plugin_methods()`` function to find the method or +methods needed by the call. Retrieval of those methods is accomplished +by filling up a dict with keys that contain the method names of +interest. On success, these will be filled in with the actual methods. +See the Wic implementation for examples and details. + +Wic Examples +------------ + +This section provides several examples that show how to use the Wic +utility. All the examples assume the list of requirements in the +"`Requirements <#wic-requirements>`__" section have been met. The +examples assume the previously generated image is +``core-image-minimal``. + +Generate an Image using an Existing Kickstart File +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This example runs in Cooked Mode and uses the ``mkefidisk`` kickstart +file: +:: + + $ wic create mkefidisk -e core-image-minimal + INFO: Building wic-tools... + . + . + . + INFO: The new image(s) can be found here: + ./mkefidisk-201804191017-sda.direct + + The following build artifacts were used to create the image(s): + ROOTFS_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs + BOOTIMG_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share + KERNEL_DIR: /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86 + NATIVE_SYSROOT: /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native + + INFO: The image(s) were created using OE kickstart file: + /home/stephano/build/master/openembedded-core/scripts/lib/wic/canned-wks/mkefidisk.wks + +The previous example shows the easiest way to create an image by running +in cooked mode and supplying a kickstart file and the "-e" option to +point to the existing build artifacts. Your ``local.conf`` file needs to +have the :term:`MACHINE` variable set +to the machine you are using, which is "qemux86" in this example. + +Once the image builds, the output provides image location, artifact use, +and kickstart file information. + +.. note:: + + You should always verify the details provided in the output to make + sure that the image was indeed created exactly as expected. + +Continuing with the example, you can now write the image from the Build +Directory onto a USB stick, or whatever media for which you built your +image, and boot from the media. You can write the image by using +``bmaptool`` or ``dd``: +:: + + $ oe-run-native bmaptool copy mkefidisk-201804191017-sda.direct /dev/sdX + +or :: + + $ sudo dd if=mkefidisk-201804191017-sda.direct of=/dev/sdX + +.. note:: + + For more information on how to use the ``bmaptool`` + to flash a device with an image, see the + ":ref:`dev-manual/common-tasks:flashing images using \`\`bmaptool\`\``" + section. + +Using a Modified Kickstart File +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Because partitioned image creation is driven by the kickstart file, it +is easy to affect image creation by changing the parameters in the file. +This next example demonstrates that through modification of the +``directdisk-gpt`` kickstart file. + +As mentioned earlier, you can use the command ``wic list images`` to +show the list of existing kickstart files. The directory in which the +``directdisk-gpt.wks`` file resides is +``scripts/lib/image/canned-wks/``, which is located in the +:term:`Source Directory` (e.g. ``poky``). +Because available files reside in this directory, you can create and add +your own custom files to the directory. Subsequent use of the +``wic list images`` command would then include your kickstart files. + +In this example, the existing ``directdisk-gpt`` file already does most +of what is needed. However, for the hardware in this example, the image +will need to boot from ``sdb`` instead of ``sda``, which is what the +``directdisk-gpt`` kickstart file uses. + +The example begins by making a copy of the ``directdisk-gpt.wks`` file +in the ``scripts/lib/image/canned-wks`` directory and then by changing +the lines that specify the target disk from which to boot. +:: + + $ cp /home/stephano/poky/scripts/lib/wic/canned-wks/directdisk-gpt.wks \ + /home/stephano/poky/scripts/lib/wic/canned-wks/directdisksdb-gpt.wks + +Next, the example modifies the ``directdisksdb-gpt.wks`` file and +changes all instances of "``--ondisk sda``" to "``--ondisk sdb``". The +example changes the following two lines and leaves the remaining lines +untouched: +:: + + part /boot --source bootimg-pcbios --ondisk sdb --label boot --active --align 1024 + part / --source rootfs --ondisk sdb --fstype=ext4 --label platform --align 1024 --use-uuid + +Once the lines are changed, the +example generates the ``directdisksdb-gpt`` image. The command points +the process at the ``core-image-minimal`` artifacts for the Next Unit of +Computing (nuc) :term:`MACHINE` the +``local.conf``. +:: + + $ wic create directdisksdb-gpt -e core-image-minimal + INFO: Building wic-tools... + . + . + . + Initialising tasks: 100% |#######################################| Time: 0:00:01 + NOTE: Executing SetScene Tasks + NOTE: Executing RunQueue Tasks + NOTE: Tasks Summary: Attempted 1161 tasks of which 1157 didn't need to be rerun and all succeeded. + INFO: Creating image(s)... + + INFO: The new image(s) can be found here: + ./directdisksdb-gpt-201710090938-sdb.direct + + The following build artifacts were used to create the image(s): + ROOTFS_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs + BOOTIMG_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share + KERNEL_DIR: /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86 + NATIVE_SYSROOT: /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native + + INFO: The image(s) were created using OE kickstart file: + /home/stephano/poky/scripts/lib/wic/canned-wks/directdisksdb-gpt.wks + +Continuing with the example, you can now directly ``dd`` the image to a +USB stick, or whatever media for which you built your image, and boot +the resulting media: +:: + + $ sudo dd if=directdisksdb-gpt-201710090938-sdb.direct of=/dev/sdb + 140966+0 records in + 140966+0 records out + 72174592 bytes (72 MB, 69 MiB) copied, 78.0282 s, 925 kB/s + $ sudo eject /dev/sdb + +Using a Modified Kickstart File and Running in Raw Mode +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This next example manually specifies each build artifact (runs in Raw +Mode) and uses a modified kickstart file. The example also uses the +``-o`` option to cause Wic to create the output somewhere other than the +default output directory, which is the current directory: +:: + + $ wic create /home/stephano/my_yocto/test.wks -o /home/stephano/testwic \ + --rootfs-dir /home/stephano/build/master/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/rootfs \ + --bootimg-dir /home/stephano/build/master/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share \ + --kernel-dir /home/stephano/build/master/build/tmp/deploy/images/qemux86 \ + --native-sysroot /home/stephano/build/master/build/tmp/work/i586-poky-linux/wic-tools/1.0-r0/recipe-sysroot-native + + INFO: Creating image(s)... + + INFO: The new image(s) can be found here: + /home/stephano/testwic/test-201710091445-sdb.direct + + The following build artifacts were used to create the image(s): + ROOTFS_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs + BOOTIMG_DIR: /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share + KERNEL_DIR: /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86 + NATIVE_SYSROOT: /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native + + INFO: The image(s) were created using OE kickstart file: + /home/stephano/my_yocto/test.wks + +For this example, +:term:`MACHINE` did not have to be +specified in the ``local.conf`` file since the artifact is manually +specified. + +Using Wic to Manipulate an Image +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Wic image manipulation allows you to shorten turnaround time during +image development. For example, you can use Wic to delete the kernel +partition of a Wic image and then insert a newly built kernel. This +saves you time from having to rebuild the entire image each time you +modify the kernel. + +.. note:: + + In order to use Wic to manipulate a Wic image as in this example, + your development machine must have the ``mtools`` package installed. + +The following example examines the contents of the Wic image, deletes +the existing kernel, and then inserts a new kernel: + +1. *List the Partitions:* Use the ``wic ls`` command to list all the + partitions in the Wic image: + :: + + $ wic ls tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic + Num Start End Size Fstype + 1 1048576 25041919 23993344 fat16 + 2 25165824 72157183 46991360 ext4 + + The previous output shows two partitions in the + ``core-image-minimal-qemux86.wic`` image. + +2. *Examine a Particular Partition:* Use the ``wic ls`` command again + but in a different form to examine a particular partition. + + .. note:: + + You can get command usage on any Wic command using the following + form: + :: + + $ wic help command + + + For example, the following command shows you the various ways to + use the + wic ls + command: + :: + + $ wic help ls + + + The following command shows what is in Partition one: + :: + + $ wic ls tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1 + Volume in drive : is boot + Volume Serial Number is E894-1809 + Directory for ::/ + + libcom32 c32 186500 2017-10-09 16:06 + libutil c32 24148 2017-10-09 16:06 + syslinux cfg 220 2017-10-09 16:06 + vesamenu c32 27104 2017-10-09 16:06 + vmlinuz 6904608 2017-10-09 16:06 + 5 files 7 142 580 bytes + 16 582 656 bytes free + + The previous output shows five files, with the + ``vmlinuz`` being the kernel. + + .. note:: + + If you see the following error, you need to update or create a + ``~/.mtoolsrc`` file and be sure to have the line "mtools_skip_check=1" + in the file. Then, run the Wic command again: + :: + + ERROR: _exec_cmd: /usr/bin/mdir -i /tmp/wic-parttfokuwra ::/ returned '1' instead of 0 + output: Total number of sectors (47824) not a multiple of sectors per track (32)! + Add mtools_skip_check=1 to your .mtoolsrc file to skip this test + + +3. *Remove the Old Kernel:* Use the ``wic rm`` command to remove the + ``vmlinuz`` file (kernel): + :: + + $ wic rm tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1/vmlinuz + +4. *Add In the New Kernel:* Use the ``wic cp`` command to add the + updated kernel to the Wic image. Depending on how you built your + kernel, it could be in different places. If you used ``devtool`` and + an SDK to build your kernel, it resides in the ``tmp/work`` directory + of the extensible SDK. If you used ``make`` to build the kernel, the + kernel will be in the ``workspace/sources`` area. + + The following example assumes ``devtool`` was used to build the + kernel: + :: + + cp ~/poky_sdk/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+git999-r0/linux-yocto-4.12.12+git999/arch/x86/boot/bzImage \ + ~/poky/build/tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1/vmlinuz + + Once the new kernel is added back into the image, you can use the + ``dd`` command or :ref:`bmaptool + <dev-manual/common-tasks:flashing images using \`\`bmaptool\`\`>` + to flash your wic image onto an SD card or USB stick and test your + target. + + .. note:: + + Using ``bmaptool`` is generally 10 to 20 times faster than using ``dd``. + +Flashing Images Using ``bmaptool`` +================================== + +A fast and easy way to flash an image to a bootable device is to use +Bmaptool, which is integrated into the OpenEmbedded build system. +Bmaptool is a generic tool that creates a file's block map (bmap) and +then uses that map to copy the file. As compared to traditional tools +such as dd or cp, Bmaptool can copy (or flash) large files like raw +system image files much faster. + +.. note:: + + - If you are using Ubuntu or Debian distributions, you can install + the ``bmap-tools`` package using the following command and then + use the tool without specifying ``PATH`` even from the root + account: + :: + + $ sudo apt-get install bmap-tools + + - If you are unable to install the ``bmap-tools`` package, you will + need to build Bmaptool before using it. Use the following command: + :: + + $ bitbake bmap-tools-native + +Following, is an example that shows how to flash a Wic image. Realize +that while this example uses a Wic image, you can use Bmaptool to flash +any type of image. Use these steps to flash an image using Bmaptool: + +1. *Update your local.conf File:* You need to have the following set + in your ``local.conf`` file before building your image: + :: + + IMAGE_FSTYPES += "wic wic.bmap" + +2. *Get Your Image:* Either have your image ready (pre-built with the + :term:`IMAGE_FSTYPES` + setting previously mentioned) or take the step to build the image: + :: + + $ bitbake image + +3. *Flash the Device:* Flash the device with the image by using Bmaptool + depending on your particular setup. The following commands assume the + image resides in the Build Directory's ``deploy/images/`` area: + + - If you have write access to the media, use this command form: + :: + + $ oe-run-native bmap-tools-native bmaptool copy build-directory/tmp/deploy/images/machine/image.wic /dev/sdX + + - If you do not have write access to the media, set your permissions + first and then use the same command form: + :: + + $ sudo chmod 666 /dev/sdX + $ oe-run-native bmap-tools-native bmaptool copy build-directory/tmp/deploy/images/machine/image.wic /dev/sdX + +For help on the ``bmaptool`` command, use the following command: +:: + + $ bmaptool --help + +Making Images More Secure +========================= + +Security is of increasing concern for embedded devices. Consider the +issues and problems discussed in just this sampling of work found across +the Internet: + +- *"*\ `Security Risks of Embedded + Systems <https://www.schneier.com/blog/archives/2014/01/security_risks_9.html>`__\ *"* + by Bruce Schneier + +- *"*\ `Internet Census + 2012 <http://census2012.sourceforge.net/paper.html>`__\ *"* by Carna + Botnet + +- *"*\ `Security Issues for Embedded + Devices <http://elinux.org/images/6/6f/Security-issues.pdf>`__\ *"* + by Jake Edge + +When securing your image is of concern, there are steps, tools, and +variables that you can consider to help you reach the security goals you +need for your particular device. Not all situations are identical when +it comes to making an image secure. Consequently, this section provides +some guidance and suggestions for consideration when you want to make +your image more secure. + +.. note:: + + Because the security requirements and risks are different for every + type of device, this section cannot provide a complete reference on + securing your custom OS. It is strongly recommended that you also + consult other sources of information on embedded Linux system + hardening and on security. + +General Considerations +---------------------- + +General considerations exist that help you create more secure images. +You should consider the following suggestions to help make your device +more secure: + +- Scan additional code you are adding to the system (e.g. application + code) by using static analysis tools. Look for buffer overflows and + other potential security problems. + +- Pay particular attention to the security for any web-based + administration interface. + + Web interfaces typically need to perform administrative functions and + tend to need to run with elevated privileges. Thus, the consequences + resulting from the interface's security becoming compromised can be + serious. Look for common web vulnerabilities such as + cross-site-scripting (XSS), unvalidated inputs, and so forth. + + As with system passwords, the default credentials for accessing a + web-based interface should not be the same across all devices. This + is particularly true if the interface is enabled by default as it can + be assumed that many end-users will not change the credentials. + +- Ensure you can update the software on the device to mitigate + vulnerabilities discovered in the future. This consideration + especially applies when your device is network-enabled. + +- Ensure you remove or disable debugging functionality before producing + the final image. For information on how to do this, see the + "`Considerations Specific to the OpenEmbedded Build + System <#considerations-specific-to-the-openembedded-build-system>`__" + section. + +- Ensure you have no network services listening that are not needed. + +- Remove any software from the image that is not needed. + +- Enable hardware support for secure boot functionality when your + device supports this functionality. + +Security Flags +-------------- + +The Yocto Project has security flags that you can enable that help make +your build output more secure. The security flags are in the +``meta/conf/distro/include/security_flags.inc`` file in your +:term:`Source Directory` (e.g. ``poky``). + +.. note:: + + Depending on the recipe, certain security flags are enabled and + disabled by default. + +Use the following line in your ``local.conf`` file or in your custom +distribution configuration file to enable the security compiler and +linker flags for your build: +:: + + require conf/distro/include/security_flags.inc + +Considerations Specific to the OpenEmbedded Build System +-------------------------------------------------------- + +You can take some steps that are specific to the OpenEmbedded build +system to make your images more secure: + +- Ensure "debug-tweaks" is not one of your selected + :term:`IMAGE_FEATURES`. + When creating a new project, the default is to provide you with an + initial ``local.conf`` file that enables this feature using the + :term:`EXTRA_IMAGE_FEATURES` + variable with the line: + :: + + EXTRA_IMAGE_FEATURES = "debug-tweaks" + + To disable that feature, simply comment out that line in your + ``local.conf`` file, or make sure ``IMAGE_FEATURES`` does not contain + "debug-tweaks" before producing your final image. Among other things, + leaving this in place sets the root password as blank, which makes + logging in for debugging or inspection easy during development but + also means anyone can easily log in during production. + +- It is possible to set a root password for the image and also to set + passwords for any extra users you might add (e.g. administrative or + service type users). When you set up passwords for multiple images or + users, you should not duplicate passwords. + + To set up passwords, use the + :ref:`extrausers <ref-classes-extrausers>` + class, which is the preferred method. For an example on how to set up + both root and user passwords, see the + ":ref:`extrausers.bbclass <ref-classes-extrausers>`" + section. + + .. note:: + + When adding extra user accounts or setting a root password, be + cautious about setting the same password on every device. If you + do this, and the password you have set is exposed, then every + device is now potentially compromised. If you need this access but + want to ensure security, consider setting a different, random + password for each device. Typically, you do this as a separate + step after you deploy the image onto the device. + +- Consider enabling a Mandatory Access Control (MAC) framework such as + SMACK or SELinux and tuning it appropriately for your device's usage. + You can find more information in the + :yocto_git:`meta-selinux </meta-selinux/>` layer. + +Tools for Hardening Your Image +------------------------------ + +The Yocto Project provides tools for making your image more secure. You +can find these tools in the ``meta-security`` layer of the +:yocto_git:`Yocto Project Source Repositories <>`. + +Creating Your Own Distribution +============================== + +When you build an image using the Yocto Project and do not alter any +distribution :term:`Metadata`, you are +creating a Poky distribution. If you wish to gain more control over +package alternative selections, compile-time options, and other +low-level configurations, you can create your own distribution. + +To create your own distribution, the basic steps consist of creating +your own distribution layer, creating your own distribution +configuration file, and then adding any needed code and Metadata to the +layer. The following steps provide some more detail: + +- *Create a layer for your new distro:* Create your distribution layer + so that you can keep your Metadata and code for the distribution + separate. It is strongly recommended that you create and use your own + layer for configuration and code. Using your own layer as compared to + just placing configurations in a ``local.conf`` configuration file + makes it easier to reproduce the same build configuration when using + multiple build machines. See the + ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`" + section for information on how to quickly set up a layer. + +- *Create the distribution configuration file:* The distribution + configuration file needs to be created in the ``conf/distro`` + directory of your layer. You need to name it using your distribution + name (e.g. ``mydistro.conf``). + + .. note:: + + The :term:`DISTRO` variable in your ``local.conf`` file determines the + name of your distribution. + + You can split out parts of your configuration file into include files + and then "require" them from within your distribution configuration + file. Be sure to place the include files in the + ``conf/distro/include`` directory of your layer. A common example + usage of include files would be to separate out the selection of + desired version and revisions for individual recipes. + + Your configuration file needs to set the following required + variables: + + - :term:`DISTRO_NAME` + + - :term:`DISTRO_VERSION` + + These following variables are optional and you typically set them + from the distribution configuration file: + + - :term:`DISTRO_FEATURES` + + - :term:`DISTRO_EXTRA_RDEPENDS` + + - :term:`DISTRO_EXTRA_RRECOMMENDS` + + - :term:`TCLIBC` + + .. tip:: + + If you want to base your distribution configuration file on the + very basic configuration from OE-Core, you can use + ``conf/distro/defaultsetup.conf`` as a reference and just include + variables that differ as compared to ``defaultsetup.conf``. + Alternatively, you can create a distribution configuration file + from scratch using the ``defaultsetup.conf`` file or configuration files + from other distributions such as Poky or Angstrom as references. + +- *Provide miscellaneous variables:* Be sure to define any other + variables for which you want to create a default or enforce as part + of the distribution configuration. You can include nearly any + variable from the ``local.conf`` file. The variables you use are not + limited to the list in the previous bulleted item. + +- *Point to Your distribution configuration file:* In your + ``local.conf`` file in the :term:`Build Directory`, + set your + :term:`DISTRO` variable to point to + your distribution's configuration file. For example, if your + distribution's configuration file is named ``mydistro.conf``, then + you point to it as follows: + :: + + DISTRO = "mydistro" + +- *Add more to the layer if necessary:* Use your layer to hold other + information needed for the distribution: + + - Add recipes for installing distro-specific configuration files + that are not already installed by another recipe. If you have + distro-specific configuration files that are included by an + existing recipe, you should add an append file (``.bbappend``) for + those. For general information and recommendations on how to add + recipes to your layer, see the "`Creating Your Own + Layer <#creating-your-own-layer>`__" and "`Following Best + Practices When Creating + Layers <#best-practices-to-follow-when-creating-layers>`__" + sections. + + - Add any image recipes that are specific to your distribution. + + - Add a ``psplash`` append file for a branded splash screen. For + information on append files, see the "`Using .bbappend Files in + Your Layer <#using-bbappend-files>`__" section. + + - Add any other append files to make custom changes that are + specific to individual recipes. + +Creating a Custom Template Configuration Directory +================================================== + +If you are producing your own customized version of the build system for +use by other users, you might want to customize the message shown by the +setup script or you might want to change the template configuration +files (i.e. ``local.conf`` and ``bblayers.conf``) that are created in a +new build directory. + +The OpenEmbedded build system uses the environment variable +``TEMPLATECONF`` to locate the directory from which it gathers +configuration information that ultimately ends up in the +:term:`Build Directory` ``conf`` directory. +By default, ``TEMPLATECONF`` is set as follows in the ``poky`` +repository: +:: + + TEMPLATECONF=${TEMPLATECONF:-meta-poky/conf} + +This is the +directory used by the build system to find templates from which to build +some key configuration files. If you look at this directory, you will +see the ``bblayers.conf.sample``, ``local.conf.sample``, and +``conf-notes.txt`` files. The build system uses these files to form the +respective ``bblayers.conf`` file, ``local.conf`` file, and display the +list of BitBake targets when running the setup script. + +To override these default configuration files with configurations you +want used within every new Build Directory, simply set the +``TEMPLATECONF`` variable to your directory. The ``TEMPLATECONF`` +variable is set in the ``.templateconf`` file, which is in the top-level +:term:`Source Directory` folder +(e.g. ``poky``). Edit the ``.templateconf`` so that it can locate your +directory. + +Best practices dictate that you should keep your template configuration +directory in your custom distribution layer. For example, suppose you +have a layer named ``meta-mylayer`` located in your home directory and +you want your template configuration directory named ``myconf``. +Changing the ``.templateconf`` as follows causes the OpenEmbedded build +system to look in your directory and base its configuration files on the +``*.sample`` configuration files it finds. The final configuration files +(i.e. ``local.conf`` and ``bblayers.conf`` ultimately still end up in +your Build Directory, but they are based on your ``*.sample`` files. +:: + + TEMPLATECONF=${TEMPLATECONF:-meta-mylayer/myconf} + +Aside from the ``*.sample`` configuration files, the ``conf-notes.txt`` +also resides in the default ``meta-poky/conf`` directory. The script +that sets up the build environment (i.e. +:ref:`structure-core-script`) uses this file to +display BitBake targets as part of the script output. Customizing this +``conf-notes.txt`` file is a good way to make sure your list of custom +targets appears as part of the script's output. + +Here is the default list of targets displayed as a result of running +either of the setup scripts: +:: + + You can now run 'bitbake <target>' + + Common targets are: + core-image-minimal + core-image-sato + meta-toolchain + meta-ide-support + +Changing the listed common targets is as easy as editing your version of +``conf-notes.txt`` in your custom template configuration directory and +making sure you have ``TEMPLATECONF`` set to your directory. + +Conserving Disk Space During Builds +=================================== + +To help conserve disk space during builds, you can add the following +statement to your project's ``local.conf`` configuration file found in +the :term:`Build Directory`: +:: + + INHERIT += "rm_work" + +Adding this statement deletes the work directory used for +building a recipe once the recipe is built. For more information on +"rm_work", see the +:ref:`rm_work <ref-classes-rm-work>` class in the +Yocto Project Reference Manual. + +Working with Packages +===================== + +This section describes a few tasks that involve packages: + +- `Excluding packages from an + image <#excluding-packages-from-an-image>`__ + +- `Incrementing a binary package + version <#incrementing-a-binary-package-version>`__ + +- `Handling optional module + packaging <#handling-optional-module-packaging>`__ + +- `Using runtime package + management <#using-runtime-package-management>`__ + +- `Generating and using signed + packages <#generating-and-using-signed-packages>`__ + +- `Setting up and running package test + (ptest) <#testing-packages-with-ptest>`__ + +- `Creating node package manager (NPM) + packages <#creating-node-package-manager-npm-packages>`__ + +- `Adding custom metadata to + packages <#adding-custom-metadata-to-packages>`__ + +Excluding Packages from an Image +-------------------------------- + +You might find it necessary to prevent specific packages from being +installed into an image. If so, you can use several variables to direct +the build system to essentially ignore installing recommended packages +or to not install a package at all. + +The following list introduces variables you can use to prevent packages +from being installed into your image. Each of these variables only works +with IPK and RPM package types. Support for Debian packages does not +exist. Also, you can use these variables from your ``local.conf`` file +or attach them to a specific image recipe by using a recipe name +override. For more detail on the variables, see the descriptions in the +Yocto Project Reference Manual's glossary chapter. + +- :term:`BAD_RECOMMENDATIONS`: + Use this variable to specify "recommended-only" packages that you do + not want installed. + +- :term:`NO_RECOMMENDATIONS`: + Use this variable to prevent all "recommended-only" packages from + being installed. + +- :term:`PACKAGE_EXCLUDE`: + Use this variable to prevent specific packages from being installed + regardless of whether they are "recommended-only" or not. You need to + realize that the build process could fail with an error when you + prevent the installation of a package whose presence is required by + an installed package. + +Incrementing a Package Version +------------------------------ + +This section provides some background on how binary package versioning +is accomplished and presents some of the services, variables, and +terminology involved. + +In order to understand binary package versioning, you need to consider +the following: + +- Binary Package: The binary package that is eventually built and + installed into an image. + +- Binary Package Version: The binary package version is composed of two + components - a version and a revision. + + .. note:: + + Technically, a third component, the "epoch" (i.e. :term:`PE`) is involved + but this discussion for the most part ignores ``PE``. + + The version and revision are taken from the + :term:`PV` and + :term:`PR` variables, respectively. + +- ``PV``: The recipe version. ``PV`` represents the version of the + software being packaged. Do not confuse ``PV`` with the binary + package version. + +- ``PR``: The recipe revision. + +- :term:`SRCPV`: The OpenEmbedded + build system uses this string to help define the value of ``PV`` when + the source code revision needs to be included in it. + +- :yocto_wiki:`PR Service </PR_Service>`: A + network-based service that helps automate keeping package feeds + compatible with existing package manager applications such as RPM, + APT, and OPKG. + +Whenever the binary package content changes, the binary package version +must change. Changing the binary package version is accomplished by +changing or "bumping" the ``PR`` and/or ``PV`` values. Increasing these +values occurs one of two ways: + +- Automatically using a Package Revision Service (PR Service). + +- Manually incrementing the ``PR`` and/or ``PV`` variables. + +Given a primary challenge of any build system and its users is how to +maintain a package feed that is compatible with existing package manager +applications such as RPM, APT, and OPKG, using an automated system is +much preferred over a manual system. In either system, the main +requirement is that binary package version numbering increases in a +linear fashion and that a number of version components exist that +support that linear progression. For information on how to ensure +package revisioning remains linear, see the "`Automatically Incrementing +a Binary Package Revision +Number <#automatically-incrementing-a-binary-package-revision-number>`__" +section. + +The following three sections provide related information on the PR +Service, the manual method for "bumping" ``PR`` and/or ``PV``, and on +how to ensure binary package revisioning remains linear. + +Working With a PR Service +~~~~~~~~~~~~~~~~~~~~~~~~~ + +As mentioned, attempting to maintain revision numbers in the +:term:`Metadata` is error prone, inaccurate, +and causes problems for people submitting recipes. Conversely, the PR +Service automatically generates increasing numbers, particularly the +revision field, which removes the human element. + +.. note:: + + For additional information on using a PR Service, you can see the + :yocto_wiki:`PR Service </PR_Service>` wiki page. + +The Yocto Project uses variables in order of decreasing priority to +facilitate revision numbering (i.e. +:term:`PE`, +:term:`PV`, and +:term:`PR` for epoch, version, and +revision, respectively). The values are highly dependent on the policies +and procedures of a given distribution and package feed. + +Because the OpenEmbedded build system uses +":ref:`signatures <overview-manual/overview-manual-concepts:checksums (signatures)>`", which are +unique to a given build, the build system knows when to rebuild +packages. All the inputs into a given task are represented by a +signature, which can trigger a rebuild when different. Thus, the build +system itself does not rely on the ``PR``, ``PV``, and ``PE`` numbers to +trigger a rebuild. The signatures, however, can be used to generate +these values. + +The PR Service works with both ``OEBasic`` and ``OEBasicHash`` +generators. The value of ``PR`` bumps when the checksum changes and the +different generator mechanisms change signatures under different +circumstances. + +As implemented, the build system includes values from the PR Service +into the ``PR`` field as an addition using the form "``.x``" so ``r0`` +becomes ``r0.1``, ``r0.2`` and so forth. This scheme allows existing +``PR`` values to be used for whatever reasons, which include manual +``PR`` bumps, should it be necessary. + +By default, the PR Service is not enabled or running. Thus, the packages +generated are just "self consistent". The build system adds and removes +packages and there are no guarantees about upgrade paths but images will +be consistent and correct with the latest changes. + +The simplest form for a PR Service is for it to exist for a single host +development system that builds the package feed (building system). For +this scenario, you can enable a local PR Service by setting +:term:`PRSERV_HOST` in your +``local.conf`` file in the :term:`Build Directory`: +:: + + PRSERV_HOST = "localhost:0" + +Once the service is started, packages will automatically +get increasing ``PR`` values and BitBake takes care of starting and +stopping the server. + +If you have a more complex setup where multiple host development systems +work against a common, shared package feed, you have a single PR Service +running and it is connected to each building system. For this scenario, +you need to start the PR Service using the ``bitbake-prserv`` command: +:: + + bitbake-prserv --host ip --port port --start + +In addition to +hand-starting the service, you need to update the ``local.conf`` file of +each building system as described earlier so each system points to the +server and port. + +It is also recommended you use build history, which adds some sanity +checks to binary package versions, in conjunction with the server that +is running the PR Service. To enable build history, add the following to +each building system's ``local.conf`` file: +:: + + # It is recommended to activate "buildhistory" for testing the PR service + INHERIT += "buildhistory" + BUILDHISTORY_COMMIT = "1" + +For information on build +history, see the "`Maintaining Build Output +Quality <#maintaining-build-output-quality>`__" section. + +.. note:: + + The OpenEmbedded build system does not maintain ``PR`` information as + part of the shared state (sstate) packages. If you maintain an sstate + feed, its expected that either all your building systems that + contribute to the sstate feed use a shared PR Service, or you do not + run a PR Service on any of your building systems. Having some systems + use a PR Service while others do not leads to obvious problems. + + For more information on shared state, see the + ":ref:`overview-manual/overview-manual-concepts:shared state cache`" + section in the Yocto Project Overview and Concepts Manual. + +Manually Bumping PR +~~~~~~~~~~~~~~~~~~~ + +The alternative to setting up a PR Service is to manually "bump" the +:term:`PR` variable. + +If a committed change results in changing the package output, then the +value of the PR variable needs to be increased (or "bumped") as part of +that commit. For new recipes you should add the ``PR`` variable and set +its initial value equal to "r0", which is the default. Even though the +default value is "r0", the practice of adding it to a new recipe makes +it harder to forget to bump the variable when you make changes to the +recipe in future. + +If you are sharing a common ``.inc`` file with multiple recipes, you can +also use the ``INC_PR`` variable to ensure that the recipes sharing the +``.inc`` file are rebuilt when the ``.inc`` file itself is changed. The +``.inc`` file must set ``INC_PR`` (initially to "r0"), and all recipes +referring to it should set ``PR`` to "${INC_PR}.0" initially, +incrementing the last number when the recipe is changed. If the ``.inc`` +file is changed then its ``INC_PR`` should be incremented. + +When upgrading the version of a binary package, assuming the ``PV`` +changes, the ``PR`` variable should be reset to "r0" (or "${INC_PR}.0" +if you are using ``INC_PR``). + +Usually, version increases occur only to binary packages. However, if +for some reason ``PV`` changes but does not increase, you can increase +the ``PE`` variable (Package Epoch). The ``PE`` variable defaults to +"0". + +Binary package version numbering strives to follow the `Debian Version +Field Policy +Guidelines <https://www.debian.org/doc/debian-policy/ch-controlfields.html>`__. +These guidelines define how versions are compared and what "increasing" +a version means. + +Automatically Incrementing a Package Version Number +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When fetching a repository, BitBake uses the +:term:`SRCREV` variable to determine +the specific source code revision from which to build. You set the +``SRCREV`` variable to +:term:`AUTOREV` to cause the +OpenEmbedded build system to automatically use the latest revision of +the software: +:: + + SRCREV = "${AUTOREV}" + +Furthermore, you need to reference ``SRCPV`` in ``PV`` in order to +automatically update the version whenever the revision of the source +code changes. Here is an example: +:: + + PV = "1.0+git${SRCPV}" + +The OpenEmbedded build system substitutes ``SRCPV`` with the following: + +.. code-block:: none + + AUTOINC+source_code_revision + +The build system replaces the ``AUTOINC`` +with a number. The number used depends on the state of the PR Service: + +- If PR Service is enabled, the build system increments the number, + which is similar to the behavior of + :term:`PR`. This behavior results in + linearly increasing package versions, which is desirable. Here is an + example: + + .. code-block:: none + + hello-world-git_0.0+git0+b6558dd387-r0.0_armv7a-neon.ipk + hello-world-git_0.0+git1+dd2f5c3565-r0.0_armv7a-neon.ipk + +- If PR Service is not enabled, the build system replaces the + ``AUTOINC`` placeholder with zero (i.e. "0"). This results in + changing the package version since the source revision is included. + However, package versions are not increased linearly. Here is an + example: + + .. code-block:: none + + hello-world-git_0.0+git0+b6558dd387-r0.0_armv7a-neon.ipk + hello-world-git_0.0+git0+dd2f5c3565-r0.0_armv7a-neon.ipk + +In summary, the OpenEmbedded build system does not track the history of +binary package versions for this purpose. ``AUTOINC``, in this case, is +comparable to ``PR``. If PR server is not enabled, ``AUTOINC`` in the +package version is simply replaced by "0". If PR server is enabled, the +build system keeps track of the package versions and bumps the number +when the package revision changes. + +Handling Optional Module Packaging +---------------------------------- + +Many pieces of software split functionality into optional modules (or +plugins) and the plugins that are built might depend on configuration +options. To avoid having to duplicate the logic that determines what +modules are available in your recipe or to avoid having to package each +module by hand, the OpenEmbedded build system provides functionality to +handle module packaging dynamically. + +To handle optional module packaging, you need to do two things: + +- Ensure the module packaging is actually done. + +- Ensure that any dependencies on optional modules from other recipes + are satisfied by your recipe. + +Making Sure the Packaging is Done +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To ensure the module packaging actually gets done, you use the +``do_split_packages`` function within the ``populate_packages`` Python +function in your recipe. The ``do_split_packages`` function searches for +a pattern of files or directories under a specified path and creates a +package for each one it finds by appending to the +:term:`PACKAGES` variable and +setting the appropriate values for ``FILES_packagename``, +``RDEPENDS_packagename``, ``DESCRIPTION_packagename``, and so forth. +Here is an example from the ``lighttpd`` recipe: +:: + + python populate_packages_prepend () { + lighttpd_libdir = d.expand('${libdir}') + do_split_packages(d, lighttpd_libdir, '^mod_(.*).so$', + 'lighttpd-module-%s', 'Lighttpd module for %s', + extra_depends='') + } + +The previous example specifies a number of things in the call to +``do_split_packages``. + +- A directory within the files installed by your recipe through + ``do_install`` in which to search. + +- A regular expression used to match module files in that directory. In + the example, note the parentheses () that mark the part of the + expression from which the module name should be derived. + +- A pattern to use for the package names. + +- A description for each package. + +- An empty string for ``extra_depends``, which disables the default + dependency on the main ``lighttpd`` package. Thus, if a file in + ``${libdir}`` called ``mod_alias.so`` is found, a package called + ``lighttpd-module-alias`` is created for it and the + :term:`DESCRIPTION` is set to + "Lighttpd module for alias". + +Often, packaging modules is as simple as the previous example. However, +more advanced options exist that you can use within +``do_split_packages`` to modify its behavior. And, if you need to, you +can add more logic by specifying a hook function that is called for each +package. It is also perfectly acceptable to call ``do_split_packages`` +multiple times if you have more than one set of modules to package. + +For more examples that show how to use ``do_split_packages``, see the +``connman.inc`` file in the ``meta/recipes-connectivity/connman/`` +directory of the ``poky`` :ref:`source repository <overview-manual/overview-manual-development-environment:yocto project source repositories>`. You can +also find examples in ``meta/classes/kernel.bbclass``. + +Following is a reference that shows ``do_split_packages`` mandatory and +optional arguments: +:: + + Mandatory arguments + + root + The path in which to search + file_regex + Regular expression to match searched files. + Use parentheses () to mark the part of this + expression that should be used to derive the + module name (to be substituted where %s is + used in other function arguments as noted below) + output_pattern + Pattern to use for the package names. Must + include %s. + description + Description to set for each package. Must + include %s. + + Optional arguments + + postinst + Postinstall script to use for all packages + (as a string) + recursive + True to perform a recursive search - default + False + hook + A hook function to be called for every match. + The function will be called with the following + arguments (in the order listed): + + f + Full path to the file/directory match + pkg + The package name + file_regex + As above + output_pattern + As above + modulename + The module name derived using file_regex + extra_depends + Extra runtime dependencies (RDEPENDS) to be + set for all packages. The default value of None + causes a dependency on the main package + (${PN}) - if you do not want this, pass empty + string '' for this parameter. + aux_files_pattern + Extra item(s) to be added to FILES for each + package. Can be a single string item or a list + of strings for multiple items. Must include %s. + postrm + postrm script to use for all packages (as a + string) + allow_dirs + True to allow directories to be matched - + default False + prepend + If True, prepend created packages to PACKAGES + instead of the default False which appends them + match_path + match file_regex on the whole relative path to + the root rather than just the file name + aux_files_pattern_verbatim + Extra item(s) to be added to FILES for each + package, using the actual derived module name + rather than converting it to something legal + for a package name. Can be a single string item + or a list of strings for multiple items. Must + include %s. + allow_links + True to allow symlinks to be matched - default + False + summary + Summary to set for each package. Must include %s; + defaults to description if not set. + + + +Satisfying Dependencies +~~~~~~~~~~~~~~~~~~~~~~~ + +The second part for handling optional module packaging is to ensure that +any dependencies on optional modules from other recipes are satisfied by +your recipe. You can be sure these dependencies are satisfied by using +the :term:`PACKAGES_DYNAMIC` +variable. Here is an example that continues with the ``lighttpd`` recipe +shown earlier: +:: + + PACKAGES_DYNAMIC = "lighttpd-module-.*" + +The name +specified in the regular expression can of course be anything. In this +example, it is ``lighttpd-module-`` and is specified as the prefix to +ensure that any :term:`RDEPENDS` and +:term:`RRECOMMENDS` on a package +name starting with the prefix are satisfied during build time. If you +are using ``do_split_packages`` as described in the previous section, +the value you put in ``PACKAGES_DYNAMIC`` should correspond to the name +pattern specified in the call to ``do_split_packages``. + +Using Runtime Package Management +-------------------------------- + +During a build, BitBake always transforms a recipe into one or more +packages. For example, BitBake takes the ``bash`` recipe and produces a +number of packages (e.g. ``bash``, ``bash-bashbug``, +``bash-completion``, ``bash-completion-dbg``, ``bash-completion-dev``, +``bash-completion-extra``, ``bash-dbg``, and so forth). Not all +generated packages are included in an image. + +In several situations, you might need to update, add, remove, or query +the packages on a target device at runtime (i.e. without having to +generate a new image). Examples of such situations include: + +- You want to provide in-the-field updates to deployed devices (e.g. + security updates). + +- You want to have a fast turn-around development cycle for one or more + applications that run on your device. + +- You want to temporarily install the "debug" packages of various + applications on your device so that debugging can be greatly improved + by allowing access to symbols and source debugging. + +- You want to deploy a more minimal package selection of your device + but allow in-the-field updates to add a larger selection for + customization. + +In all these situations, you have something similar to a more +traditional Linux distribution in that in-field devices are able to +receive pre-compiled packages from a server for installation or update. +Being able to install these packages on a running, in-field device is +what is termed "runtime package management". + +In order to use runtime package management, you need a host or server +machine that serves up the pre-compiled packages plus the required +metadata. You also need package manipulation tools on the target. The +build machine is a likely candidate to act as the server. However, that +machine does not necessarily have to be the package server. The build +machine could push its artifacts to another machine that acts as the +server (e.g. Internet-facing). In fact, doing so is advantageous for a +production environment as getting the packages away from the development +system's build directory prevents accidental overwrites. + +A simple build that targets just one device produces more than one +package database. In other words, the packages produced by a build are +separated out into a couple of different package groupings based on +criteria such as the target's CPU architecture, the target board, or the +C library used on the target. For example, a build targeting the +``qemux86`` device produces the following three package databases: +``noarch``, ``i586``, and ``qemux86``. If you wanted your ``qemux86`` +device to be aware of all the packages that were available to it, you +would need to point it to each of these databases individually. In a +similar way, a traditional Linux distribution usually is configured to +be aware of a number of software repositories from which it retrieves +packages. + +Using runtime package management is completely optional and not required +for a successful build or deployment in any way. But if you want to make +use of runtime package management, you need to do a couple things above +and beyond the basics. The remainder of this section describes what you +need to do. + +Build Considerations +~~~~~~~~~~~~~~~~~~~~ + +This section describes build considerations of which you need to be +aware in order to provide support for runtime package management. + +When BitBake generates packages, it needs to know what format or formats +to use. In your configuration, you use the +:term:`PACKAGE_CLASSES` +variable to specify the format: + +1. Open the ``local.conf`` file inside your + :term:`Build Directory` (e.g. + ``~/poky/build/conf/local.conf``). + +2. Select the desired package format as follows: + :: + + PACKAGE_CLASSES ?= "package_packageformat" + + where packageformat can be "ipk", "rpm", + "deb", or "tar" which are the supported package formats. + + .. note:: + + Because the Yocto Project supports four different package formats, + you can set the variable with more than one argument. However, the + OpenEmbedded build system only uses the first argument when + creating an image or Software Development Kit (SDK). + +If you would like your image to start off with a basic package database +containing the packages in your current build as well as to have the +relevant tools available on the target for runtime package management, +you can include "package-management" in the +:term:`IMAGE_FEATURES` +variable. Including "package-management" in this configuration variable +ensures that when the image is assembled for your target, the image +includes the currently-known package databases as well as the +target-specific tools required for runtime package management to be +performed on the target. However, this is not strictly necessary. You +could start your image off without any databases but only include the +required on-target package tool(s). As an example, you could include +"opkg" in your +:term:`IMAGE_INSTALL` variable +if you are using the IPK package format. You can then initialize your +target's package database(s) later once your image is up and running. + +Whenever you perform any sort of build step that can potentially +generate a package or modify existing package, it is always a good idea +to re-generate the package index after the build by using the following +command: +:: + + $ bitbake package-index + +It might be tempting to build the +package and the package index at the same time with a command such as +the following: +:: + + $ bitbake some-package package-index + +Do not do this as +BitBake does not schedule the package index for after the completion of +the package you are building. Consequently, you cannot be sure of the +package index including information for the package you just built. +Thus, be sure to run the package update step separately after building +any packages. + +You can use the +:term:`PACKAGE_FEED_ARCHS`, +:term:`PACKAGE_FEED_BASE_PATHS`, +and +:term:`PACKAGE_FEED_URIS` +variables to pre-configure target images to use a package feed. If you +do not define these variables, then manual steps as described in the +subsequent sections are necessary to configure the target. You should +set these variables before building the image in order to produce a +correctly configured image. + +When your build is complete, your packages reside in the +``${TMPDIR}/deploy/packageformat`` directory. For example, if +``${``\ :term:`TMPDIR`\ ``}`` is +``tmp`` and your selected package type is RPM, then your RPM packages +are available in ``tmp/deploy/rpm``. + +Host or Server Machine Setup +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Although other protocols are possible, a server using HTTP typically +serves packages. If you want to use HTTP, then set up and configure a +web server such as Apache 2, lighttpd, or Python web server on the +machine serving the packages. + +To keep things simple, this section describes how to set up a +Python web server to share package feeds from the developer's +machine. Although this server might not be the best for a production +environment, the setup is simple and straight forward. Should you want +to use a different server more suited for production (e.g. Apache 2, +Lighttpd, or Nginx), take the appropriate steps to do so. + +From within the build directory where you have built an image based on +your packaging choice (i.e. the +:term:`PACKAGE_CLASSES` +setting), simply start the server. The following example assumes a build +directory of ``~/poky/build/tmp/deploy/rpm`` and a ``PACKAGE_CLASSES`` +setting of "package_rpm": +:: + + $ cd ~/poky/build/tmp/deploy/rpm + $ python3 -m http.server + +Target Setup +~~~~~~~~~~~~ + +Setting up the target differs depending on the package management +system. This section provides information for RPM, IPK, and DEB. + +Using RPM +^^^^^^^^^ + +The `Dandified Packaging +Tool <https://en.wikipedia.org/wiki/DNF_(software)>`__ (DNF) performs +runtime package management of RPM packages. In order to use DNF for +runtime package management, you must perform an initial setup on the +target machine for cases where the ``PACKAGE_FEED_*`` variables were not +set as part of the image that is running on the target. This means if +you built your image and did not not use these variables as part of the +build and your image is now running on the target, you need to perform +the steps in this section if you want to use runtime package management. + +.. note:: + + For information on the ``PACKAGE_FEED_*`` variables, see + :term:`PACKAGE_FEED_ARCHS`, :term:`PACKAGE_FEED_BASE_PATHS`, and + :term:`PACKAGE_FEED_URIS` in the Yocto Project Reference Manual variables + glossary. + +On the target, you must inform DNF that package databases are available. +You do this by creating a file named +``/etc/yum.repos.d/oe-packages.repo`` and defining the ``oe-packages``. + +As an example, assume the target is able to use the following package +databases: ``all``, ``i586``, and ``qemux86`` from a server named +``my.server``. The specifics for setting up the web server are up to +you. The critical requirement is that the URIs in the target repository +configuration point to the correct remote location for the feeds. + +.. note:: + + For development purposes, you can point the web server to the build + system's ``deploy`` directory. However, for production use, it is better to + copy the package directories to a location outside of the build area and use + that location. Doing so avoids situations where the build system + overwrites or changes the ``deploy`` directory. + +When telling DNF where to look for the package databases, you must +declare individual locations per architecture or a single location used +for all architectures. You cannot do both: + +- *Create an Explicit List of Architectures:* Define individual base + URLs to identify where each package database is located: + + .. code-block:: none + + [oe-packages] + baseurl=http://my.server/rpm/i586 http://my.server/rpm/qemux86 http://my.server/rpm/all + + This example + informs DNF about individual package databases for all three + architectures. + +- *Create a Single (Full) Package Index:* Define a single base URL that + identifies where a full package database is located: + :: + + [oe-packages] + baseurl=http://my.server/rpm + + This example informs DNF about a single + package database that contains all the package index information for + all supported architectures. + +Once you have informed DNF where to find the package databases, you need +to fetch them: + +.. code-block:: none + + # dnf makecache + +DNF is now able to find, install, and +upgrade packages from the specified repository or repositories. + +.. note:: + + See the `DNF documentation <https://dnf.readthedocs.io/en/latest/>`__ for + additional information. + +Using IPK +^^^^^^^^^ + +The ``opkg`` application performs runtime package management of IPK +packages. You must perform an initial setup for ``opkg`` on the target +machine if the +:term:`PACKAGE_FEED_ARCHS`, +:term:`PACKAGE_FEED_BASE_PATHS`, +and +:term:`PACKAGE_FEED_URIS` +variables have not been set or the target image was built before the +variables were set. + +The ``opkg`` application uses configuration files to find available +package databases. Thus, you need to create a configuration file inside +the ``/etc/opkg/`` direction, which informs ``opkg`` of any repository +you want to use. + +As an example, suppose you are serving packages from a ``ipk/`` +directory containing the ``i586``, ``all``, and ``qemux86`` databases +through an HTTP server named ``my.server``. On the target, create a +configuration file (e.g. ``my_repo.conf``) inside the ``/etc/opkg/`` +directory containing the following: + +.. code-block:: none + + src/gz all http://my.server/ipk/all + src/gz i586 http://my.server/ipk/i586 + src/gz qemux86 http://my.server/ipk/qemux86 + +Next, instruct ``opkg`` to fetch the +repository information: + +.. code-block:: none + + # opkg update + +The ``opkg`` application is now able to find, install, and upgrade packages +from the specified repository. + +Using DEB +^^^^^^^^^ + +The ``apt`` application performs runtime package management of DEB +packages. This application uses a source list file to find available +package databases. You must perform an initial setup for ``apt`` on the +target machine if the +:term:`PACKAGE_FEED_ARCHS`, +:term:`PACKAGE_FEED_BASE_PATHS`, +and +:term:`PACKAGE_FEED_URIS` +variables have not been set or the target image was built before the +variables were set. + +To inform ``apt`` of the repository you want to use, you might create a +list file (e.g. ``my_repo.list``) inside the +``/etc/apt/sources.list.d/`` directory. As an example, suppose you are +serving packages from a ``deb/`` directory containing the ``i586``, +``all``, and ``qemux86`` databases through an HTTP server named +``my.server``. The list file should contain: + +.. code-block:: none + + deb http://my.server/deb/all ./ + deb http://my.server/deb/i586 ./ + deb http://my.server/deb/qemux86 ./ + +Next, instruct the ``apt`` application +to fetch the repository information: + +.. code-block:: none + + # apt-get update + +After this step, +``apt`` is able to find, install, and upgrade packages from the +specified repository. + +Generating and Using Signed Packages +------------------------------------ + +In order to add security to RPM packages used during a build, you can +take steps to securely sign them. Once a signature is verified, the +OpenEmbedded build system can use the package in the build. If security +fails for a signed package, the build system aborts the build. + +This section describes how to sign RPM packages during a build and how +to use signed package feeds (repositories) when doing a build. + +Signing RPM Packages +~~~~~~~~~~~~~~~~~~~~ + +To enable signing RPM packages, you must set up the following +configurations in either your ``local.config`` or ``distro.config`` +file: +:: + + # Inherit sign_rpm.bbclass to enable signing functionality + INHERIT += " sign_rpm" + # Define the GPG key that will be used for signing. + RPM_GPG_NAME = "key_name" + # Provide passphrase for the key + RPM_GPG_PASSPHRASE = "passphrase" + +.. note:: + + Be sure to supply appropriate values for both `key_name` and + `passphrase`. + +Aside from the ``RPM_GPG_NAME`` and ``RPM_GPG_PASSPHRASE`` variables in +the previous example, two optional variables related to signing exist: + +- *GPG_BIN:* Specifies a ``gpg`` binary/wrapper that is executed + when the package is signed. + +- *GPG_PATH:* Specifies the ``gpg`` home directory used when the + package is signed. + +Processing Package Feeds +~~~~~~~~~~~~~~~~~~~~~~~~ + +In addition to being able to sign RPM packages, you can also enable +signed package feeds for IPK and RPM packages. + +The steps you need to take to enable signed package feed use are similar +to the steps used to sign RPM packages. You must define the following in +your ``local.config`` or ``distro.config`` file: +:: + + INHERIT += "sign_package_feed" + PACKAGE_FEED_GPG_NAME = "key_name" + PACKAGE_FEED_GPG_PASSPHRASE_FILE = "path_to_file_containing_passphrase" + +For signed package feeds, the passphrase must exist in a separate file, +which is pointed to by the ``PACKAGE_FEED_GPG_PASSPHRASE_FILE`` +variable. Regarding security, keeping a plain text passphrase out of the +configuration is more secure. + +Aside from the ``PACKAGE_FEED_GPG_NAME`` and +``PACKAGE_FEED_GPG_PASSPHRASE_FILE`` variables, three optional variables +related to signed package feeds exist: + +- *GPG_BIN* Specifies a ``gpg`` binary/wrapper that is executed + when the package is signed. + +- *GPG_PATH:* Specifies the ``gpg`` home directory used when the + package is signed. + +- *PACKAGE_FEED_GPG_SIGNATURE_TYPE:* Specifies the type of ``gpg`` + signature. This variable applies only to RPM and IPK package feeds. + Allowable values for the ``PACKAGE_FEED_GPG_SIGNATURE_TYPE`` are + "ASC", which is the default and specifies ascii armored, and "BIN", + which specifies binary. + +Testing Packages With ptest +--------------------------- + +A Package Test (ptest) runs tests against packages built by the +OpenEmbedded build system on the target machine. A ptest contains at +least two items: the actual test, and a shell script (``run-ptest``) +that starts the test. The shell script that starts the test must not +contain the actual test - the script only starts the test. On the other +hand, the test can be anything from a simple shell script that runs a +binary and checks the output to an elaborate system of test binaries and +data files. + +The test generates output in the format used by Automake: +:: + + result: testname + +where the result can be ``PASS``, ``FAIL``, or ``SKIP``, and +the testname can be any identifying string. + +For a list of Yocto Project recipes that are already enabled with ptest, +see the :yocto_wiki:`Ptest </Ptest>` wiki page. + +.. note:: + + A recipe is "ptest-enabled" if it inherits the + :ref:`ptest <ref-classes-ptest>` class. + +Adding ptest to Your Build +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To add package testing to your build, add the +:term:`DISTRO_FEATURES` and +:term:`EXTRA_IMAGE_FEATURES` +variables to your ``local.conf`` file, which is found in the +:term:`Build Directory`: +:: + + DISTRO_FEATURES_append = " ptest" + EXTRA_IMAGE_FEATURES += "ptest-pkgs" + +Once your build is complete, the ptest files are installed into the +``/usr/lib/package/ptest`` directory within the image, where ``package`` +is the name of the package. + +Running ptest +~~~~~~~~~~~~~ + +The ``ptest-runner`` package installs a shell script that loops through +all installed ptest test suites and runs them in sequence. Consequently, +you might want to add this package to your image. + +Getting Your Package Ready +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In order to enable a recipe to run installed ptests on target hardware, +you need to prepare the recipes that build the packages you want to +test. Here is what you have to do for each recipe: + +- *Be sure the recipe inherits + the* :ref:`ptest <ref-classes-ptest>` *class:* + Include the following line in each recipe: + :: + + inherit ptest + +- *Create run-ptest:* This script starts your test. Locate the + script where you will refer to it using + :term:`SRC_URI`. Here is an + example that starts a test for ``dbus``: + :: + + #!/bin/sh + cd test + make -k runtest-TESTS + +- *Ensure dependencies are met:* If the test adds build or runtime + dependencies that normally do not exist for the package (such as + requiring "make" to run the test suite), use the + :term:`DEPENDS` and + :term:`RDEPENDS` variables in + your recipe in order for the package to meet the dependencies. Here + is an example where the package has a runtime dependency on "make": + :: + + RDEPENDS_${PN}-ptest += "make" + +- *Add a function to build the test suite:* Not many packages support + cross-compilation of their test suites. Consequently, you usually + need to add a cross-compilation function to the package. + + Many packages based on Automake compile and run the test suite by + using a single command such as ``make check``. However, the host + ``make check`` builds and runs on the same computer, while + cross-compiling requires that the package is built on the host but + executed for the target architecture (though often, as in the case + for ptest, the execution occurs on the host). The built version of + Automake that ships with the Yocto Project includes a patch that + separates building and execution. Consequently, packages that use the + unaltered, patched version of ``make check`` automatically + cross-compiles. + + Regardless, you still must add a ``do_compile_ptest`` function to + build the test suite. Add a function similar to the following to your + recipe: + :: + + do_compile_ptest() { + oe_runmake buildtest-TESTS + } + +- *Ensure special configurations are set:* If the package requires + special configurations prior to compiling the test code, you must + insert a ``do_configure_ptest`` function into the recipe. + +- *Install the test suite:* The ``ptest`` class automatically copies + the file ``run-ptest`` to the target and then runs make + ``install-ptest`` to run the tests. If this is not enough, you need + to create a ``do_install_ptest`` function and make sure it gets + called after the "make install-ptest" completes. + +Creating Node Package Manager (NPM) Packages +-------------------------------------------- + +`NPM <https://en.wikipedia.org/wiki/Npm_(software)>`__ is a package +manager for the JavaScript programming language. The Yocto Project +supports the NPM :ref:`fetcher <bitbake:bitbake-user-manual/bitbake-user-manual-fetching:fetchers>`. You can +use this fetcher in combination with +:doc:`devtool </ref-manual/ref-devtool-reference>` to create +recipes that produce NPM packages. + +Two workflows exist that allow you to create NPM packages using +``devtool``: the NPM registry modules method and the NPM project code +method. + +.. note:: + + While it is possible to create NPM recipes manually, using + ``devtool`` is far simpler. + +Additionally, some requirements and caveats exist. + +Requirements and Caveats +~~~~~~~~~~~~~~~~~~~~~~~~ + +You need to be aware of the following before using ``devtool`` to create +NPM packages: + +- Of the two methods that you can use ``devtool`` to create NPM + packages, the registry approach is slightly simpler. However, you + might consider the project approach because you do not have to + publish your module in the NPM registry + (`npm-registry <https://docs.npmjs.com/misc/registry>`_), which + is NPM's public registry. + +- Be familiar with + :doc:`devtool </ref-manual/ref-devtool-reference>`. + +- The NPM host tools need the native ``nodejs-npm`` package, which is + part of the OpenEmbedded environment. You need to get the package by + cloning the https://github.com/openembedded/meta-openembedded + repository out of GitHub. Be sure to add the path to your local copy + to your ``bblayers.conf`` file. + +- ``devtool`` cannot detect native libraries in module dependencies. + Consequently, you must manually add packages to your recipe. + +- While deploying NPM packages, ``devtool`` cannot determine which + dependent packages are missing on the target (e.g. the node runtime + ``nodejs``). Consequently, you need to find out what files are + missing and be sure they are on the target. + +- Although you might not need NPM to run your node package, it is + useful to have NPM on your target. The NPM package name is + ``nodejs-npm``. + +Using the Registry Modules Method +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This section presents an example that uses the ``cute-files`` module, +which is a file browser web application. + +.. note:: + + You must know the ``cute-files`` module version. + +The first thing you need to do is use ``devtool`` and the NPM fetcher to +create the recipe: +:: + + $ devtool add "npm://registry.npmjs.org;package=cute-files;version=1.0.2" + +The +``devtool add`` command runs ``recipetool create`` and uses the same +fetch URI to download each dependency and capture license details where +possible. The result is a generated recipe. + +The recipe file is fairly simple and contains every license that +``recipetool`` finds and includes the licenses in the recipe's +:term:`LIC_FILES_CHKSUM` +variables. You need to examine the variables and look for those with +"unknown" in the :term:`LICENSE` +field. You need to track down the license information for "unknown" +modules and manually add the information to the recipe. + +``recipetool`` creates a "shrinkwrap" file for your recipe. Shrinkwrap +files capture the version of all dependent modules. Many packages do not +provide shrinkwrap files. ``recipetool`` create a shrinkwrap file as it +runs. + +.. note:: + + A package is created for each sub-module. This policy is the only + practical way to have the licenses for all of the dependencies + represented in the license manifest of the image. + +The ``devtool edit-recipe`` command lets you take a look at the recipe: +:: + + $ devtool edit-recipe cute-files + SUMMARY = "Turn any folder on your computer into a cute file browser, available on the local network." + LICENSE = "MIT & ISC & Unknown" + LIC_FILES_CHKSUM = "file://LICENSE;md5=71d98c0a1db42956787b1909c74a86ca \ + file://node_modules/toidentifier/LICENSE;md5=1a261071a044d02eb6f2bb47f51a3502 \ + file://node_modules/debug/LICENSE;md5=ddd815a475e7338b0be7a14d8ee35a99 \ + ... + SRC_URI = " \ + npm://registry.npmjs.org/;package=cute-files;version=${PV} \ + npmsw://${THISDIR}/${BPN}/npm-shrinkwrap.json \ + " + S = "${WORKDIR}/npm" + inherit npm LICENSE_${PN} = "MIT" + LICENSE_${PN}-accepts = "MIT" + LICENSE_${PN}-array-flatten = "MIT" + ... + LICENSE_${PN}-vary = "MIT" + +Three key points exist in the previous example: + +- :term:`SRC_URI` uses the NPM + scheme so that the NPM fetcher is used. + +- ``recipetool`` collects all the license information. If a + sub-module's license is unavailable, the sub-module's name appears in + the comments. + +- The ``inherit npm`` statement causes the + :ref:`npm <ref-classes-npm>` class to package + up all the modules. + +You can run the following command to build the ``cute-files`` package: +:: + + $ devtool build cute-files + +Remember that ``nodejs`` must be installed on +the target before your package. + +Assuming 192.168.7.2 for the target's IP address, use the following +command to deploy your package: +:: + + $ devtool deploy-target -s cute-files root@192.168.7.2 + +Once the package is installed on the target, you can +test the application: + +.. note:: + + Because of a known issue, you cannot simply run ``cute-files`` as you would + if you had run ``npm install``. + +:: + + $ cd /usr/lib/node_modules/cute-files + $ node cute-files.js + +On a browser, +go to ``http://192.168.7.2:3000`` and you see the following: + +.. image:: figures/cute-files-npm-example.png + :align: center + +You can find the recipe in ``workspace/recipes/cute-files``. You can use +the recipe in any layer you choose. + +Using the NPM Projects Code Method +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Although it is useful to package modules already in the NPM registry, +adding ``node.js`` projects under development is a more common developer +use case. + +This section covers the NPM projects code method, which is very similar +to the "registry" approach described in the previous section. In the NPM +projects method, you provide ``devtool`` with an URL that points to the +source files. + +Replicating the same example, (i.e. ``cute-files``) use the following +command: +:: + + $ devtool add https://github.com/martinaglv/cute-files.git + +The +recipe this command generates is very similar to the recipe created in +the previous section. However, the ``SRC_URI`` looks like the following: +:: + + SRC_URI = " \ + git://github.com/martinaglv/cute-files.git;protocol=https \ + npmsw://${THISDIR}/${BPN}/npm-shrinkwrap.json \ + " + +In this example, +the main module is taken from the Git repository and dependencies are +taken from the NPM registry. Other than those differences, the recipe is +basically the same between the two methods. You can build and deploy the +package exactly as described in the previous section that uses the +registry modules method. + +Adding custom metadata to packages +---------------------------------- + +The variable +:term:`PACKAGE_ADD_METADATA` +can be used to add additional metadata to packages. This is reflected in +the package control/spec file. To take the ipk format for example, the +CONTROL file stored inside would contain the additional metadata as +additional lines. + +The variable can be used in multiple ways, including using suffixes to +set it for a specific package type and/or package. Note that the order +of precedence is the same as this list: + +- ``PACKAGE_ADD_METADATA_<PKGTYPE>_<PN>`` + +- ``PACKAGE_ADD_METADATA_<PKGTYPE>`` + +- ``PACKAGE_ADD_METADATA_<PN>`` + +- ``PACKAGE_ADD_METADATA`` + +`<PKGTYPE>` is a parameter and expected to be a distinct name of specific +package type: + +- IPK for .ipk packages + +- DEB for .deb packages + +- RPM for .rpm packages + +`<PN>` is a parameter and expected to be a package name. + +The variable can contain multiple [one-line] metadata fields separated +by the literal sequence '\\n'. The separator can be redefined using the +variable flag ``separator``. + +The following is an example that adds two custom fields for ipk +packages: +:: + + PACKAGE_ADD_METADATA_IPK = "Vendor: CustomIpk\nGroup:Applications/Spreadsheets" + +Efficiently Fetching Source Files During a Build +================================================ + +The OpenEmbedded build system works with source files located through +the :term:`SRC_URI` variable. When +you build something using BitBake, a big part of the operation is +locating and downloading all the source tarballs. For images, +downloading all the source for various packages can take a significant +amount of time. + +This section shows you how you can use mirrors to speed up fetching +source files and how you can pre-fetch files all of which leads to more +efficient use of resources and time. + +Setting up Effective Mirrors +---------------------------- + +A good deal that goes into a Yocto Project build is simply downloading +all of the source tarballs. Maybe you have been working with another +build system (OpenEmbedded or Angstrom) for which you have built up a +sizable directory of source tarballs. Or, perhaps someone else has such +a directory for which you have read access. If so, you can save time by +adding statements to your configuration file so that the build process +checks local directories first for existing tarballs before checking the +Internet. + +Here is an efficient way to set it up in your ``local.conf`` file: +:: + + SOURCE_MIRROR_URL ?= "file:///home/you/your-download-dir/" + INHERIT += "own-mirrors" + BB_GENERATE_MIRROR_TARBALLS = "1" + # BB_NO_NETWORK = "1" + +In the previous example, the +:term:`BB_GENERATE_MIRROR_TARBALLS` +variable causes the OpenEmbedded build system to generate tarballs of +the Git repositories and store them in the +:term:`DL_DIR` directory. Due to +performance reasons, generating and storing these tarballs is not the +build system's default behavior. + +You can also use the +:term:`PREMIRRORS` variable. For +an example, see the variable's glossary entry in the Yocto Project +Reference Manual. + +Getting Source Files and Suppressing the Build +---------------------------------------------- + +Another technique you can use to ready yourself for a successive string +of build operations, is to pre-fetch all the source files without +actually starting a build. This technique lets you work through any +download issues and ultimately gathers all the source files into your +download directory :ref:`structure-build-downloads`, +which is located with :term:`DL_DIR`. + +Use the following BitBake command form to fetch all the necessary +sources without starting the build: +:: + + $ bitbake target --runall=fetch + +This +variation of the BitBake command guarantees that you have all the +sources for that BitBake target should you disconnect from the Internet +and want to do the build later offline. + +Selecting an Initialization Manager +=================================== + +By default, the Yocto Project uses SysVinit as the initialization +manager. However, support also exists for systemd, which is a full +replacement for init with parallel starting of services, reduced shell +overhead and other features that are used by many distributions. + +Within the system, SysVinit treats system components as services. These +services are maintained as shell scripts stored in the ``/etc/init.d/`` +directory. Services organize into different run levels. This +organization is maintained by putting links to the services in the +``/etc/rcN.d/`` directories, where `N/` is one of the following options: +"S", "0", "1", "2", "3", "4", "5", or "6". + +.. note:: + + Each runlevel has a dependency on the previous runlevel. This + dependency allows the services to work properly. + +In comparison, systemd treats components as units. Using units is a +broader concept as compared to using a service. A unit includes several +different types of entities. Service is one of the types of entities. +The runlevel concept in SysVinit corresponds to the concept of a target +in systemd, where target is also a type of supported unit. + +In a SysVinit-based system, services load sequentially (i.e. one by one) +during init and parallelization is not supported. With systemd, services +start in parallel. Needless to say, the method can have an impact on +system startup performance. + +If you want to use SysVinit, you do not have to do anything. But, if you +want to use systemd, you must take some steps as described in the +following sections. + +Using systemd Exclusively +------------------------- + +Set these variables in your distribution configuration file as follows: +:: + + DISTRO_FEATURES_append = " systemd" + VIRTUAL-RUNTIME_init_manager = "systemd" + +You can also prevent the SysVinit distribution feature from +being automatically enabled as follows: +:: + + DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit" + +Doing so removes any +redundant SysVinit scripts. + +To remove initscripts from your image altogether, set this variable +also: +:: + + VIRTUAL-RUNTIME_initscripts = "" + +For information on the backfill variable, see +:term:`DISTRO_FEATURES_BACKFILL_CONSIDERED`. + +Using systemd for the Main Image and Using SysVinit for the Rescue Image +------------------------------------------------------------------------ + +Set these variables in your distribution configuration file as follows: +:: + + DISTRO_FEATURES_append = " systemd" + VIRTUAL-RUNTIME_init_manager = "systemd" + +Doing so causes your main image to use the +``packagegroup-core-boot.bb`` recipe and systemd. The rescue/minimal +image cannot use this package group. However, it can install SysVinit +and the appropriate packages will have support for both systemd and +SysVinit. + +Selecting a Device Manager +========================== + +The Yocto Project provides multiple ways to manage the device manager +(``/dev``): + +- Persistent and Pre-Populated\ ``/dev``: For this case, the ``/dev`` + directory is persistent and the required device nodes are created + during the build. + +- Use ``devtmpfs`` with a Device Manager: For this case, the ``/dev`` + directory is provided by the kernel as an in-memory file system and + is automatically populated by the kernel at runtime. Additional + configuration of device nodes is done in user space by a device + manager like ``udev`` or ``busybox-mdev``. + +Using Persistent and Pre-Populated\ ``/dev`` +-------------------------------------------- + +To use the static method for device population, you need to set the +:term:`USE_DEVFS` variable to "0" +as follows: +:: + + USE_DEVFS = "0" + +The content of the resulting ``/dev`` directory is defined in a Device +Table file. The +:term:`IMAGE_DEVICE_TABLES` +variable defines the Device Table to use and should be set in the +machine or distro configuration file. Alternatively, you can set this +variable in your ``local.conf`` configuration file. + +If you do not define the ``IMAGE_DEVICE_TABLES`` variable, the default +``device_table-minimal.txt`` is used: +:: + + IMAGE_DEVICE_TABLES = "device_table-mymachine.txt" + +The population is handled by the ``makedevs`` utility during image +creation: + +Using ``devtmpfs`` and a Device Manager +--------------------------------------- + +To use the dynamic method for device population, you need to use (or be +sure to set) the :term:`USE_DEVFS` +variable to "1", which is the default: +:: + + USE_DEVFS = "1" + +With this +setting, the resulting ``/dev`` directory is populated by the kernel +using ``devtmpfs``. Make sure the corresponding kernel configuration +variable ``CONFIG_DEVTMPFS`` is set when building you build a Linux +kernel. + +All devices created by ``devtmpfs`` will be owned by ``root`` and have +permissions ``0600``. + +To have more control over the device nodes, you can use a device manager +like ``udev`` or ``busybox-mdev``. You choose the device manager by +defining the ``VIRTUAL-RUNTIME_dev_manager`` variable in your machine or +distro configuration file. Alternatively, you can set this variable in +your ``local.conf`` configuration file: +:: + + VIRTUAL-RUNTIME_dev_manager = "udev" + + # Some alternative values + # VIRTUAL-RUNTIME_dev_manager = "busybox-mdev" + # VIRTUAL-RUNTIME_dev_manager = "systemd" + +Using an External SCM +===================== + +If you're working on a recipe that pulls from an external Source Code +Manager (SCM), it is possible to have the OpenEmbedded build system +notice new recipe changes added to the SCM and then build the resulting +packages that depend on the new recipes by using the latest versions. +This only works for SCMs from which it is possible to get a sensible +revision number for changes. Currently, you can do this with Apache +Subversion (SVN), Git, and Bazaar (BZR) repositories. + +To enable this behavior, the :term:`PV` of +the recipe needs to reference +:term:`SRCPV`. Here is an example: +:: + + PV = "1.2.3+git${SRCPV}" + +Then, you can add the following to your +``local.conf``: +:: + + SRCREV_pn-PN = "${AUTOREV}" + +:term:`PN` is the name of the recipe for +which you want to enable automatic source revision updating. + +If you do not want to update your local configuration file, you can add +the following directly to the recipe to finish enabling the feature: +:: + + SRCREV = "${AUTOREV}" + +The Yocto Project provides a distribution named ``poky-bleeding``, whose +configuration file contains the line: +:: + + require conf/distro/include/poky-floating-revisions.inc + +This line pulls in the +listed include file that contains numerous lines of exactly that form: +:: + + #SRCREV_pn-opkg-native ?= "${AUTOREV}" + #SRCREV_pn-opkg-sdk ?= "${AUTOREV}" + #SRCREV_pn-opkg ?= "${AUTOREV}" + #SRCREV_pn-opkg-utils-native ?= "${AUTOREV}" + #SRCREV_pn-opkg-utils ?= "${AUTOREV}" + SRCREV_pn-gconf-dbus ?= "${AUTOREV}" + SRCREV_pn-matchbox-common ?= "${AUTOREV}" + SRCREV_pn-matchbox-config-gtk ?= "${AUTOREV}" + SRCREV_pn-matchbox-desktop ?= "${AUTOREV}" + SRCREV_pn-matchbox-keyboard ?= "${AUTOREV}" + SRCREV_pn-matchbox-panel-2 ?= "${AUTOREV}" + SRCREV_pn-matchbox-themes-extra ?= "${AUTOREV}" + SRCREV_pn-matchbox-terminal ?= "${AUTOREV}" + SRCREV_pn-matchbox-wm ?= "${AUTOREV}" + SRCREV_pn-settings-daemon ?= "${AUTOREV}" + SRCREV_pn-screenshot ?= "${AUTOREV}" + . . . + +These lines allow you to +experiment with building a distribution that tracks the latest +development source for numerous packages. + +.. note:: + + The ``poky-bleeding`` distribution is not tested on a regular basis. Keep + this in mind if you use it. + +Creating a Read-Only Root Filesystem +==================================== + +Suppose, for security reasons, you need to disable your target device's +root filesystem's write permissions (i.e. you need a read-only root +filesystem). Or, perhaps you are running the device's operating system +from a read-only storage device. For either case, you can customize your +image for that behavior. + +.. note:: + + Supporting a read-only root filesystem requires that the system and + applications do not try to write to the root filesystem. You must + configure all parts of the target system to write elsewhere, or to + gracefully fail in the event of attempting to write to the root + filesystem. + +Creating the Root Filesystem +---------------------------- + +To create the read-only root filesystem, simply add the +"read-only-rootfs" feature to your image, normally in one of two ways. +The first way is to add the "read-only-rootfs" image feature in the +image's recipe file via the ``IMAGE_FEATURES`` variable: +:: + + IMAGE_FEATURES += "read-only-rootfs" + +As an alternative, you can add the same feature +from within your build directory's ``local.conf`` file with the +associated ``EXTRA_IMAGE_FEATURES`` variable, as in: +:: + + EXTRA_IMAGE_FEATURES = "read-only-rootfs" + +For more information on how to use these variables, see the +":ref:`dev-manual/common-tasks:Customizing Images Using Custom \`\`IMAGE_FEATURES\`\` and \`\`EXTRA_IMAGE_FEATURES\`\``" +section. For information on the variables, see +:term:`IMAGE_FEATURES` and +:term:`EXTRA_IMAGE_FEATURES`. + +Post-Installation Scripts and Read-Only Root Filesystem +------------------------------------------------------- + +It is very important that you make sure all post-Installation +(``pkg_postinst``) scripts for packages that are installed into the +image can be run at the time when the root filesystem is created during +the build on the host system. These scripts cannot attempt to run during +first-boot on the target device. With the "read-only-rootfs" feature +enabled, the build system checks during root filesystem creation to make +sure all post-installation scripts succeed. If any of these scripts +still need to be run after the root filesystem is created, the build +immediately fails. These build-time checks ensure that the build fails +rather than the target device fails later during its initial boot +operation. + +Most of the common post-installation scripts generated by the build +system for the out-of-the-box Yocto Project are engineered so that they +can run during root filesystem creation (e.g. post-installation scripts +for caching fonts). However, if you create and add custom scripts, you +need to be sure they can be run during this file system creation. + +Here are some common problems that prevent post-installation scripts +from running during root filesystem creation: + +- *Not using $D in front of absolute paths:* The build system defines + ``$``\ :term:`D` when the root + filesystem is created. Furthermore, ``$D`` is blank when the script + is run on the target device. This implies two purposes for ``$D``: + ensuring paths are valid in both the host and target environments, + and checking to determine which environment is being used as a method + for taking appropriate actions. + +- *Attempting to run processes that are specific to or dependent on the + target architecture:* You can work around these attempts by using + native tools, which run on the host system, to accomplish the same + tasks, or by alternatively running the processes under QEMU, which + has the ``qemu_run_binary`` function. For more information, see the + :ref:`qemu <ref-classes-qemu>` class. + +Areas With Write Access +----------------------- + +With the "read-only-rootfs" feature enabled, any attempt by the target +to write to the root filesystem at runtime fails. Consequently, you must +make sure that you configure processes and applications that attempt +these types of writes do so to directories with write access (e.g. +``/tmp`` or ``/var/run``). + +Maintaining Build Output Quality +================================ + +Many factors can influence the quality of a build. For example, if you +upgrade a recipe to use a new version of an upstream software package or +you experiment with some new configuration options, subtle changes can +occur that you might not detect until later. Consider the case where +your recipe is using a newer version of an upstream package. In this +case, a new version of a piece of software might introduce an optional +dependency on another library, which is auto-detected. If that library +has already been built when the software is building, the software will +link to the built library and that library will be pulled into your +image along with the new software even if you did not want the library. + +The :ref:`buildhistory <ref-classes-buildhistory>` +class exists to help you maintain the quality of your build output. You +can use the class to highlight unexpected and possibly unwanted changes +in the build output. When you enable build history, it records +information about the contents of each package and image and then +commits that information to a local Git repository where you can examine +the information. + +The remainder of this section describes the following: + +- :ref:`How you can enable and disable build history <dev-manual/common-tasks:enabling and disabling build history>` + +- :ref:`How to understand what the build history contains <dev-manual/common-tasks:understanding what the build history contains>` + +- :ref:`How to limit the information used for build history <dev-manual/common-tasks:using build history to gather image information only>` + +- :ref:`How to examine the build history from both a command-line and web interface <dev-manual/common-tasks:examining build history information>` + +Enabling and Disabling Build History +------------------------------------ + +Build history is disabled by default. To enable it, add the following +``INHERIT`` statement and set the +:term:`BUILDHISTORY_COMMIT` +variable to "1" at the end of your ``conf/local.conf`` file found in the +:term:`Build Directory`: +:: + + INHERIT += "buildhistory" + BUILDHISTORY_COMMIT = "1" + +Enabling build history as +previously described causes the OpenEmbedded build system to collect +build output information and commit it as a single commit to a local +:ref:`overview-manual/overview-manual-development-environment:git` repository. + +.. note:: + + Enabling build history increases your build times slightly, + particularly for images, and increases the amount of disk space used + during the build. + +You can disable build history by removing the previous statements from +your ``conf/local.conf`` file. + +Understanding What the Build History Contains +--------------------------------------------- + +Build history information is kept in +``${``\ :term:`TOPDIR`\ ``}/buildhistory`` +in the Build Directory as defined by the +:term:`BUILDHISTORY_DIR` +variable. The following is an example abbreviated listing: + +.. image:: figures/buildhistory.png + :align: center + +At the top level, a ``metadata-revs`` file exists that lists the +revisions of the repositories for the enabled layers when the build was +produced. The rest of the data splits into separate ``packages``, +``images`` and ``sdk`` directories, the contents of which are described +as follows. + +Build History Package Information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The history for each package contains a text file that has name-value +pairs with information about the package. For example, +``buildhistory/packages/i586-poky-linux/busybox/busybox/latest`` +contains the following: + +.. code-block:: none + + PV = 1.22.1 + PR = r32 + RPROVIDES = + RDEPENDS = glibc (>= 2.20) update-alternatives-opkg + RRECOMMENDS = busybox-syslog busybox-udhcpc update-rc.d + PKGSIZE = 540168 + FILES = /usr/bin/* /usr/sbin/* /usr/lib/busybox/* /usr/lib/lib*.so.* \ + /etc /com /var /bin/* /sbin/* /lib/*.so.* /lib/udev/rules.d \ + /usr/lib/udev/rules.d /usr/share/busybox /usr/lib/busybox/* \ + /usr/share/pixmaps /usr/share/applications /usr/share/idl \ + /usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers + FILELIST = /bin/busybox /bin/busybox.nosuid /bin/busybox.suid /bin/sh \ + /etc/busybox.links.nosuid /etc/busybox.links.suid + +Most of these +name-value pairs correspond to variables used to produce the package. +The exceptions are ``FILELIST``, which is the actual list of files in +the package, and ``PKGSIZE``, which is the total size of files in the +package in bytes. + +A file also exists that corresponds to the recipe from which the package +came (e.g. ``buildhistory/packages/i586-poky-linux/busybox/latest``): + +.. code-block:: none + + PV = 1.22.1 + PR = r32 + DEPENDS = initscripts kern-tools-native update-rc.d-native \ + virtual/i586-poky-linux-compilerlibs virtual/i586-poky-linux-gcc \ + virtual/libc virtual/update-alternatives + PACKAGES = busybox-ptest busybox-httpd busybox-udhcpd busybox-udhcpc \ + busybox-syslog busybox-mdev busybox-hwclock busybox-dbg \ + busybox-staticdev busybox-dev busybox-doc busybox-locale busybox + +Finally, for those recipes fetched from a version control system (e.g., +Git), a file exists that lists source revisions that are specified in +the recipe and lists the actual revisions used during the build. Listed +and actual revisions might differ when +:term:`SRCREV` is set to +${:term:`AUTOREV`}. Here is an +example assuming +``buildhistory/packages/qemux86-poky-linux/linux-yocto/latest_srcrev``): +:: + + # SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1" + SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1" + # SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f" + SRCREV_meta ="a227f20eff056e511d504b2e490f3774ab260d6f" + +You can use the +``buildhistory-collect-srcrevs`` command with the ``-a`` option to +collect the stored ``SRCREV`` values from build history and report them +in a format suitable for use in global configuration (e.g., +``local.conf`` or a distro include file) to override floating +``AUTOREV`` values to a fixed set of revisions. Here is some example +output from this command: +:: + + $ buildhistory-collect-srcrevs -a + # i586-poky-linux + SRCREV_pn-glibc = "b8079dd0d360648e4e8de48656c5c38972621072" + SRCREV_pn-glibc-initial = "b8079dd0d360648e4e8de48656c5c38972621072" + SRCREV_pn-opkg-utils = "53274f087565fd45d8452c5367997ba6a682a37a" + SRCREV_pn-kmod = "fd56638aed3fe147015bfa10ed4a5f7491303cb4" + # x86_64-linux + SRCREV_pn-gtk-doc-stub-native = "1dea266593edb766d6d898c79451ef193eb17cfa" + SRCREV_pn-dtc-native = "65cc4d2748a2c2e6f27f1cf39e07a5dbabd80ebf" + SRCREV_pn-update-rc.d-native = "eca680ddf28d024954895f59a241a622dd575c11" + SRCREV_glibc_pn-cross-localedef-native = "b8079dd0d360648e4e8de48656c5c38972621072" + SRCREV_localedef_pn-cross-localedef-native = "c833367348d39dad7ba018990bfdaffaec8e9ed3" + SRCREV_pn-prelink-native = "faa069deec99bf61418d0bab831c83d7c1b797ca" + SRCREV_pn-opkg-utils-native = "53274f087565fd45d8452c5367997ba6a682a37a" + SRCREV_pn-kern-tools-native = "23345b8846fe4bd167efdf1bd8a1224b2ba9a5ff" + SRCREV_pn-kmod-native = "fd56638aed3fe147015bfa10ed4a5f7491303cb4" + # qemux86-poky-linux + SRCREV_machine_pn-linux-yocto = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1" + SRCREV_meta_pn-linux-yocto = "a227f20eff056e511d504b2e490f3774ab260d6f" + # all-poky-linux + SRCREV_pn-update-rc.d = "eca680ddf28d024954895f59a241a622dd575c11" + +.. note:: + + Here are some notes on using the ``buildhistory-collect-srcrevs`` command: + + - By default, only values where the ``SRCREV`` was not hardcoded + (usually when ``AUTOREV`` is used) are reported. Use the ``-a`` + option to see all ``SRCREV`` values. + + - The output statements might not have any effect if overrides are + applied elsewhere in the build system configuration. Use the + ``-f`` option to add the ``forcevariable`` override to each output + line if you need to work around this restriction. + + - The script does apply special handling when building for multiple + machines. However, the script does place a comment before each set + of values that specifies which triplet to which they belong as + previously shown (e.g., ``i586-poky-linux``). + +Build History Image Information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The files produced for each image are as follows: + +- ``image-files:`` A directory containing selected files from the root + filesystem. The files are defined by + :term:`BUILDHISTORY_IMAGE_FILES`. + +- ``build-id.txt:`` Human-readable information about the build + configuration and metadata source revisions. This file contains the + full build header as printed by BitBake. + +- ``*.dot:`` Dependency graphs for the image that are compatible with + ``graphviz``. + +- ``files-in-image.txt:`` A list of files in the image with + permissions, owner, group, size, and symlink information. + +- ``image-info.txt:`` A text file containing name-value pairs with + information about the image. See the following listing example for + more information. + +- ``installed-package-names.txt:`` A list of installed packages by name + only. + +- ``installed-package-sizes.txt:`` A list of installed packages ordered + by size. + +- ``installed-packages.txt:`` A list of installed packages with full + package filenames. + +.. note:: + + Installed package information is able to be gathered and produced + even if package management is disabled for the final image. + +Here is an example of ``image-info.txt``: + +.. code-block:: none + + DISTRO = poky + DISTRO_VERSION = 1.7 + USER_CLASSES = buildstats image-mklibs image-prelink + IMAGE_CLASSES = image_types + IMAGE_FEATURES = debug-tweaks + IMAGE_LINGUAS = + IMAGE_INSTALL = packagegroup-core-boot run-postinsts + BAD_RECOMMENDATIONS = + NO_RECOMMENDATIONS = + PACKAGE_EXCLUDE = + ROOTFS_POSTPROCESS_COMMAND = write_package_manifest; license_create_manifest; \ + write_image_manifest ; buildhistory_list_installed_image ; \ + buildhistory_get_image_installed ; ssh_allow_empty_password; \ + postinst_enable_logging; rootfs_update_timestamp ; ssh_disable_dns_lookup ; + IMAGE_POSTPROCESS_COMMAND = buildhistory_get_imageinfo ; + IMAGESIZE = 6900 + +Other than ``IMAGESIZE``, +which is the total size of the files in the image in Kbytes, the +name-value pairs are variables that may have influenced the content of +the image. This information is often useful when you are trying to +determine why a change in the package or file listings has occurred. + +Using Build History to Gather Image Information Only +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As you can see, build history produces image information, including +dependency graphs, so you can see why something was pulled into the +image. If you are just interested in this information and not interested +in collecting specific package or SDK information, you can enable +writing only image information without any history by adding the +following to your ``conf/local.conf`` file found in the +:term:`Build Directory`: +:: + + INHERIT += "buildhistory" + BUILDHISTORY_COMMIT = "0" + BUILDHISTORY_FEATURES = "image" + +Here, you set the +:term:`BUILDHISTORY_FEATURES` +variable to use the image feature only. + +Build History SDK Information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Build history collects similar information on the contents of SDKs (e.g. +``bitbake -c populate_sdk imagename``) as compared to information it +collects for images. Furthermore, this information differs depending on +whether an extensible or standard SDK is being produced. + +The following list shows the files produced for SDKs: + +- ``files-in-sdk.txt:`` A list of files in the SDK with permissions, + owner, group, size, and symlink information. This list includes both + the host and target parts of the SDK. + +- ``sdk-info.txt:`` A text file containing name-value pairs with + information about the SDK. See the following listing example for more + information. + +- ``sstate-task-sizes.txt:`` A text file containing name-value pairs + with information about task group sizes (e.g. ``do_populate_sysroot`` + tasks have a total size). The ``sstate-task-sizes.txt`` file exists + only when an extensible SDK is created. + +- ``sstate-package-sizes.txt:`` A text file containing name-value pairs + with information for the shared-state packages and sizes in the SDK. + The ``sstate-package-sizes.txt`` file exists only when an extensible + SDK is created. + +- ``sdk-files:`` A folder that contains copies of the files mentioned + in ``BUILDHISTORY_SDK_FILES`` if the files are present in the output. + Additionally, the default value of ``BUILDHISTORY_SDK_FILES`` is + specific to the extensible SDK although you can set it differently if + you would like to pull in specific files from the standard SDK. + + The default files are ``conf/local.conf``, ``conf/bblayers.conf``, + ``conf/auto.conf``, ``conf/locked-sigs.inc``, and + ``conf/devtool.conf``. Thus, for an extensible SDK, these files get + copied into the ``sdk-files`` directory. + +- The following information appears under each of the ``host`` and + ``target`` directories for the portions of the SDK that run on the + host and on the target, respectively: + + .. note:: + + The following files for the most part are empty when producing an + extensible SDK because this type of SDK is not constructed from + packages as is the standard SDK. + + - ``depends.dot:`` Dependency graph for the SDK that is compatible + with ``graphviz``. + + - ``installed-package-names.txt:`` A list of installed packages by + name only. + + - ``installed-package-sizes.txt:`` A list of installed packages + ordered by size. + + - ``installed-packages.txt:`` A list of installed packages with full + package filenames. + +Here is an example of ``sdk-info.txt``: + +.. code-block:: none + + DISTRO = poky + DISTRO_VERSION = 1.3+snapshot-20130327 + SDK_NAME = poky-glibc-i686-arm + SDK_VERSION = 1.3+snapshot + SDKMACHINE = + SDKIMAGE_FEATURES = dev-pkgs dbg-pkgs + BAD_RECOMMENDATIONS = + SDKSIZE = 352712 + +Other than ``SDKSIZE``, which is +the total size of the files in the SDK in Kbytes, the name-value pairs +are variables that might have influenced the content of the SDK. This +information is often useful when you are trying to determine why a +change in the package or file listings has occurred. + +Examining Build History Information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You can examine build history output from the command line or from a web +interface. + +To see any changes that have occurred (assuming you have +:term:`BUILDHISTORY_COMMIT` = "1"), +you can simply use any Git command that allows you to view the history +of a repository. Here is one method: +:: + + $ git log -p + +You need to realize, +however, that this method does show changes that are not significant +(e.g. a package's size changing by a few bytes). + +A command-line tool called ``buildhistory-diff`` does exist, though, +that queries the Git repository and prints just the differences that +might be significant in human-readable form. Here is an example: +:: + + $ ~/poky/poky/scripts/buildhistory-diff . HEAD^ + Changes to images/qemux86_64/glibc/core-image-minimal (files-in-image.txt): + /etc/anotherpkg.conf was added + /sbin/anotherpkg was added + * (installed-package-names.txt): + * anotherpkg was added + Changes to images/qemux86_64/glibc/core-image-minimal (installed-package-names.txt): + anotherpkg was added + packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras" + * PR changed from "r0" to "r1" + * PV changed from "0.1.10" to "0.1.12" + packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%) + * PR changed from "r0" to "r1" + * PV changed from "0.1.10" to "0.1.12" + +.. note:: + + The ``buildhistory-diff`` tool requires the ``GitPython`` + package. Be sure to install it using Pip3 as follows: + :: + + $ pip3 install GitPython --user + + + Alternatively, you can install ``python3-git`` using the appropriate + distribution package manager (e.g. ``apt-get``, ``dnf``, or ``zipper``). + +To see changes to the build history using a web interface, follow the +instruction in the ``README`` file +:yocto_git:`here </buildhistory-web/>`. + +Here is a sample screenshot of the interface: + +.. image:: figures/buildhistory-web.png + :align: center + +Performing Automated Runtime Testing +==================================== + +The OpenEmbedded build system makes available a series of automated +tests for images to verify runtime functionality. You can run these +tests on either QEMU or actual target hardware. Tests are written in +Python making use of the ``unittest`` module, and the majority of them +run commands on the target system over SSH. This section describes how +you set up the environment to use these tests, run available tests, and +write and add your own tests. + +For information on the test and QA infrastructure available within the +Yocto Project, see the ":ref:`ref-manual/ref-release-process:testing and quality assurance`" +section in the Yocto Project Reference Manual. + +Enabling Tests +-------------- + +Depending on whether you are planning to run tests using QEMU or on the +hardware, you have to take different steps to enable the tests. See the +following subsections for information on how to enable both types of +tests. + +Enabling Runtime Tests on QEMU +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In order to run tests, you need to do the following: + +- *Set up to avoid interaction with sudo for networking:* To + accomplish this, you must do one of the following: + + - Add ``NOPASSWD`` for your user in ``/etc/sudoers`` either for all + commands or just for ``runqemu-ifup``. You must provide the full + path as that can change if you are using multiple clones of the + source repository. + + .. note:: + + On some distributions, you also need to comment out "Defaults + requiretty" in ``/etc/sudoers``. + + - Manually configure a tap interface for your system. + + - Run as root the script in ``scripts/runqemu-gen-tapdevs``, which + should generate a list of tap devices. This is the option + typically chosen for Autobuilder-type environments. + + .. note:: + + - Be sure to use an absolute path when calling this script + with sudo. + + - The package recipe ``qemu-helper-native`` is required to run + this script. Build the package using the following command: + :: + + $ bitbake qemu-helper-native + +- *Set the DISPLAY variable:* You need to set this variable so that + you have an X server available (e.g. start ``vncserver`` for a + headless machine). + +- *Be sure your host's firewall accepts incoming connections from + 192.168.7.0/24:* Some of the tests (in particular DNF tests) start an + HTTP server on a random high number port, which is used to serve + files to the target. The DNF module serves + ``${WORKDIR}/oe-rootfs-repo`` so it can run DNF channel commands. + That means your host's firewall must accept incoming connections from + 192.168.7.0/24, which is the default IP range used for tap devices by + ``runqemu``. + +- *Be sure your host has the correct packages installed:* Depending + your host's distribution, you need to have the following packages + installed: + + - Ubuntu and Debian: ``sysstat`` and ``iproute2`` + + - OpenSUSE: ``sysstat`` and ``iproute2`` + + - Fedora: ``sysstat`` and ``iproute`` + + - CentOS: ``sysstat`` and ``iproute`` + +Once you start running the tests, the following happens: + +1. A copy of the root filesystem is written to ``${WORKDIR}/testimage``. + +2. The image is booted under QEMU using the standard ``runqemu`` script. + +3. A default timeout of 500 seconds occurs to allow for the boot process + to reach the login prompt. You can change the timeout period by + setting + :term:`TEST_QEMUBOOT_TIMEOUT` + in the ``local.conf`` file. + +4. Once the boot process is reached and the login prompt appears, the + tests run. The full boot log is written to + ``${WORKDIR}/testimage/qemu_boot_log``. + +5. Each test module loads in the order found in ``TEST_SUITES``. You can + find the full output of the commands run over SSH in + ``${WORKDIR}/testimgage/ssh_target_log``. + +6. If no failures occur, the task running the tests ends successfully. + You can find the output from the ``unittest`` in the task log at + ``${WORKDIR}/temp/log.do_testimage``. + +Enabling Runtime Tests on Hardware +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The OpenEmbedded build system can run tests on real hardware, and for +certain devices it can also deploy the image to be tested onto the +device beforehand. + +For automated deployment, a "master image" is installed onto the +hardware once as part of setup. Then, each time tests are to be run, the +following occurs: + +1. The master image is booted into and used to write the image to be + tested to a second partition. + +2. The device is then rebooted using an external script that you need to + provide. + +3. The device boots into the image to be tested. + +When running tests (independent of whether the image has been deployed +automatically or not), the device is expected to be connected to a +network on a pre-determined IP address. You can either use static IP +addresses written into the image, or set the image to use DHCP and have +your DHCP server on the test network assign a known IP address based on +the MAC address of the device. + +In order to run tests on hardware, you need to set ``TEST_TARGET`` to an +appropriate value. For QEMU, you do not have to change anything, the +default value is "qemu". For running tests on hardware, the following +options exist: + +- *"simpleremote":* Choose "simpleremote" if you are going to run tests + on a target system that is already running the image to be tested and + is available on the network. You can use "simpleremote" in + conjunction with either real hardware or an image running within a + separately started QEMU or any other virtual machine manager. + +- *"SystemdbootTarget":* Choose "SystemdbootTarget" if your hardware is + an EFI-based machine with ``systemd-boot`` as bootloader and + ``core-image-testmaster`` (or something similar) is installed. Also, + your hardware under test must be in a DHCP-enabled network that gives + it the same IP address for each reboot. + + If you choose "SystemdbootTarget", there are additional requirements + and considerations. See the "`Selecting + SystemdbootTarget <#selecting-systemdboottarget>`__" section, which + follows, for more information. + +- *"BeagleBoneTarget":* Choose "BeagleBoneTarget" if you are deploying + images and running tests on the BeagleBone "Black" or original + "White" hardware. For information on how to use these tests, see the + comments at the top of the BeagleBoneTarget + ``meta-yocto-bsp/lib/oeqa/controllers/beaglebonetarget.py`` file. + +- *"EdgeRouterTarget":* Choose "EdgeRouterTarget" if you are deploying + images and running tests on the Ubiquiti Networks EdgeRouter Lite. + For information on how to use these tests, see the comments at the + top of the EdgeRouterTarget + ``meta-yocto-bsp/lib/oeqa/controllers/edgeroutertarget.py`` file. + +- *"GrubTarget":* Choose "GrubTarget" if you are deploying images and running + tests on any generic PC that boots using GRUB. For information on how + to use these tests, see the comments at the top of the GrubTarget + ``meta-yocto-bsp/lib/oeqa/controllers/grubtarget.py`` file. + +- *"your-target":* Create your own custom target if you want to run + tests when you are deploying images and running tests on a custom + machine within your BSP layer. To do this, you need to add a Python + unit that defines the target class under ``lib/oeqa/controllers/`` + within your layer. You must also provide an empty ``__init__.py``. + For examples, see files in ``meta-yocto-bsp/lib/oeqa/controllers/``. + +Selecting SystemdbootTarget +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If you did not set ``TEST_TARGET`` to "SystemdbootTarget", then you do +not need any information in this section. You can skip down to the +"`Running Tests <#qemu-image-running-tests>`__" section. + +If you did set ``TEST_TARGET`` to "SystemdbootTarget", you also need to +perform a one-time setup of your master image by doing the following: + +1. *Set EFI_PROVIDER:* Be sure that ``EFI_PROVIDER`` is as follows: + :: + + EFI_PROVIDER = "systemd-boot" + +2. *Build the master image:* Build the ``core-image-testmaster`` image. + The ``core-image-testmaster`` recipe is provided as an example for a + "master" image and you can customize the image recipe as you would + any other recipe. + + Here are the image recipe requirements: + + - Inherits ``core-image`` so that kernel modules are installed. + + - Installs normal linux utilities not busybox ones (e.g. ``bash``, + ``coreutils``, ``tar``, ``gzip``, and ``kmod``). + + - Uses a custom Initial RAM Disk (initramfs) image with a custom + installer. A normal image that you can install usually creates a + single rootfs partition. This image uses another installer that + creates a specific partition layout. Not all Board Support + Packages (BSPs) can use an installer. For such cases, you need to + manually create the following partition layout on the target: + + - First partition mounted under ``/boot``, labeled "boot". + + - The main rootfs partition where this image gets installed, + which is mounted under ``/``. + + - Another partition labeled "testrootfs" where test images get + deployed. + +3. *Install image:* Install the image that you just built on the target + system. + +The final thing you need to do when setting ``TEST_TARGET`` to +"SystemdbootTarget" is to set up the test image: + +1. *Set up your local.conf file:* Make sure you have the following + statements in your ``local.conf`` file: + :: + + IMAGE_FSTYPES += "tar.gz" + INHERIT += "testimage" + TEST_TARGET = "SystemdbootTarget" + TEST_TARGET_IP = "192.168.2.3" + +2. *Build your test image:* Use BitBake to build the image: + :: + + $ bitbake core-image-sato + +Power Control +~~~~~~~~~~~~~ + +For most hardware targets other than "simpleremote", you can control +power: + +- You can use ``TEST_POWERCONTROL_CMD`` together with + ``TEST_POWERCONTROL_EXTRA_ARGS`` as a command that runs on the host + and does power cycling. The test code passes one argument to that + command: off, on or cycle (off then on). Here is an example that + could appear in your ``local.conf`` file: + :: + + TEST_POWERCONTROL_CMD = "powercontrol.exp test 10.11.12.1 nuc1" + + In this example, the expect + script does the following: + + .. code-block:: shell + + ssh test@10.11.12.1 "pyctl nuc1 arg" + + It then runs a Python script that controls power for a label called + ``nuc1``. + + .. note:: + + You need to customize ``TEST_POWERCONTROL_CMD`` and + ``TEST_POWERCONTROL_EXTRA_ARGS`` for your own setup. The one requirement + is that it accepts "on", "off", and "cycle" as the last argument. + +- When no command is defined, it connects to the device over SSH and + uses the classic reboot command to reboot the device. Classic reboot + is fine as long as the machine actually reboots (i.e. the SSH test + has not failed). It is useful for scenarios where you have a simple + setup, typically with a single board, and where some manual + interaction is okay from time to time. + +If you have no hardware to automatically perform power control but still +wish to experiment with automated hardware testing, you can use the +``dialog-power-control`` script that shows a dialog prompting you to perform +the required power action. This script requires either KDialog or Zenity +to be installed. To use this script, set the +:term:`TEST_POWERCONTROL_CMD` +variable as follows: +:: + + TEST_POWERCONTROL_CMD = "${COREBASE}/scripts/contrib/dialog-power-control" + +Serial Console Connection +~~~~~~~~~~~~~~~~~~~~~~~~~ + +For test target classes requiring a serial console to interact with the +bootloader (e.g. BeagleBoneTarget, EdgeRouterTarget, and GrubTarget), +you need to specify a command to use to connect to the serial console of +the target machine by using the +:term:`TEST_SERIALCONTROL_CMD` +variable and optionally the +:term:`TEST_SERIALCONTROL_EXTRA_ARGS` +variable. + +These cases could be a serial terminal program if the machine is +connected to a local serial port, or a ``telnet`` or ``ssh`` command +connecting to a remote console server. Regardless of the case, the +command simply needs to connect to the serial console and forward that +connection to standard input and output as any normal terminal program +does. For example, to use the picocom terminal program on serial device +``/dev/ttyUSB0`` at 115200bps, you would set the variable as follows: +:: + + TEST_SERIALCONTROL_CMD = "picocom /dev/ttyUSB0 -b 115200" + +For local +devices where the serial port device disappears when the device reboots, +an additional "serdevtry" wrapper script is provided. To use this +wrapper, simply prefix the terminal command with +``${COREBASE}/scripts/contrib/serdevtry``: +:: + + TEST_SERIALCONTROL_CMD = "${COREBASE}/scripts/contrib/serdevtry picocom -b 115200 /dev/ttyUSB0" + +Running Tests +------------- + +You can start the tests automatically or manually: + +- *Automatically running tests:* To run the tests automatically after + the OpenEmbedded build system successfully creates an image, first + set the + :term:`TESTIMAGE_AUTO` + variable to "1" in your ``local.conf`` file in the + :term:`Build Directory`: + :: + + TESTIMAGE_AUTO = "1" + + Next, build your image. If the image successfully builds, the + tests run: + :: + + bitbake core-image-sato + +- *Manually running tests:* To manually run the tests, first globally + inherit the + :ref:`testimage <ref-classes-testimage*>` class + by editing your ``local.conf`` file: + :: + + INHERIT += "testimage" + + Next, use BitBake to run the tests: + :: + + bitbake -c testimage image + +All test files reside in ``meta/lib/oeqa/runtime`` in the +:term:`Source Directory`. A test name maps +directly to a Python module. Each test module may contain a number of +individual tests. Tests are usually grouped together by the area tested +(e.g tests for systemd reside in ``meta/lib/oeqa/runtime/systemd.py``). + +You can add tests to any layer provided you place them in the proper +area and you extend :term:`BBPATH` in +the ``local.conf`` file as normal. Be sure that tests reside in +``layer/lib/oeqa/runtime``. + +.. note:: + + Be sure that module names do not collide with module names used in + the default set of test modules in ``meta/lib/oeqa/runtime``. + +You can change the set of tests run by appending or overriding +:term:`TEST_SUITES` variable in +``local.conf``. Each name in ``TEST_SUITES`` represents a required test +for the image. Test modules named within ``TEST_SUITES`` cannot be +skipped even if a test is not suitable for an image (e.g. running the +RPM tests on an image without ``rpm``). Appending "auto" to +``TEST_SUITES`` causes the build system to try to run all tests that are +suitable for the image (i.e. each test module may elect to skip itself). + +The order you list tests in ``TEST_SUITES`` is important and influences +test dependencies. Consequently, tests that depend on other tests should +be added after the test on which they depend. For example, since the +``ssh`` test depends on the ``ping`` test, "ssh" needs to come after +"ping" in the list. The test class provides no re-ordering or dependency +handling. + +.. note:: + + Each module can have multiple classes with multiple test methods. + And, Python ``unittest`` rules apply. + +Here are some things to keep in mind when running tests: + +- The default tests for the image are defined as: + :: + + DEFAULT_TEST_SUITES_pn-image = "ping ssh df connman syslog xorg scp vnc date rpm dnf dmesg" + +- Add your own test to the list of the by using the following: + :: + + TEST_SUITES_append = " mytest" + +- Run a specific list of tests as follows: + :: + + TEST_SUITES = "test1 test2 test3" + + Remember, order is important. Be sure to place a test that is + dependent on another test later in the order. + +Exporting Tests +--------------- + +You can export tests so that they can run independently of the build +system. Exporting tests is required if you want to be able to hand the +test execution off to a scheduler. You can only export tests that are +defined in :term:`TEST_SUITES`. + +If your image is already built, make sure the following are set in your +``local.conf`` file: +:: + + INHERIT += "testexport" + TEST_TARGET_IP = "IP-address-for-the-test-target" + TEST_SERVER_IP = "IP-address-for-the-test-server" + +You can then export the tests with the +following BitBake command form: +:: + + $ bitbake image -c testexport + +Exporting the tests places them in the +:term:`Build Directory` in +``tmp/testexport/``\ image, which is controlled by the +``TEST_EXPORT_DIR`` variable. + +You can now run the tests outside of the build environment: +:: + + $ cd tmp/testexport/image + $ ./runexported.py testdata.json + +Here is a complete example that shows IP addresses and uses the +``core-image-sato`` image: +:: + + INHERIT += "testexport" + TEST_TARGET_IP = "192.168.7.2" + TEST_SERVER_IP = "192.168.7.1" + +Use BitBake to export the tests: +:: + + $ bitbake core-image-sato -c testexport + +Run the tests outside of +the build environment using the following: +:: + + $ cd tmp/testexport/core-image-sato + $ ./runexported.py testdata.json + +Writing New Tests +----------------- + +As mentioned previously, all new test files need to be in the proper +place for the build system to find them. New tests for additional +functionality outside of the core should be added to the layer that adds +the functionality, in ``layer/lib/oeqa/runtime`` (as long as +:term:`BBPATH` is extended in the +layer's ``layer.conf`` file as normal). Just remember the following: + +- Filenames need to map directly to test (module) names. + +- Do not use module names that collide with existing core tests. + +- Minimally, an empty ``__init__.py`` file must exist in the runtime + directory. + +To create a new test, start by copying an existing module (e.g. +``syslog.py`` or ``gcc.py`` are good ones to use). Test modules can use +code from ``meta/lib/oeqa/utils``, which are helper classes. + +.. note:: + + Structure shell commands such that you rely on them and they return a + single code for success. Be aware that sometimes you will need to + parse the output. See the ``df.py`` and ``date.py`` modules for examples. + +You will notice that all test classes inherit ``oeRuntimeTest``, which +is found in ``meta/lib/oetest.py``. This base class offers some helper +attributes, which are described in the following sections: + +Class Methods +~~~~~~~~~~~~~ + +Class methods are as follows: + +- *hasPackage(pkg):* Returns "True" if ``pkg`` is in the installed + package list of the image, which is based on the manifest file that + is generated during the ``do_rootfs`` task. + +- *hasFeature(feature):* Returns "True" if the feature is in + :term:`IMAGE_FEATURES` or + :term:`DISTRO_FEATURES`. + +Class Attributes +~~~~~~~~~~~~~~~~ + +Class attributes are as follows: + +- *pscmd:* Equals "ps -ef" if ``procps`` is installed in the image. + Otherwise, ``pscmd`` equals "ps" (busybox). + +- *tc:* The called test context, which gives access to the + following attributes: + + - *d:* The BitBake datastore, which allows you to use stuff such + as ``oeRuntimeTest.tc.d.getVar("VIRTUAL-RUNTIME_init_manager")``. + + - *testslist and testsrequired:* Used internally. The tests + do not need these. + + - *filesdir:* The absolute path to + ``meta/lib/oeqa/runtime/files``, which contains helper files for + tests meant for copying on the target such as small files written + in C for compilation. + + - *target:* The target controller object used to deploy and + start an image on a particular target (e.g. Qemu, SimpleRemote, + and SystemdbootTarget). Tests usually use the following: + + - *ip:* The target's IP address. + + - *server_ip:* The host's IP address, which is usually used + by the DNF test suite. + + - *run(cmd, timeout=None):* The single, most used method. + This command is a wrapper for: ``ssh root@host "cmd"``. The + command returns a tuple: (status, output), which are what their + names imply - the return code of "cmd" and whatever output it + produces. The optional timeout argument represents the number + of seconds the test should wait for "cmd" to return. If the + argument is "None", the test uses the default instance's + timeout period, which is 300 seconds. If the argument is "0", + the test runs until the command returns. + + - *copy_to(localpath, remotepath):* + ``scp localpath root@ip:remotepath``. + + - *copy_from(remotepath, localpath):* + ``scp root@host:remotepath localpath``. + +Instance Attributes +~~~~~~~~~~~~~~~~~~~ + +A single instance attribute exists, which is ``target``. The ``target`` +instance attribute is identical to the class attribute of the same name, +which is described in the previous section. This attribute exists as +both an instance and class attribute so tests can use +``self.target.run(cmd)`` in instance methods instead of +``oeRuntimeTest.tc.target.run(cmd)``. + +Installing Packages in the DUT Without the Package Manager +---------------------------------------------------------- + +When a test requires a package built by BitBake, it is possible to +install that package. Installing the package does not require a package +manager be installed in the device under test (DUT). It does, however, +require an SSH connection and the target must be using the +``sshcontrol`` class. + +.. note:: + + This method uses ``scp`` to copy files from the host to the target, which + causes permissions and special attributes to be lost. + +A JSON file is used to define the packages needed by a test. This file +must be in the same path as the file used to define the tests. +Furthermore, the filename must map directly to the test module name with +a ``.json`` extension. + +The JSON file must include an object with the test name as keys of an +object or an array. This object (or array of objects) uses the following +data: + +- "pkg" - A mandatory string that is the name of the package to be + installed. + +- "rm" - An optional boolean, which defaults to "false", that specifies + to remove the package after the test. + +- "extract" - An optional boolean, which defaults to "false", that + specifies if the package must be extracted from the package format. + When set to "true", the package is not automatically installed into + the DUT. + +Following is an example JSON file that handles test "foo" installing +package "bar" and test "foobar" installing packages "foo" and "bar". +Once the test is complete, the packages are removed from the DUT. +:: + + { + "foo": { + "pkg": "bar" + }, + "foobar": [ + { + "pkg": "foo", + "rm": true + }, + { + "pkg": "bar", + "rm": true + } + ] + } + +Debugging Tools and Techniques +============================== + +The exact method for debugging build failures depends on the nature of +the problem and on the system's area from which the bug originates. +Standard debugging practices such as comparison against the last known +working version with examination of the changes and the re-application +of steps to identify the one causing the problem are valid for the Yocto +Project just as they are for any other system. Even though it is +impossible to detail every possible potential failure, this section +provides some general tips to aid in debugging given a variety of +situations. + +.. note:: + + A useful feature for debugging is the error reporting tool. + Configuring the Yocto Project to use this tool causes the + OpenEmbedded build system to produce error reporting commands as part + of the console output. You can enter the commands after the build + completes to log error information into a common database, that can + help you figure out what might be going wrong. For information on how + to enable and use this feature, see the + ":ref:`dev-manual/common-tasks:using the error reporting tool`" + section. + +The following list shows the debugging topics in the remainder of this +section: + +- "`Viewing Logs from Failed + Tasks <#dev-debugging-viewing-logs-from-failed-tasks>`__" describes + how to find and view logs from tasks that failed during the build + process. + +- "`Viewing Variable + Values <#dev-debugging-viewing-variable-values>`__" describes how to + use the BitBake ``-e`` option to examine variable values after a + recipe has been parsed. + +- ":ref:`dev-manual/common-tasks:viewing package information with \`\`oe-pkgdata-util\`\``" + describes how to use the ``oe-pkgdata-util`` utility to query + :term:`PKGDATA_DIR` and + display package-related information for built packages. + +- "`Viewing Dependencies Between Recipes and + Tasks <#dev-viewing-dependencies-between-recipes-and-tasks>`__" + describes how to use the BitBake ``-g`` option to display recipe + dependency information used during the build. + +- "`Viewing Task Variable + Dependencies <#dev-viewing-task-variable-dependencies>`__" describes + how to use the ``bitbake-dumpsig`` command in conjunction with key + subdirectories in the + :term:`Build Directory` to determine + variable dependencies. + +- "`Running Specific Tasks <#dev-debugging-taskrunning>`__" describes + how to use several BitBake options (e.g. ``-c``, ``-C``, and ``-f``) + to run specific tasks in the build chain. It can be useful to run + tasks "out-of-order" when trying isolate build issues. + +- "`General BitBake Problems <#dev-debugging-bitbake>`__" describes how + to use BitBake's ``-D`` debug output option to reveal more about what + BitBake is doing during the build. + +- "`Building with No Dependencies <#dev-debugging-buildfile>`__" + describes how to use the BitBake ``-b`` option to build a recipe + while ignoring dependencies. + +- "`Recipe Logging Mechanisms <#recipe-logging-mechanisms>`__" + describes how to use the many recipe logging functions to produce + debugging output and report errors and warnings. + +- "`Debugging Parallel Make Races <#debugging-parallel-make-races>`__" + describes how to debug situations where the build consists of several + parts that are run simultaneously and when the output or result of + one part is not ready for use with a different part of the build that + depends on that output. + +- "`Debugging With the GNU Project Debugger (GDB) + Remotely <#platdev-gdb-remotedebug>`__" describes how to use GDB to + allow you to examine running programs, which can help you fix + problems. + +- "`Debugging with the GNU Project Debugger (GDB) on the + Target <#debugging-with-the-gnu-project-debugger-gdb-on-the-target>`__" + describes how to use GDB directly on target hardware for debugging. + +- "`Other Debugging Tips <#dev-other-debugging-others>`__" describes + miscellaneous debugging tips that can be useful. + +Viewing Logs from Failed Tasks +------------------------------ + +You can find the log for a task in the file +``${``\ :term:`WORKDIR`\ ``}/temp/log.do_``\ `taskname`. +For example, the log for the +:ref:`ref-tasks-compile` task of the +QEMU minimal image for the x86 machine (``qemux86``) might be in +``tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile``. +To see the commands :term:`BitBake` ran +to generate a log, look at the corresponding ``run.do_``\ `taskname` file +in the same directory. + +``log.do_``\ `taskname` and ``run.do_``\ `taskname` are actually symbolic +links to ``log.do_``\ `taskname`\ ``.``\ `pid` and +``log.run_``\ `taskname`\ ``.``\ `pid`, where `pid` is the PID the task had +when it ran. The symlinks always point to the files corresponding to the +most recent run. + +Viewing Variable Values +----------------------- + +Sometimes you need to know the value of a variable as a result of +BitBake's parsing step. This could be because some unexpected behavior +occurred in your project. Perhaps an attempt to :ref:`modify a variable +<bitbake:bitbake-user-manual/bitbake-user-manual-metadata:modifying existing +variables>` did not work out as expected. + +BitBake's ``-e`` option is used to display variable values after +parsing. The following command displays the variable values after the +configuration files (i.e. ``local.conf``, ``bblayers.conf``, +``bitbake.conf`` and so forth) have been parsed: +:: + + $ bitbake -e + +The following command displays variable values after a specific recipe has +been parsed. The variables include those from the configuration as well: +:: + + $ bitbake -e recipename + +.. note:: + + Each recipe has its own private set of variables (datastore). + Internally, after parsing the configuration, a copy of the resulting + datastore is made prior to parsing each recipe. This copying implies + that variables set in one recipe will not be visible to other + recipes. + + Likewise, each task within a recipe gets a private datastore based on + the recipe datastore, which means that variables set within one task + will not be visible to other tasks. + +In the output of ``bitbake -e``, each variable is preceded by a +description of how the variable got its value, including temporary +values that were later overridden. This description also includes +variable flags (varflags) set on the variable. The output can be very +helpful during debugging. + +Variables that are exported to the environment are preceded by +``export`` in the output of ``bitbake -e``. See the following example: +:: + + export CC="i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/ulf/poky/build/tmp/sysroots/qemux86" + +In addition to variable values, the output of the ``bitbake -e`` and +``bitbake -e`` recipe commands includes the following information: + +- The output starts with a tree listing all configuration files and + classes included globally, recursively listing the files they include + or inherit in turn. Much of the behavior of the OpenEmbedded build + system (including the behavior of the :ref:`ref-manual/ref-tasks:normal recipe build tasks`) is + implemented in the + :ref:`base <ref-classes-base>` class and the + classes it inherits, rather than being built into BitBake itself. + +- After the variable values, all functions appear in the output. For + shell functions, variables referenced within the function body are + expanded. If a function has been modified using overrides or using + override-style operators like ``_append`` and ``_prepend``, then the + final assembled function body appears in the output. + +Viewing Package Information with ``oe-pkgdata-util`` +---------------------------------------------------- + +You can use the ``oe-pkgdata-util`` command-line utility to query +:term:`PKGDATA_DIR` and display +various package-related information. When you use the utility, you must +use it to view information on packages that have already been built. + +Following are a few of the available ``oe-pkgdata-util`` subcommands. + +.. note:: + + You can use the standard \* and ? globbing wildcards as part of + package names and paths. + +- ``oe-pkgdata-util list-pkgs [pattern]``: Lists all packages + that have been built, optionally limiting the match to packages that + match pattern. + +- ``oe-pkgdata-util list-pkg-files package ...``: Lists the + files and directories contained in the given packages. + + .. note:: + + A different way to view the contents of a package is to look at + the + ``${``\ :term:`WORKDIR`\ ``}/packages-split`` + directory of the recipe that generates the package. This directory + is created by the + :ref:`ref-tasks-package` task + and has one subdirectory for each package the recipe generates, + which contains the files stored in that package. + + If you want to inspect the ``${WORKDIR}/packages-split`` + directory, make sure that + :ref:`rm_work <ref-classes-rm-work>` is not + enabled when you build the recipe. + +- ``oe-pkgdata-util find-path path ...``: Lists the names of + the packages that contain the given paths. For example, the following + tells us that ``/usr/share/man/man1/make.1`` is contained in the + ``make-doc`` package: + :: + + $ oe-pkgdata-util find-path /usr/share/man/man1/make.1 + make-doc: /usr/share/man/man1/make.1 + +- ``oe-pkgdata-util lookup-recipe package ...``: Lists the name + of the recipes that produce the given packages. + +For more information on the ``oe-pkgdata-util`` command, use the help +facility: +:: + + $ oe-pkgdata-util --help + $ oe-pkgdata-util subcommand --help + +Viewing Dependencies Between Recipes and Tasks +---------------------------------------------- + +Sometimes it can be hard to see why BitBake wants to build other recipes +before the one you have specified. Dependency information can help you +understand why a recipe is built. + +To generate dependency information for a recipe, run the following +command: +:: + + $ bitbake -g recipename + +This command writes the following files in the current directory: + +- ``pn-buildlist``: A list of recipes/targets involved in building + `recipename`. "Involved" here means that at least one task from the + recipe needs to run when building `recipename` from scratch. Targets + that are in + :term:`ASSUME_PROVIDED` + are not listed. + +- ``task-depends.dot``: A graph showing dependencies between tasks. + +The graphs are in +`DOT <https://en.wikipedia.org/wiki/DOT_%28graph_description_language%29>`__ +format and can be converted to images (e.g. using the ``dot`` tool from +`Graphviz <https://www.graphviz.org/>`__). + +.. note:: + + - DOT files use a plain text format. The graphs generated using the + ``bitbake -g`` command are often so large as to be difficult to + read without special pruning (e.g. with Bitbake's ``-I`` option) + and processing. Despite the form and size of the graphs, the + corresponding ``.dot`` files can still be possible to read and + provide useful information. + + As an example, the ``task-depends.dot`` file contains lines such + as the following: + :: + + "libxslt.do_configure" -> "libxml2.do_populate_sysroot" + + The above example line reveals that the + :ref:`ref-tasks-configure` + task in ``libxslt`` depends on the + :ref:`ref-tasks-populate_sysroot` + task in ``libxml2``, which is a normal + :term:`DEPENDS` dependency + between the two recipes. + + - For an example of how ``.dot`` files can be processed, see the + ``scripts/contrib/graph-tool`` Python script, which finds and + displays paths between graph nodes. + +You can use a different method to view dependency information by using +the following command: +:: + + $ bitbake -g -u taskexp recipename + +This command +displays a GUI window from which you can view build-time and runtime +dependencies for the recipes involved in building recipename. + +Viewing Task Variable Dependencies +---------------------------------- + +As mentioned in the +":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-execution:checksums (signatures)`" section of the BitBake +User Manual, BitBake tries to automatically determine what variables a +task depends on so that it can rerun the task if any values of the +variables change. This determination is usually reliable. However, if +you do things like construct variable names at runtime, then you might +have to manually declare dependencies on those variables using +``vardeps`` as described in the +":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags`" section of the BitBake +User Manual. + +If you are unsure whether a variable dependency is being picked up +automatically for a given task, you can list the variable dependencies +BitBake has determined by doing the following: + +1. Build the recipe containing the task: +:: + + $ bitbake recipename + +2. Inside the :term:`STAMPS_DIR` + directory, find the signature data (``sigdata``) file that + corresponds to the task. The ``sigdata`` files contain a pickled + Python database of all the metadata that went into creating the input + checksum for the task. As an example, for the + :ref:`ref-tasks-fetch` task of the + ``db`` recipe, the ``sigdata`` file might be found in the following + location: + :: + + ${BUILDDIR}/tmp/stamps/i586-poky-linux/db/6.0.30-r1.do_fetch.sigdata.7c048c18222b16ff0bcee2000ef648b1 + + For tasks that are accelerated through the shared state + (:ref:`sstate <overview-manual/overview-manual-concepts:shared state cache>`) cache, an + additional ``siginfo`` file is written into + :term:`SSTATE_DIR` along with + the cached task output. The ``siginfo`` files contain exactly the + same information as ``sigdata`` files. + +3. Run ``bitbake-dumpsig`` on the ``sigdata`` or ``siginfo`` file. Here + is an example: + :: + + $ bitbake-dumpsig ${BUILDDIR}/tmp/stamps/i586-poky-linux/db/6.0.30-r1.do_fetch.sigdata.7c048c18222b16ff0bcee2000ef648b1 + + In the output of the above command, you will find a line like the + following, which lists all the (inferred) variable dependencies for + the task. This list also includes indirect dependencies from + variables depending on other variables, recursively. + :: + + Task dependencies: ['PV', 'SRCREV', 'SRC_URI', 'SRC_URI[md5sum]', 'SRC_URI[sha256sum]', 'base_do_fetch'] + + .. note:: + + Functions (e.g. ``base_do_fetch``) also count as variable dependencies. + These functions in turn depend on the variables they reference. + + The output of ``bitbake-dumpsig`` also includes the value each + variable had, a list of dependencies for each variable, and + :term:`bitbake:BB_HASHBASE_WHITELIST` + information. + +There is also a ``bitbake-diffsigs`` command for comparing two +``siginfo`` or ``sigdata`` files. This command can be helpful when +trying to figure out what changed between two versions of a task. If you +call ``bitbake-diffsigs`` with just one file, the command behaves like +``bitbake-dumpsig``. + +You can also use BitBake to dump out the signature construction +information without executing tasks by using either of the following +BitBake command-line options: +:: + + ‐‐dump-signatures=SIGNATURE_HANDLER + -S SIGNATURE_HANDLER + + +.. note:: + + Two common values for `SIGNATURE_HANDLER` are "none" and "printdiff", which + dump only the signature or compare the dumped signature with the cached one, + respectively. + +Using BitBake with either of these options causes BitBake to dump out +``sigdata`` files in the ``stamps`` directory for every task it would +have executed instead of building the specified target package. + +Viewing Metadata Used to Create the Input Signature of a Shared State Task +-------------------------------------------------------------------------- + +Seeing what metadata went into creating the input signature of a shared +state (sstate) task can be a useful debugging aid. This information is +available in signature information (``siginfo``) files in +:term:`SSTATE_DIR`. For +information on how to view and interpret information in ``siginfo`` +files, see the "`Viewing Task Variable +Dependencies <#dev-viewing-task-variable-dependencies>`__" section. + +For conceptual information on shared state, see the +":ref:`overview-manual/overview-manual-concepts:shared state`" +section in the Yocto Project Overview and Concepts Manual. + +Invalidating Shared State to Force a Task to Run +------------------------------------------------ + +The OpenEmbedded build system uses +:ref:`checksums <overview-manual/overview-manual-concepts:checksums (signatures)>` and +:ref:`overview-manual/overview-manual-concepts:shared state` cache to avoid unnecessarily +rebuilding tasks. Collectively, this scheme is known as "shared state +code". + +As with all schemes, this one has some drawbacks. It is possible that +you could make implicit changes to your code that the checksum +calculations do not take into account. These implicit changes affect a +task's output but do not trigger the shared state code into rebuilding a +recipe. Consider an example during which a tool changes its output. +Assume that the output of ``rpmdeps`` changes. The result of the change +should be that all the ``package`` and ``package_write_rpm`` shared +state cache items become invalid. However, because the change to the +output is external to the code and therefore implicit, the associated +shared state cache items do not become invalidated. In this case, the +build process uses the cached items rather than running the task again. +Obviously, these types of implicit changes can cause problems. + +To avoid these problems during the build, you need to understand the +effects of any changes you make. Realize that changes you make directly +to a function are automatically factored into the checksum calculation. +Thus, these explicit changes invalidate the associated area of shared +state cache. However, you need to be aware of any implicit changes that +are not obvious changes to the code and could affect the output of a +given task. + +When you identify an implicit change, you can easily take steps to +invalidate the cache and force the tasks to run. The steps you can take +are as simple as changing a function's comments in the source code. For +example, to invalidate package shared state files, change the comment +statements of +:ref:`ref-tasks-package` or the +comments of one of the functions it calls. Even though the change is +purely cosmetic, it causes the checksum to be recalculated and forces +the build system to run the task again. + +.. note:: + + For an example of a commit that makes a cosmetic change to invalidate + shared state, see this + :yocto_git:`commit </poky/commit/meta/classes/package.bbclass?id=737f8bbb4f27b4837047cb9b4fbfe01dfde36d54>`. + +Running Specific Tasks +---------------------- + +Any given recipe consists of a set of tasks. The standard BitBake +behavior in most cases is: ``do_fetch``, ``do_unpack``, ``do_patch``, +``do_configure``, ``do_compile``, ``do_install``, ``do_package``, +``do_package_write_*``, and ``do_build``. The default task is +``do_build`` and any tasks on which it depends build first. Some tasks, +such as ``do_devshell``, are not part of the default build chain. If you +wish to run a task that is not part of the default build chain, you can +use the ``-c`` option in BitBake. Here is an example: +:: + + $ bitbake matchbox-desktop -c devshell + +The ``-c`` option respects task dependencies, which means that all other +tasks (including tasks from other recipes) that the specified task +depends on will be run before the task. Even when you manually specify a +task to run with ``-c``, BitBake will only run the task if it considers +it "out of date". See the +":ref:`overview-manual/overview-manual-concepts:stamp files and the rerunning of tasks`" +section in the Yocto Project Overview and Concepts Manual for how +BitBake determines whether a task is "out of date". + +If you want to force an up-to-date task to be rerun (e.g. because you +made manual modifications to the recipe's +:term:`WORKDIR` that you want to try +out), then you can use the ``-f`` option. + +.. note:: + + The reason ``-f`` is never required when running the + :ref:`ref-tasks-devshell` task is because the + [\ :ref:`nostamp <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ] + variable flag is already set for the task. + +The following example shows one way you can use the ``-f`` option: +:: + + $ bitbake matchbox-desktop + . + . + make some changes to the source code in the work directory + . + . + $ bitbake matchbox-desktop -c compile -f + $ bitbake matchbox-desktop + +This sequence first builds and then recompiles ``matchbox-desktop``. The +last command reruns all tasks (basically the packaging tasks) after the +compile. BitBake recognizes that the ``do_compile`` task was rerun and +therefore understands that the other tasks also need to be run again. + +Another, shorter way to rerun a task and all +:ref:`ref-manual/ref-tasks:normal recipe build tasks` +that depend on it is to use the ``-C`` option. + +.. note:: + + This option is upper-cased and is separate from the ``-c`` + option, which is lower-cased. + +Using this option invalidates the given task and then runs the +:ref:`ref-tasks-build` task, which is +the default task if no task is given, and the tasks on which it depends. +You could replace the final two commands in the previous example with +the following single command: +:: + + $ bitbake matchbox-desktop -C compile + +Internally, the ``-f`` and ``-C`` options work by tainting (modifying) +the input checksum of the specified task. This tainting indirectly +causes the task and its dependent tasks to be rerun through the normal +task dependency mechanisms. + +.. note:: + + BitBake explicitly keeps track of which tasks have been tainted in + this fashion, and will print warnings such as the following for + builds involving such tasks: + + .. code-block:: none + + WARNING: /home/ulf/poky/meta/recipes-sato/matchbox-desktop/matchbox-desktop_2.1.bb.do_compile is tainted from a forced run + + + The purpose of the warning is to let you know that the work directory + and build output might not be in the clean state they would be in for + a "normal" build, depending on what actions you took. To get rid of + such warnings, you can remove the work directory and rebuild the + recipe, as follows: + :: + + $ bitbake matchbox-desktop -c clean + $ bitbake matchbox-desktop + + +You can view a list of tasks in a given package by running the +``do_listtasks`` task as follows: +:: + + $ bitbake matchbox-desktop -c listtasks + +The results appear as output to the console and are also in +the file ``${WORKDIR}/temp/log.do_listtasks``. + +General BitBake Problems +------------------------ + +You can see debug output from BitBake by using the ``-D`` option. The +debug output gives more information about what BitBake is doing and the +reason behind it. Each ``-D`` option you use increases the logging +level. The most common usage is ``-DDD``. + +The output from ``bitbake -DDD -v targetname`` can reveal why BitBake +chose a certain version of a package or why BitBake picked a certain +provider. This command could also help you in a situation where you +think BitBake did something unexpected. + +Building with No Dependencies +----------------------------- + +To build a specific recipe (``.bb`` file), you can use the following +command form: +:: + + $ bitbake -b somepath/somerecipe.bb + +This command form does +not check for dependencies. Consequently, you should use it only when +you know existing dependencies have been met. + +.. note:: + + You can also specify fragments of the filename. In this case, BitBake + checks for a unique match. + +Recipe Logging Mechanisms +------------------------- + +The Yocto Project provides several logging functions for producing +debugging output and reporting errors and warnings. For Python +functions, the following logging functions exist. All of these functions +log to ``${T}/log.do_``\ `task`, and can also log to standard output +(stdout) with the right settings: + +- ``bb.plain(msg)``: Writes msg as is to the log while also + logging to stdout. + +- ``bb.note(msg)``: Writes "NOTE: msg" to the log. Also logs to + stdout if BitBake is called with "-v". + +- ``bb.debug(level, msg)``: Writes "DEBUG: msg" to the + log. Also logs to stdout if the log level is greater than or equal to + level. See the ":ref:`-D <bitbake:bitbake-user-manual/bitbake-user-manual-intro:usage and syntax>`" option + in the BitBake User Manual for more information. + +- ``bb.warn(msg)``: Writes "WARNING: msg" to the log while also + logging to stdout. + +- ``bb.error(msg)``: Writes "ERROR: msg" to the log while also + logging to standard out (stdout). + + .. note:: + + Calling this function does not cause the task to fail. + +- ``bb.fatal(``\ msg\ ``)``: This logging function is similar to + ``bb.error(``\ msg\ ``)`` but also causes the calling task to fail. + + .. note:: + + ``bb.fatal()`` raises an exception, which means you do not need to put a + "return" statement after the function. + +The same logging functions are also available in shell functions, under +the names ``bbplain``, ``bbnote``, ``bbdebug``, ``bbwarn``, ``bberror``, +and ``bbfatal``. The +:ref:`logging <ref-classes-logging>` class +implements these functions. See that class in the ``meta/classes`` +folder of the :term:`Source Directory` for information. + +Logging With Python +~~~~~~~~~~~~~~~~~~~ + +When creating recipes using Python and inserting code that handles build +logs, keep in mind the goal is to have informative logs while keeping +the console as "silent" as possible. Also, if you want status messages +in the log, use the "debug" loglevel. + +Following is an example written in Python. The code handles logging for +a function that determines the number of tasks needed to be run. See the +":ref:`ref-tasks-listtasks`" +section for additional information: +:: + + python do_listtasks() { + bb.debug(2, "Starting to figure out the task list") + if noteworthy_condition: + bb.note("There are 47 tasks to run") + bb.debug(2, "Got to point xyz") + if warning_trigger: + bb.warn("Detected warning_trigger, this might be a problem later.") + if recoverable_error: + bb.error("Hit recoverable_error, you really need to fix this!") + if fatal_error: + bb.fatal("fatal_error detected, unable to print the task list") + bb.plain("The tasks present are abc") + bb.debug(2, "Finished figuring out the tasklist") + } + +Logging With Bash +~~~~~~~~~~~~~~~~~ + +When creating recipes using Bash and inserting code that handles build +logs, you have the same goals - informative with minimal console output. +The syntax you use for recipes written in Bash is similar to that of +recipes written in Python described in the previous section. + +Following is an example written in Bash. The code logs the progress of +the ``do_my_function`` function. +:: + + do_my_function() { + bbdebug 2 "Running do_my_function" + if [ exceptional_condition ]; then + bbnote "Hit exceptional_condition" + fi + bbdebug 2 "Got to point xyz" + if [ warning_trigger ]; then + bbwarn "Detected warning_trigger, this might cause a problem later." + fi + if [ recoverable_error ]; then + bberror "Hit recoverable_error, correcting" + fi + if [ fatal_error ]; then + bbfatal "fatal_error detected" + fi + bbdebug 2 "Completed do_my_function" + } + + +Debugging Parallel Make Races +----------------------------- + +A parallel ``make`` race occurs when the build consists of several parts +that are run simultaneously and a situation occurs when the output or +result of one part is not ready for use with a different part of the +build that depends on that output. Parallel make races are annoying and +can sometimes be difficult to reproduce and fix. However, some simple +tips and tricks exist that can help you debug and fix them. This section +presents a real-world example of an error encountered on the Yocto +Project autobuilder and the process used to fix it. + +.. note:: + + If you cannot properly fix a ``make`` race condition, you can work around it + by clearing either the :term:`PARALLEL_MAKE` or :term:`PARALLEL_MAKEINST` + variables. + +The Failure +~~~~~~~~~~~ + +For this example, assume that you are building an image that depends on +the "neard" package. And, during the build, BitBake runs into problems +and creates the following output. + +.. note:: + + This example log file has longer lines artificially broken to make + the listing easier to read. + +If you examine the output or the log file, you see the failure during +``make``: + +.. code-block:: none + + | DEBUG: SITE files ['endian-little', 'bit-32', 'ix86-common', 'common-linux', 'common-glibc', 'i586-linux', 'common'] + | DEBUG: Executing shell function do_compile + | NOTE: make -j 16 + | make --no-print-directory all-am + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/types.h include/near/types.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/log.h include/near/log.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/plugin.h include/near/plugin.h + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/tag.h include/near/tag.h + | /bin/mkdir -p include/near + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/adapter.h include/near/adapter.h + | /bin/mkdir -p include/near + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/ndef.h include/near/ndef.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/tlv.h include/near/tlv.h + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/setting.h include/near/setting.h + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | /bin/mkdir -p include/near + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/device.h include/near/device.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/nfc_copy.h include/near/nfc_copy.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/snep.h include/near/snep.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/version.h include/near/version.h + | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/ + 0.14-r0/neard-0.14/include/dbus.h include/near/dbus.h + | ./src/genbuiltin nfctype1 nfctype2 nfctype3 nfctype4 p2p > src/builtin.h + | i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/ + build/build/tmp/sysroots/qemux86 -DHAVE_CONFIG_H -I. -I./include -I./src -I./gdbus -I/home/pokybuild/ + yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/include/glib-2.0 + -I/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/ + lib/glib-2.0/include -I/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/ + tmp/sysroots/qemux86/usr/include/dbus-1.0 -I/home/pokybuild/yocto-autobuilder/yocto-slave/ + nightly-x86/build/build/tmp/sysroots/qemux86/usr/lib/dbus-1.0/include -I/home/pokybuild/yocto-autobuilder/ + yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/include/libnl3 + -DNEAR_PLUGIN_BUILTIN -DPLUGINDIR=\""/usr/lib/near/plugins"\" + -DCONFIGDIR=\""/etc/neard\"" -O2 -pipe -g -feliminate-unused-debug-types -c + -o tools/snep-send.o tools/snep-send.c + | In file included from tools/snep-send.c:16:0: + | tools/../src/near.h:41:23: fatal error: near/dbus.h: No such file or directory + | #include <near/dbus.h> + | ^ + | compilation terminated. + | make[1]: *** [tools/snep-send.o] Error 1 + | make[1]: *** Waiting for unfinished jobs.... + | make: *** [all] Error 2 + | ERROR: oe_runmake failed + +Reproducing the Error +~~~~~~~~~~~~~~~~~~~~~ + +Because race conditions are intermittent, they do not manifest +themselves every time you do the build. In fact, most times the build +will complete without problems even though the potential race condition +exists. Thus, once the error surfaces, you need a way to reproduce it. + +In this example, compiling the "neard" package is causing the problem. +So the first thing to do is build "neard" locally. Before you start the +build, set the +:term:`PARALLEL_MAKE` variable +in your ``local.conf`` file to a high number (e.g. "-j 20"). Using a +high value for ``PARALLEL_MAKE`` increases the chances of the race +condition showing up: +:: + + $ bitbake neard + +Once the local build for "neard" completes, start a ``devshell`` build: +:: + + $ bitbake neard -c devshell + +For information on how to use a +``devshell``, see the "`Using a Development +Shell <#platdev-appdev-devshell>`__" section. + +In the ``devshell``, do the following: +:: + + $ make clean + $ make tools/snep-send.o + +The ``devshell`` commands cause the failure to clearly +be visible. In this case, a missing dependency exists for the "neard" +Makefile target. Here is some abbreviated, sample output with the +missing dependency clearly visible at the end: +:: + + i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/scott-lenovo/...... + . + . + . + tools/snep-send.c + In file included from tools/snep-send.c:16:0: + tools/../src/near.h:41:23: fatal error: near/dbus.h: No such file or directory + #include <near/dbus.h> + ^ + compilation terminated. + make: *** [tools/snep-send.o] Error 1 + $ + + +Creating a Patch for the Fix +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Because there is a missing dependency for the Makefile target, you need +to patch the ``Makefile.am`` file, which is generated from +``Makefile.in``. You can use Quilt to create the patch: +:: + + $ quilt new parallelmake.patch + Patch patches/parallelmake.patch is now on top + $ quilt add Makefile.am + File Makefile.am added to patch patches/parallelmake.patch + +For more information on using Quilt, see the +"`Using Quilt in Your Workflow <#using-a-quilt-workflow>`__" section. + +At this point you need to make the edits to ``Makefile.am`` to add the +missing dependency. For our example, you have to add the following line +to the file: +:: + + tools/snep-send.$(OBJEXT): include/near/dbus.h + +Once you have edited the file, use the ``refresh`` command to create the +patch: +:: + + $ quilt refresh + Refreshed patch patches/parallelmake.patch + +Once +the patch file exists, you need to add it back to the originating recipe +folder. Here is an example assuming a top-level +:term:`Source Directory` named ``poky``: +:: + + $ cp patches/parallelmake.patch poky/meta/recipes-connectivity/neard/neard + +The final thing you need to do to implement the fix in the build is to +update the "neard" recipe (i.e. ``neard-0.14.bb``) so that the +:term:`SRC_URI` statement includes +the patch file. The recipe file is in the folder above the patch. Here +is what the edited ``SRC_URI`` statement would look like: +:: + + SRC_URI = "${KERNELORG_MIRROR}/linux/network/nfc/${BPN}-${PV}.tar.xz \ + file://neard.in \ + file://neard.service.in \ + file://parallelmake.patch \ + " + +With the patch complete and moved to the correct folder and the +``SRC_URI`` statement updated, you can exit the ``devshell``: +:: + + $ exit + +Testing the Build +~~~~~~~~~~~~~~~~~ + +With everything in place, you can get back to trying the build again +locally: +:: + + $ bitbake neard + +This build should succeed. + +Now you can open up a ``devshell`` again and repeat the clean and make +operations as follows: +:: + + $ bitbake neard -c devshell + $ make clean + $ make tools/snep-send.o + +The build should work without issue. + +As with all solved problems, if they originated upstream, you need to +submit the fix for the recipe in OE-Core and upstream so that the +problem is taken care of at its source. See the "`Submitting a Change to +the Yocto Project <#how-to-submit-a-change>`__" section for more +information. + +Debugging With the GNU Project Debugger (GDB) Remotely +------------------------------------------------------ + +GDB allows you to examine running programs, which in turn helps you to +understand and fix problems. It also allows you to perform post-mortem +style analysis of program crashes. GDB is available as a package within +the Yocto Project and is installed in SDK images by default. See the +":ref:`ref-manual/ref-images:Images`" chapter in the Yocto +Project Reference Manual for a description of these images. You can find +information on GDB at https://sourceware.org/gdb/. + +.. note:: + + For best results, install debug (``-dbg``) packages for the applications you + are going to debug. Doing so makes extra debug symbols available that give + you more meaningful output. + +Sometimes, due to memory or disk space constraints, it is not possible +to use GDB directly on the remote target to debug applications. These +constraints arise because GDB needs to load the debugging information +and the binaries of the process being debugged. Additionally, GDB needs +to perform many computations to locate information such as function +names, variable names and values, stack traces and so forth - even +before starting the debugging process. These extra computations place +more load on the target system and can alter the characteristics of the +program being debugged. + +To help get past the previously mentioned constraints, you can use +gdbserver, which runs on the remote target and does not load any +debugging information from the debugged process. Instead, a GDB instance +processes the debugging information that is run on a remote computer - +the host GDB. The host GDB then sends control commands to gdbserver to +make it stop or start the debugged program, as well as read or write +memory regions of that debugged program. All the debugging information +loaded and processed as well as all the heavy debugging is done by the +host GDB. Offloading these processes gives the gdbserver running on the +target a chance to remain small and fast. + +Because the host GDB is responsible for loading the debugging +information and for doing the necessary processing to make actual +debugging happen, you have to make sure the host can access the +unstripped binaries complete with their debugging information and also +be sure the target is compiled with no optimizations. The host GDB must +also have local access to all the libraries used by the debugged +program. Because gdbserver does not need any local debugging +information, the binaries on the remote target can remain stripped. +However, the binaries must also be compiled without optimization so they +match the host's binaries. + +To remain consistent with GDB documentation and terminology, the binary +being debugged on the remote target machine is referred to as the +"inferior" binary. For documentation on GDB see the `GDB +site <https://sourceware.org/gdb/documentation/>`__. + +The following steps show you how to debug using the GNU project +debugger. + +1. *Configure your build system to construct the companion debug + filesystem:* + + In your ``local.conf`` file, set the following: + :: + + IMAGE_GEN_DEBUGFS = "1" + IMAGE_FSTYPES_DEBUGFS = "tar.bz2" + + These options cause the + OpenEmbedded build system to generate a special companion filesystem + fragment, which contains the matching source and debug symbols to + your deployable filesystem. The build system does this by looking at + what is in the deployed filesystem, and pulling the corresponding + ``-dbg`` packages. + + The companion debug filesystem is not a complete filesystem, but only + contains the debug fragments. This filesystem must be combined with + the full filesystem for debugging. Subsequent steps in this procedure + show how to combine the partial filesystem with the full filesystem. + +2. *Configure the system to include gdbserver in the target filesystem:* + + Make the following addition in either your ``local.conf`` file or in + an image recipe: + :: + + IMAGE_INSTALL_append = " gdbserver" + + The change makes + sure the ``gdbserver`` package is included. + +3. *Build the environment:* + + Use the following command to construct the image and the companion + Debug Filesystem: + :: + + $ bitbake image + + Build the cross GDB component and + make it available for debugging. Build the SDK that matches the + image. Building the SDK is best for a production build that can be + used later for debugging, especially during long term maintenance: + :: + + $ bitbake -c populate_sdk image + + Alternatively, you can build the minimal toolchain components that + match the target. Doing so creates a smaller than typical SDK and + only contains a minimal set of components with which to build simple + test applications, as well as run the debugger: + :: + + $ bitbake meta-toolchain + + A final method is to build Gdb itself within the build system: + :: + + $ bitbake gdb-cross-<architecture> + + Doing so produces a temporary copy of + ``cross-gdb`` you can use for debugging during development. While + this is the quickest approach, the two previous methods in this step + are better when considering long-term maintenance strategies. + + .. note:: + + If you run ``bitbake gdb-cross``, the OpenEmbedded build system suggests + the actual image (e.g. ``gdb-cross-i586``). The suggestion is usually the + actual name you want to use. + +4. *Set up the* ``debugfs``\ *:* + + Run the following commands to set up the ``debugfs``: + :: + + $ mkdir debugfs + $ cd debugfs + $ tar xvfj build-dir/tmp-glibc/deploy/images/machine/image.rootfs.tar.bz2 + $ tar xvfj build-dir/tmp-glibc/deploy/images/machine/image-dbg.rootfs.tar.bz2 + +5. *Set up GDB:* + + Install the SDK (if you built one) and then source the correct + environment file. Sourcing the environment file puts the SDK in your + ``PATH`` environment variable. + + If you are using the build system, Gdb is located in + `build-dir`\ ``/tmp/sysroots/``\ `host`\ ``/usr/bin/``\ `architecture`\ ``/``\ `architecture`\ ``-gdb`` + +6. *Boot the target:* + + For information on how to run QEMU, see the `QEMU + Documentation <https://wiki.qemu.org/Documentation/GettingStartedDevelopers>`__. + + .. note:: + + Be sure to verify that your host can access the target via TCP. + +7. *Debug a program:* + + Debugging a program involves running gdbserver on the target and then + running Gdb on the host. The example in this step debugs ``gzip``: + + .. code-block:: shell + + root@qemux86:~# gdbserver localhost:1234 /bin/gzip —help + + For + additional gdbserver options, see the `GDB Server + Documentation <https://www.gnu.org/software/gdb/documentation/>`__. + + After running gdbserver on the target, you need to run Gdb on the + host and configure it and connect to the target. Use these commands: + :: + + $ cd directory-holding-the-debugfs-directory + $ arch-gdb + (gdb) set sysroot debugfs + (gdb) set substitute-path /usr/src/debug debugfs/usr/src/debug + (gdb) target remote IP-of-target:1234 + + At this + point, everything should automatically load (i.e. matching binaries, + symbols and headers). + + .. note:: + + The Gdb ``set`` commands in the previous example can be placed into the + users ``~/.gdbinit`` file. Upon starting, Gdb automatically runs whatever + commands are in that file. + +8. *Deploying without a full image rebuild:* + + In many cases, during development you want a quick method to deploy a + new binary to the target and debug it, without waiting for a full + image build. + + One approach to solving this situation is to just build the component + you want to debug. Once you have built the component, copy the + executable directly to both the target and the host ``debugfs``. + + If the binary is processed through the debug splitting in + OpenEmbedded, you should also copy the debug items (i.e. ``.debug`` + contents and corresponding ``/usr/src/debug`` files) from the work + directory. Here is an example: + :: + + $ bitbake bash + $ bitbake -c devshell bash + $ cd .. + $ scp packages-split/bash/bin/bash target:/bin/bash + $ cp -a packages-split/bash-dbg/\* path/debugfs + +Debugging with the GNU Project Debugger (GDB) on the Target +----------------------------------------------------------- + +The previous section addressed using GDB remotely for debugging +purposes, which is the most usual case due to the inherent hardware +limitations on many embedded devices. However, debugging in the target +hardware itself is also possible with more powerful devices. This +section describes what you need to do in order to support using GDB to +debug on the target hardware. + +To support this kind of debugging, you need do the following: + +- Ensure that GDB is on the target. You can do this by adding "gdb" to + :term:`IMAGE_INSTALL`: + :: + + IMAGE_INSTALL_append = " gdb" + + Alternatively, you can add "tools-debug" to :term:`IMAGE_FEATURES`: + :: + + IMAGE_FEATURES_append = " tools-debug" + +- Ensure that debug symbols are present. You can make sure these + symbols are present by installing ``-dbg``: + :: + + IMAGE_INSTALL_append = "packagename-dbg" + + Alternatively, you can do the following to include + all the debug symbols: + :: + + IMAGE_FEATURES_append = " dbg-pkgs" + +.. note:: + + To improve the debug information accuracy, you can reduce the level + of optimization used by the compiler. For example, when adding the + following line to your ``local.conf`` file, you will reduce optimization + from :term:`FULL_OPTIMIZATION` of "-O2" to :term:`DEBUG_OPTIMIZATION` + of "-O -fno-omit-frame-pointer": + :: + + DEBUG_BUILD = "1" + + Consider that this will reduce the application's performance and is + recommended only for debugging purposes. + +Other Debugging Tips +-------------------- + +Here are some other tips that you might find useful: + +- When adding new packages, it is worth watching for undesirable items + making their way into compiler command lines. For example, you do not + want references to local system files like ``/usr/lib/`` or + ``/usr/include/``. + +- If you want to remove the ``psplash`` boot splashscreen, add + ``psplash=false`` to the kernel command line. Doing so prevents + ``psplash`` from loading and thus allows you to see the console. It + is also possible to switch out of the splashscreen by switching the + virtual console (e.g. Fn+Left or Fn+Right on a Zaurus). + +- Removing :term:`TMPDIR` (usually + ``tmp/``, within the + :term:`Build Directory`) can often fix + temporary build issues. Removing ``TMPDIR`` is usually a relatively + cheap operation, because task output will be cached in + :term:`SSTATE_DIR` (usually + ``sstate-cache/``, which is also in the Build Directory). + + .. note:: + + Removing ``TMPDIR`` might be a workaround rather than a fix. + Consequently, trying to determine the underlying cause of an issue before + removing the directory is a good idea. + +- Understanding how a feature is used in practice within existing + recipes can be very helpful. It is recommended that you configure + some method that allows you to quickly search through files. + + Using GNU Grep, you can use the following shell function to + recursively search through common recipe-related files, skipping + binary files, ``.git`` directories, and the Build Directory (assuming + its name starts with "build"): + :: + + g() { + grep -Ir \ + --exclude-dir=.git \ + --exclude-dir='build*' \ + --include='*.bb*' \ + --include='*.inc*' \ + --include='*.conf*' \ + --include='*.py*' \ + "$@" + } + + Following are some usage examples: + :: + + $ g FOO # Search recursively for "FOO" + $ g -i foo # Search recursively for "foo", ignoring case + $ g -w FOO # Search recursively for "FOO" as a word, ignoring e.g. "FOOBAR" + + If figuring + out how some feature works requires a lot of searching, it might + indicate that the documentation should be extended or improved. In + such cases, consider filing a documentation bug using the Yocto + Project implementation of + :yocto_bugs:`Bugzilla <>`. For information on + how to submit a bug against the Yocto Project, see the Yocto Project + Bugzilla :yocto_wiki:`wiki page </Bugzilla_Configuration_and_Bug_Tracking>` + and the "`Submitting a Defect Against the Yocto + Project <#submitting-a-defect-against-the-yocto-project>`__" section. + + .. note:: + + The manuals might not be the right place to document variables + that are purely internal and have a limited scope (e.g. internal + variables used to implement a single ``.bbclass`` file). + +Making Changes to the Yocto Project +=================================== + +Because the Yocto Project is an open-source, community-based project, +you can effect changes to the project. This section presents procedures +that show you how to submit a defect against the project and how to +submit a change. + +Submitting a Defect Against the Yocto Project +--------------------------------------------- + +Use the Yocto Project implementation of +`Bugzilla <https://www.bugzilla.org/about/>`__ to submit a defect (bug) +against the Yocto Project. For additional information on this +implementation of Bugzilla see the ":ref:`Yocto Project +Bugzilla <resources-bugtracker>`" section in the +Yocto Project Reference Manual. For more detail on any of the following +steps, see the Yocto Project +:yocto_wiki:`Bugzilla wiki page </Bugzilla_Configuration_and_Bug_Tracking>`. + +Use the following general steps to submit a bug: + +1. Open the Yocto Project implementation of :yocto_bugs:`Bugzilla <>`. + +2. Click "File a Bug" to enter a new bug. + +3. Choose the appropriate "Classification", "Product", and "Component" + for which the bug was found. Bugs for the Yocto Project fall into + one of several classifications, which in turn break down into + several products and components. For example, for a bug against the + ``meta-intel`` layer, you would choose "Build System, Metadata & + Runtime", "BSPs", and "bsps-meta-intel", respectively. + +4. Choose the "Version" of the Yocto Project for which you found the + bug (e.g. &DISTRO;). + +5. Determine and select the "Severity" of the bug. The severity + indicates how the bug impacted your work. + +6. Choose the "Hardware" that the bug impacts. + +7. Choose the "Architecture" that the bug impacts. + +8. Choose a "Documentation change" item for the bug. Fixing a bug might + or might not affect the Yocto Project documentation. If you are + unsure of the impact to the documentation, select "Don't Know". + +9. Provide a brief "Summary" of the bug. Try to limit your summary to + just a line or two and be sure to capture the essence of the bug. + +10. Provide a detailed "Description" of the bug. You should provide as + much detail as you can about the context, behavior, output, and so + forth that surrounds the bug. You can even attach supporting files + for output from logs by using the "Add an attachment" button. + +11. Click the "Submit Bug" button submit the bug. A new Bugzilla number + is assigned to the bug and the defect is logged in the bug tracking + system. + +Once you file a bug, the bug is processed by the Yocto Project Bug +Triage Team and further details concerning the bug are assigned (e.g. +priority and owner). You are the "Submitter" of the bug and any further +categorization, progress, or comments on the bug result in Bugzilla +sending you an automated email concerning the particular change or +progress to the bug. + +Submitting a Change to the Yocto Project +---------------------------------------- + +Contributions to the Yocto Project and OpenEmbedded are very welcome. +Because the system is extremely configurable and flexible, we recognize +that developers will want to extend, configure or optimize it for their +specific uses. + +The Yocto Project uses a mailing list and a patch-based workflow that is +similar to the Linux kernel but contains important differences. In +general, a mailing list exists through which you can submit patches. You +should send patches to the appropriate mailing list so that they can be +reviewed and merged by the appropriate maintainer. The specific mailing +list you need to use depends on the location of the code you are +changing. Each component (e.g. layer) should have a ``README`` file that +indicates where to send the changes and which process to follow. + +You can send the patch to the mailing list using whichever approach you +feel comfortable with to generate the patch. Once sent, the patch is +usually reviewed by the community at large. If somebody has concerns +with the patch, they will usually voice their concern over the mailing +list. If a patch does not receive any negative reviews, the maintainer +of the affected layer typically takes the patch, tests it, and then +based on successful testing, merges the patch. + +The "poky" repository, which is the Yocto Project's reference build +environment, is a hybrid repository that contains several individual +pieces (e.g. BitBake, Metadata, documentation, and so forth) built using +the combo-layer tool. The upstream location used for submitting changes +varies by component: + +- *Core Metadata:* Send your patch to the + :oe_lists:`openembedded-core </g/openembedded-core>` + mailing list. For example, a change to anything under the ``meta`` or + ``scripts`` directories should be sent to this mailing list. + +- *BitBake:* For changes to BitBake (i.e. anything under the + ``bitbake`` directory), send your patch to the + :oe_lists:`bitbake-devel </g/bitbake-devel>` + mailing list. + +- *"meta-\*" trees:* These trees contain Metadata. Use the + :yocto_lists:`poky </g/poky>` mailing list. + +- *Documentation*: For changes to the Yocto Project documentation, use the + :yocto_lists:`docs </g/docs>` mailing list. + +For changes to other layers hosted in the Yocto Project source +repositories (i.e. ``yoctoproject.org``) and tools use the +:yocto_lists:`Yocto Project </g/yocto/>` general mailing list. + +.. note:: + + Sometimes a layer's documentation specifies to use a particular + mailing list. If so, use that list. + +For additional recipes that do not fit into the core Metadata, you +should determine which layer the recipe should go into and submit the +change in the manner recommended by the documentation (e.g. the +``README`` file) supplied with the layer. If in doubt, please ask on the +Yocto general mailing list or on the openembedded-devel mailing list. + +You can also push a change upstream and request a maintainer to pull the +change into the component's upstream repository. You do this by pushing +to a contribution repository that is upstream. See the +":ref:`overview-manual/overview-manual-development-environment:git workflows and the yocto project`" +section in the Yocto Project Overview and Concepts Manual for additional +concepts on working in the Yocto Project development environment. + +Maintainers commonly use ``-next`` branches to test submissions prior to +merging patches. Thus, you can get an idea of the status of a patch based on +whether the patch has been merged into one of these branches. The commonly +used testing branches for OpenEmbedded-Core are as follows: + +- *openembedded-core "master-next" branch:* This branch is part of the + :oe_git:`openembedded-core </openembedded-core/>` repository and contains + proposed changes to the core metadata. + +- *poky "master-next" branch:* This branch is part of the + :yocto_git:`poky </poky/>` repository and combines proposed + changes to bitbake, the core metadata and the poky distro. + +Similarly, stable branches maintained by the project may have corresponding +``-next`` branches which collect proposed changes. For example, +``&DISTRO_NAME_NO_CAP;-next`` and ``&DISTRO_NAME_NO_CAP_MINUS_ONE;-next`` +branches in both the "openembdedded-core" and "poky" repositories. + +Other layers may have similar testing branches but there is no formal +requirement or standard for these so please check the documentation for the +layers you are contributing to. + +The following sections provide procedures for submitting a change. + +Preparing Changes for Submission +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +1. *Make Your Changes Locally:* Make your changes in your local Git + repository. You should make small, controlled, isolated changes. + Keeping changes small and isolated aids review, makes + merging/rebasing easier and keeps the change history clean should + anyone need to refer to it in future. + +2. *Stage Your Changes:* Stage your changes by using the ``git add`` + command on each file you changed. + +3. *Commit Your Changes:* Commit the change by using the ``git commit`` + command. Make sure your commit information follows standards by + following these accepted conventions: + + - Be sure to include a "Signed-off-by:" line in the same style as + required by the Linux kernel. Adding this line signifies that you, + the submitter, have agreed to the Developer's Certificate of + Origin 1.1 as follows: + + .. code-block:: none + + Developer's Certificate of Origin 1.1 + + By making a contribution to this project, I certify that: + + (a) The contribution was created in whole or in part by me and I + have the right to submit it under the open source license + indicated in the file; or + + (b) The contribution is based upon previous work that, to the best + of my knowledge, is covered under an appropriate open source + license and I have the right under that license to submit that + work with modifications, whether created in whole or in part + by me, under the same open source license (unless I am + permitted to submit under a different license), as indicated + in the file; or + + (c) The contribution was provided directly to me by some other + person who certified (a), (b) or (c) and I have not modified + it. + + (d) I understand and agree that this project and the contribution + are public and that a record of the contribution (including all + personal information I submit with it, including my sign-off) is + maintained indefinitely and may be redistributed consistent with + this project or the open source license(s) involved. + + - Provide a single-line summary of the change and, if more + explanation is needed, provide more detail in the body of the + commit. This summary is typically viewable in the "shortlist" of + changes. Thus, providing something short and descriptive that + gives the reader a summary of the change is useful when viewing a + list of many commits. You should prefix this short description + with the recipe name (if changing a recipe), or else with the + short form path to the file being changed. + + - For the body of the commit message, provide detailed information + that describes what you changed, why you made the change, and the + approach you used. It might also be helpful if you mention how you + tested the change. Provide as much detail as you can in the body + of the commit message. + + .. note:: + + You do not need to provide a more detailed explanation of a + change if the change is minor to the point of the single line + summary providing all the information. + + - If the change addresses a specific bug or issue that is associated + with a bug-tracking ID, include a reference to that ID in your + detailed description. For example, the Yocto Project uses a + specific convention for bug references - any commit that addresses + a specific bug should use the following form for the detailed + description. Be sure to use the actual bug-tracking ID from + Bugzilla for bug-id: + :: + + Fixes [YOCTO #bug-id] + + detailed description of change + +Using Email to Submit a Patch +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Depending on the components changed, you need to submit the email to a +specific mailing list. For some guidance on which mailing list to use, +see the `list <#figuring-out-the-mailing-list-to-use>`__ at the +beginning of this section. For a description of all the available +mailing lists, see the ":ref:`Mailing Lists <resources-mailinglist>`" section in the +Yocto Project Reference Manual. + +Here is the general procedure on how to submit a patch through email +without using the scripts once the steps in +:ref:`dev-manual/common-tasks:preparing changes for submission` have been followed: + +1. *Format the Commit:* Format the commit into an email message. To + format commits, use the ``git format-patch`` command. When you + provide the command, you must include a revision list or a number of + patches as part of the command. For example, either of these two + commands takes your most recent single commit and formats it as an + email message in the current directory: + :: + + $ git format-patch -1 + + or :: + + $ git format-patch HEAD~ + + After the command is run, the current directory contains a numbered + ``.patch`` file for the commit. + + If you provide several commits as part of the command, the + ``git format-patch`` command produces a series of numbered files in + the current directory – one for each commit. If you have more than + one patch, you should also use the ``--cover`` option with the + command, which generates a cover letter as the first "patch" in the + series. You can then edit the cover letter to provide a description + for the series of patches. For information on the + ``git format-patch`` command, see ``GIT_FORMAT_PATCH(1)`` displayed + using the ``man git-format-patch`` command. + + .. note:: + + If you are or will be a frequent contributor to the Yocto Project + or to OpenEmbedded, you might consider requesting a contrib area + and the necessary associated rights. + +2. *Send the patches via email:* Send the patches to the recipients and + relevant mailing lists by using the ``git send-email`` command. + + .. note:: + + In order to use ``git send-email``, you must have the proper Git packages + installed on your host. + For Ubuntu, Debian, and Fedora the package is ``git-email``. + + The ``git send-email`` command sends email by using a local or remote + Mail Transport Agent (MTA) such as ``msmtp``, ``sendmail``, or + through a direct ``smtp`` configuration in your Git ``~/.gitconfig`` + file. If you are submitting patches through email only, it is very + important that you submit them without any whitespace or HTML + formatting that either you or your mailer introduces. The maintainer + that receives your patches needs to be able to save and apply them + directly from your emails. A good way to verify that what you are + sending will be applicable by the maintainer is to do a dry run and + send them to yourself and then save and apply them as the maintainer + would. + + The ``git send-email`` command is the preferred method for sending + your patches using email since there is no risk of compromising + whitespace in the body of the message, which can occur when you use + your own mail client. The command also has several options that let + you specify recipients and perform further editing of the email + message. For information on how to use the ``git send-email`` + command, see ``GIT-SEND-EMAIL(1)`` displayed using the + ``man git-send-email`` command. + +The Yocto Project uses a `Patchwork instance <https://patchwork.openembedded.org/>`__ +to track the status of patches submitted to the various mailing lists and to +support automated patch testing. Each submitted patch is checked for common +mistakes and deviations from the expected patch format and submitters are +notified by patchtest if such mistakes are found. This process helps to +reduce the burden of patch review on maintainers. + +.. note:: + + This system is imperfect and changes can sometimes get lost in the flow. + Asking about the status of a patch or change is reasonable if the change + has been idle for a while with no feedback. + +Using Scripts to Push a Change Upstream and Request a Pull +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +For larger patch series it is preferable to send a pull request which not +only includes the patch but also a pointer to a branch that can be pulled +from. This involves making a local branch for your changes, pushing this +branch to an accessible repository and then using the ``create-pull-request`` +and ``send-pull-request`` scripts from openembedded-core to create and send a +patch series with a link to the branch for review. + +Follow this procedure to push a change to an upstream "contrib" Git +repository once the steps in :ref:`dev-manual/common-tasks:preparing changes for submission` have +been followed: + +.. note:: + + You can find general Git information on how to push a change upstream + in the + `Git Community Book <https://git-scm.com/book/en/v2/Distributed-Git-Distributed-Workflows>`__. + +1. *Push Your Commits to a "Contrib" Upstream:* If you have arranged for + permissions to push to an upstream contrib repository, push the + change to that repository: + :: + + $ git push upstream_remote_repo local_branch_name + + For example, suppose you have permissions to push + into the upstream ``meta-intel-contrib`` repository and you are + working in a local branch named `your_name`\ ``/README``. The following + command pushes your local commits to the ``meta-intel-contrib`` + upstream repository and puts the commit in a branch named + `your_name`\ ``/README``: + :: + + $ git push meta-intel-contrib your_name/README + +2. *Determine Who to Notify:* Determine the maintainer or the mailing + list that you need to notify for the change. + + Before submitting any change, you need to be sure who the maintainer + is or what mailing list that you need to notify. Use either these + methods to find out: + + - *Maintenance File:* Examine the ``maintainers.inc`` file, which is + located in the :term:`Source Directory` at + ``meta/conf/distro/include``, to see who is responsible for code. + + - *Search by File:* Using :ref:`overview-manual/overview-manual-development-environment:git`, you can + enter the following command to bring up a short list of all + commits against a specific file: + :: + + git shortlog -- filename + + Just provide the name of the file for which you are interested. The + information returned is not ordered by history but does include a + list of everyone who has committed grouped by name. From the list, + you can see who is responsible for the bulk of the changes against + the file. + + - *Examine the List of Mailing Lists:* For a list of the Yocto + Project and related mailing lists, see the ":ref:`Mailing + lists <resources-mailinglist>`" section in + the Yocto Project Reference Manual. + +3. *Make a Pull Request:* Notify the maintainer or the mailing list that + you have pushed a change by making a pull request. + + The Yocto Project provides two scripts that conveniently let you + generate and send pull requests to the Yocto Project. These scripts + are ``create-pull-request`` and ``send-pull-request``. You can find + these scripts in the ``scripts`` directory within the + :term:`Source Directory` (e.g. + ``~/poky/scripts``). + + Using these scripts correctly formats the requests without + introducing any whitespace or HTML formatting. The maintainer that + receives your patches either directly or through the mailing list + needs to be able to save and apply them directly from your emails. + Using these scripts is the preferred method for sending patches. + + First, create the pull request. For example, the following command + runs the script, specifies the upstream repository in the contrib + directory into which you pushed the change, and provides a subject + line in the created patch files: + :: + + $ ~/poky/scripts/create-pull-request -u meta-intel-contrib -s "Updated Manual Section Reference in README" + + Running this script forms ``*.patch`` files in a folder named + ``pull-``\ `PID` in the current directory. One of the patch files is a + cover letter. + + Before running the ``send-pull-request`` script, you must edit the + cover letter patch to insert information about your change. After + editing the cover letter, send the pull request. For example, the + following command runs the script and specifies the patch directory + and email address. In this example, the email address is a mailing + list: + :: + + $ ~/poky/scripts/send-pull-request -p ~/meta-intel/pull-10565 -t meta-intel@yoctoproject.org + + You need to follow the prompts as the script is interactive. + + .. note:: + + For help on using these scripts, simply provide the ``-h`` + argument as follows: + :: + + $ poky/scripts/create-pull-request -h + $ poky/scripts/send-pull-request -h + +Responding to Patch Review +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You may get feedback on your submitted patches from other community members +or from the automated patchtest service. If issues are identified in your +patch then it is usually necessary to address these before the patch will be +accepted into the project. In this case you should amend the patch according +to the feedback and submit an updated version to the relevant mailing list, +copying in the reviewers who provided feedback to the previous version of the +patch. + +The patch should be amended using ``git commit --amend`` or perhaps ``git +rebase`` for more expert git users. You should also modify the ``[PATCH]`` +tag in the email subject line when sending the revised patch to mark the new +iteration as ``[PATCH v2]``, ``[PATCH v3]``, etc as appropriate. This can be +done by passing the ``-v`` argument to ``git format-patch`` with a version +number. + +Lastly please ensure that you also test your revised changes. In particular +please don't just edit the patch file written out by ``git format-patch`` and +resend it. + +Submitting Changes to Stable Release Branches +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The process for proposing changes to a Yocto Project stable branch differs +from the steps described above. Changes to a stable branch must address +identified bugs or CVEs and should be made carefully in order to avoid the +risk of introducing new bugs or breaking backwards compatibility. Typically +bug fixes must already be accepted into the master branch before they can be +backported to a stable branch unless the bug in question does not affect the +master branch or the fix on the master branch is unsuitable for backporting. + +The list of stable branches along with the status and maintainer for each +branch can be obtained from the +:yocto_wiki:`Releases wiki page </Releases>`. + +.. note:: + + Changes will not typically be accepted for branches which are marked as + End-Of-Life (EOL). + +With this in mind, the steps to submit a change for a stable branch are as +follows: + +1. *Identify the bug or CVE to be fixed:* This information should be + collected so that it can be included in your submission. + +2. *Check if the fix is already present in the master branch:* This will + result in the most straightforward path into the stable branch for the + fix. + + a. *If the fix is present in the master branch - Submit a backport request + by email:* You should send an email to the relevant stable branch + maintainer and the mailing list with details of the bug or CVE to be + fixed, the commit hash on the master branch that fixes the issue and + the stable branches which you would like this fix to be backported to. + + b. *If the fix is not present in the master branch - Submit the fix to the + master branch first:* This will ensure that the fix passes through the + project's usual patch review and test processes before being accepted. + It will also ensure that bugs are not left unresolved in the master + branch itself. Once the fix is accepted in the master branch a backport + request can be submitted as above. + + c. *If the fix is unsuitable for the master branch - Submit a patch + directly for the stable branch:* This method should be considered as a + last resort. It is typically necessary when the master branch is using + a newer version of the software which includes an upstream fix for the + issue or when the issue has been fixed on the master branch in a way + that introduces backwards incompatible changes. In this case follow the + steps in :ref:`dev-manual/common-tasks:preparing changes for submission` and + :ref:`dev-manual/common-tasks:using email to submit a patch` but modify the subject header of your patch + email to include the name of the stable branch which you are + targetting. This can be done using the ``--subject-prefix`` argument to + ``git format-patch``, for example to submit a patch to the dunfell + branch use + ``git format-patch --subject-prefix='&DISTRO_NAME_NO_CAP_MINUS_ONE;][PATCH' ...``. + +Working With Licenses +===================== + +As mentioned in the ":ref:`overview-manual/overview-manual-development-environment:licensing`" +section in the Yocto Project Overview and Concepts Manual, open source +projects are open to the public and they consequently have different +licensing structures in place. This section describes the mechanism by +which the :term:`OpenEmbedded Build System` +tracks changes to +licensing text and covers how to maintain open source license compliance +during your project's lifecycle. The section also describes how to +enable commercially licensed recipes, which by default are disabled. + +Tracking License Changes +------------------------ + +The license of an upstream project might change in the future. In order +to prevent these changes going unnoticed, the +:term:`LIC_FILES_CHKSUM` +variable tracks changes to the license text. The checksums are validated +at the end of the configure step, and if the checksums do not match, the +build will fail. + +Specifying the ``LIC_FILES_CHKSUM`` Variable +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``LIC_FILES_CHKSUM`` variable contains checksums of the license text +in the source code for the recipe. Following is an example of how to +specify ``LIC_FILES_CHKSUM``: +:: + + LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \ + file://licfile1.txt;beginline=5;endline=29;md5=yyyy \ + file://licfile2.txt;endline=50;md5=zzzz \ + ..." + +.. note:: + + - When using "beginline" and "endline", realize that line numbering + begins with one and not zero. Also, the included lines are + inclusive (i.e. lines five through and including 29 in the + previous example for ``licfile1.txt``). + + - When a license check fails, the selected license text is included + as part of the QA message. Using this output, you can determine + the exact start and finish for the needed license text. + +The build system uses the :term:`S` +variable as the default directory when searching files listed in +``LIC_FILES_CHKSUM``. The previous example employs the default +directory. + +Consider this next example: +:: + + LIC_FILES_CHKSUM = "file://src/ls.c;beginline=5;endline=16;\ + md5=bb14ed3c4cda583abc85401304b5cd4e" + LIC_FILES_CHKSUM = "file://${WORKDIR}/license.html;md5=5c94767cedb5d6987c902ac850ded2c6" + +The first line locates a file in ``${S}/src/ls.c`` and isolates lines +five through 16 as license text. The second line refers to a file in +:term:`WORKDIR`. + +Note that ``LIC_FILES_CHKSUM`` variable is mandatory for all recipes, +unless the ``LICENSE`` variable is set to "CLOSED". + +Explanation of Syntax +~~~~~~~~~~~~~~~~~~~~~ + +As mentioned in the previous section, the ``LIC_FILES_CHKSUM`` variable +lists all the important files that contain the license text for the +source code. It is possible to specify a checksum for an entire file, or +a specific section of a file (specified by beginning and ending line +numbers with the "beginline" and "endline" parameters, respectively). +The latter is useful for source files with a license notice header, +README documents, and so forth. If you do not use the "beginline" +parameter, then it is assumed that the text begins on the first line of +the file. Similarly, if you do not use the "endline" parameter, it is +assumed that the license text ends with the last line of the file. + +The "md5" parameter stores the md5 checksum of the license text. If the +license text changes in any way as compared to this parameter then a +mismatch occurs. This mismatch triggers a build failure and notifies the +developer. Notification allows the developer to review and address the +license text changes. Also note that if a mismatch occurs during the +build, the correct md5 checksum is placed in the build log and can be +easily copied to the recipe. + +There is no limit to how many files you can specify using the +``LIC_FILES_CHKSUM`` variable. Generally, however, every project +requires a few specifications for license tracking. Many projects have a +"COPYING" file that stores the license information for all the source +code files. This practice allows you to just track the "COPYING" file as +long as it is kept up to date. + +.. note:: + + - If you specify an empty or invalid "md5" parameter, + :term:`BitBake` returns an md5 + mis-match error and displays the correct "md5" parameter value + during the build. The correct parameter is also captured in the + build log. + + - If the whole file contains only license text, you do not need to + use the "beginline" and "endline" parameters. + +Enabling Commercially Licensed Recipes +-------------------------------------- + +By default, the OpenEmbedded build system disables components that have +commercial or other special licensing requirements. Such requirements +are defined on a recipe-by-recipe basis through the +:term:`LICENSE_FLAGS` variable +definition in the affected recipe. For instance, the +``poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly`` recipe +contains the following statement: +:: + + LICENSE_FLAGS = "commercial" + +Here is a +slightly more complicated example that contains both an explicit recipe +name and version (after variable expansion): +:: + + LICENSE_FLAGS = "license_${PN}_${PV}" + +In order for a component restricted by a +``LICENSE_FLAGS`` definition to be enabled and included in an image, it +needs to have a matching entry in the global +:term:`LICENSE_FLAGS_WHITELIST` +variable, which is a variable typically defined in your ``local.conf`` +file. For example, to enable the +``poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly`` package, you +could add either the string "commercial_gst-plugins-ugly" or the more +general string "commercial" to ``LICENSE_FLAGS_WHITELIST``. See the +"`License Flag Matching <#license-flag-matching>`__" section for a full +explanation of how ``LICENSE_FLAGS`` matching works. Here is the +example: +:: + + LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly" + +Likewise, to additionally enable the package built from the recipe +containing ``LICENSE_FLAGS = "license_${PN}_${PV}"``, and assuming that +the actual recipe name was ``emgd_1.10.bb``, the following string would +enable that package as well as the original ``gst-plugins-ugly`` +package: +:: + + LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10" + +As a convenience, you do not need to specify the +complete license string in the whitelist for every package. You can use +an abbreviated form, which consists of just the first portion or +portions of the license string before the initial underscore character +or characters. A partial string will match any license that contains the +given string as the first portion of its license. For example, the +following whitelist string will also match both of the packages +previously mentioned as well as any other packages that have licenses +starting with "commercial" or "license". +:: + + LICENSE_FLAGS_WHITELIST = "commercial license" + +License Flag Matching +~~~~~~~~~~~~~~~~~~~~~ + +License flag matching allows you to control what recipes the +OpenEmbedded build system includes in the build. Fundamentally, the +build system attempts to match ``LICENSE_FLAGS`` strings found in +recipes against ``LICENSE_FLAGS_WHITELIST`` strings found in the +whitelist. A match causes the build system to include a recipe in the +build, while failure to find a match causes the build system to exclude +a recipe. + +In general, license flag matching is simple. However, understanding some +concepts will help you correctly and effectively use matching. + +Before a flag defined by a particular recipe is tested against the +contents of the whitelist, the expanded string ``_${PN}`` is appended to +the flag. This expansion makes each ``LICENSE_FLAGS`` value +recipe-specific. After expansion, the string is then matched against the +whitelist. Thus, specifying ``LICENSE_FLAGS = "commercial"`` in recipe +"foo", for example, results in the string ``"commercial_foo"``. And, to +create a match, that string must appear in the whitelist. + +Judicious use of the ``LICENSE_FLAGS`` strings and the contents of the +``LICENSE_FLAGS_WHITELIST`` variable allows you a lot of flexibility for +including or excluding recipes based on licensing. For example, you can +broaden the matching capabilities by using license flags string subsets +in the whitelist. + +.. note:: + + When using a string subset, be sure to use the part of the expanded + string that precedes the appended underscore character (e.g. + ``usethispart_1.3``, ``usethispart_1.4``, and so forth). + +For example, simply specifying the string "commercial" in the whitelist +matches any expanded ``LICENSE_FLAGS`` definition that starts with the +string "commercial" such as "commercial_foo" and "commercial_bar", which +are the strings the build system automatically generates for +hypothetical recipes named "foo" and "bar" assuming those recipes simply +specify the following: +:: + + LICENSE_FLAGS = "commercial" + +Thus, you can choose +to exhaustively enumerate each license flag in the whitelist and allow +only specific recipes into the image, or you can use a string subset +that causes a broader range of matches to allow a range of recipes into +the image. + +This scheme works even if the ``LICENSE_FLAGS`` string already has +``_${PN}`` appended. For example, the build system turns the license +flag "commercial_1.2_foo" into "commercial_1.2_foo_foo" and would match +both the general "commercial" and the specific "commercial_1.2_foo" +strings found in the whitelist, as expected. + +Here are some other scenarios: + +- You can specify a versioned string in the recipe such as + "commercial_foo_1.2" in a "foo" recipe. The build system expands this + string to "commercial_foo_1.2_foo". Combine this license flag with a + whitelist that has the string "commercial" and you match the flag + along with any other flag that starts with the string "commercial". + +- Under the same circumstances, you can use "commercial_foo" in the + whitelist and the build system not only matches "commercial_foo_1.2" + but also matches any license flag with the string "commercial_foo", + regardless of the version. + +- You can be very specific and use both the package and version parts + in the whitelist (e.g. "commercial_foo_1.2") to specifically match a + versioned recipe. + +Other Variables Related to Commercial Licenses +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Other helpful variables related to commercial license handling exist and +are defined in the +``poky/meta/conf/distro/include/default-distrovars.inc`` file: +:: + + COMMERCIAL_AUDIO_PLUGINS ?= "" + COMMERCIAL_VIDEO_PLUGINS ?= "" + +If you +want to enable these components, you can do so by making sure you have +statements similar to the following in your ``local.conf`` configuration +file: +:: + + COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \ + gst-plugins-ugly-mpegaudioparse" + COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \ + gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse" + LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial_qmmp" + + +Of course, you could also create a matching whitelist for those +components using the more general "commercial" in the whitelist, but +that would also enable all the other packages with ``LICENSE_FLAGS`` +containing "commercial", which you may or may not want: +:: + + LICENSE_FLAGS_WHITELIST = "commercial" + +Specifying audio and video plugins as part of the +``COMMERCIAL_AUDIO_PLUGINS`` and ``COMMERCIAL_VIDEO_PLUGINS`` statements +(along with the enabling ``LICENSE_FLAGS_WHITELIST``) includes the +plugins or components into built images, thus adding support for media +formats or components. + +Maintaining Open Source License Compliance During Your Product's Lifecycle +-------------------------------------------------------------------------- + +One of the concerns for a development organization using open source +software is how to maintain compliance with various open source +licensing during the lifecycle of the product. While this section does +not provide legal advice or comprehensively cover all scenarios, it does +present methods that you can use to assist you in meeting the compliance +requirements during a software release. + +With hundreds of different open source licenses that the Yocto Project +tracks, it is difficult to know the requirements of each and every +license. However, the requirements of the major FLOSS licenses can begin +to be covered by assuming that three main areas of concern exist: + +- Source code must be provided. + +- License text for the software must be provided. + +- Compilation scripts and modifications to the source code must be + provided. + +- spdx files can be provided. + +There are other requirements beyond the scope of these three and the +methods described in this section (e.g. the mechanism through which +source code is distributed). + +As different organizations have different methods of complying with open +source licensing, this section is not meant to imply that there is only +one single way to meet your compliance obligations, but rather to +describe one method of achieving compliance. The remainder of this +section describes methods supported to meet the previously mentioned +three requirements. Once you take steps to meet these requirements, and +prior to releasing images, sources, and the build system, you should +audit all artifacts to ensure completeness. + +.. note:: + + The Yocto Project generates a license manifest during image creation + that is located in ``${DEPLOY_DIR}/licenses/``\ `image_name`\ ``-``\ `datestamp` + to assist with any audits. + +Providing the Source Code +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Compliance activities should begin before you generate the final image. +The first thing you should look at is the requirement that tops the list +for most compliance groups - providing the source. The Yocto Project has +a few ways of meeting this requirement. + +One of the easiest ways to meet this requirement is to provide the +entire :term:`DL_DIR` used by the +build. This method, however, has a few issues. The most obvious is the +size of the directory since it includes all sources used in the build +and not just the source used in the released image. It will include +toolchain source, and other artifacts, which you would not generally +release. However, the more serious issue for most companies is +accidental release of proprietary software. The Yocto Project provides +an :ref:`archiver <ref-classes-archiver>` class to +help avoid some of these concerns. + +Before you employ ``DL_DIR`` or the ``archiver`` class, you need to +decide how you choose to provide source. The source ``archiver`` class +can generate tarballs and SRPMs and can create them with various levels +of compliance in mind. + +One way of doing this (but certainly not the only way) is to release +just the source as a tarball. You can do this by adding the following to +the ``local.conf`` file found in the +:term:`Build Directory`: +:: + + INHERIT += "archiver" + ARCHIVER_MODE[src] = "original" + +During the creation of your +image, the source from all recipes that deploy packages to the image is +placed within subdirectories of ``DEPLOY_DIR/sources`` based on the +:term:`LICENSE` for each recipe. +Releasing the entire directory enables you to comply with requirements +concerning providing the unmodified source. It is important to note that +the size of the directory can get large. + +A way to help mitigate the size issue is to only release tarballs for +licenses that require the release of source. Let us assume you are only +concerned with GPL code as identified by running the following script: + +.. code-block:: shell + + # Script to archive a subset of packages matching specific license(s) + # Source and license files are copied into sub folders of package folder + # Must be run from build folder + #!/bin/bash + src_release_dir="source-release" + mkdir -p $src_release_dir + for a in tmp/deploy/sources/*; do + for d in $a/*; do + # Get package name from path + p=`basename $d` + p=${p%-*} + p=${p%-*} + # Only archive GPL packages (update *GPL* regex for your license check) + numfiles=`ls tmp/deploy/licenses/$p/*GPL* 2> /dev/null | wc -l` + if [ $numfiles -gt 1 ]; then + echo Archiving $p + mkdir -p $src_release_dir/$p/source + cp $d/* $src_release_dir/$p/source 2> /dev/null + mkdir -p $src_release_dir/$p/license + cp tmp/deploy/licenses/$p/* $src_release_dir/$p/license 2> /dev/null + fi + done + done + +At this point, you +could create a tarball from the ``gpl_source_release`` directory and +provide that to the end user. This method would be a step toward +achieving compliance with section 3a of GPLv2 and with section 6 of +GPLv3. + +Providing License Text +~~~~~~~~~~~~~~~~~~~~~~ + +One requirement that is often overlooked is inclusion of license text. +This requirement also needs to be dealt with prior to generating the +final image. Some licenses require the license text to accompany the +binary. You can achieve this by adding the following to your +``local.conf`` file: +:: + + COPY_LIC_MANIFEST = "1" + COPY_LIC_DIRS = "1" + LICENSE_CREATE_PACKAGE = "1" + +Adding these statements to the +configuration file ensures that the licenses collected during package +generation are included on your image. + +.. note:: + + Setting all three variables to "1" results in the image having two + copies of the same license file. One copy resides in + ``/usr/share/common-licenses`` and the other resides in + ``/usr/share/license``. + + The reason for this behavior is because + :term:`COPY_LIC_DIRS` and + :term:`COPY_LIC_MANIFEST` + add a copy of the license when the image is built but do not offer a + path for adding licenses for newly installed packages to an image. + :term:`LICENSE_CREATE_PACKAGE` + adds a separate package and an upgrade path for adding licenses to an + image. + +As the source ``archiver`` class has already archived the original +unmodified source that contains the license files, you would have +already met the requirements for inclusion of the license information +with source as defined by the GPL and other open source licenses. + +Providing Compilation Scripts and Source Code Modifications +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +At this point, we have addressed all we need to prior to generating the +image. The next two requirements are addressed during the final +packaging of the release. + +By releasing the version of the OpenEmbedded build system and the layers +used during the build, you will be providing both compilation scripts +and the source code modifications in one step. + +If the deployment team has a :ref:`overview-manual/overview-manual-concepts:bsp layer` +and a distro layer, and those +those layers are used to patch, compile, package, or modify (in any way) +any open source software included in your released images, you might be +required to release those layers under section 3 of GPLv2 or section 1 +of GPLv3. One way of doing that is with a clean checkout of the version +of the Yocto Project and layers used during your build. Here is an +example: + +.. code-block:: shell + + # We built using the dunfell branch of the poky repo + $ git clone -b dunfell git://git.yoctoproject.org/poky + $ cd poky + # We built using the release_branch for our layers + $ git clone -b release_branch git://git.mycompany.com/meta-my-bsp-layer + $ git clone -b release_branch git://git.mycompany.com/meta-my-software-layer + # clean up the .git repos + $ find . -name ".git" -type d -exec rm -rf {} \; + +One +thing a development organization might want to consider for end-user +convenience is to modify ``meta-poky/conf/bblayers.conf.sample`` to +ensure that when the end user utilizes the released build system to +build an image, the development organization's layers are included in +the ``bblayers.conf`` file automatically: +:: + + # POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf + # changes incompatibly + POKY_BBLAYERS_CONF_VERSION = "2" + + BBPATH = "${TOPDIR}" + BBFILES ?= "" + + BBLAYERS ?= " \ + ##OEROOT##/meta \ + ##OEROOT##/meta-poky \ + ##OEROOT##/meta-yocto-bsp \ + ##OEROOT##/meta-mylayer \ + " + +Creating and +providing an archive of the :term:`Metadata` +layers (recipes, configuration files, and so forth) enables you to meet +your requirements to include the scripts to control compilation as well +as any modifications to the original source. + +Providing spdx files +~~~~~~~~~~~~~~~~~~~~~~~~~ + +The spdx module has been integrated to a layer named meta-spdxscanner. +meta-spdxscanner provides several kinds of scanner. If you want to enable +this function, you have to follow the following steps: + +1. Add meta-spdxscanner layer into ``bblayers.conf``. + +2. Refer to the README in meta-spdxscanner to setup the environment (e.g, + setup a fossology server) needed for the scanner. + +3. Meta-spdxscanner provides several methods within the bbclass to create spdx files. + Please choose one that you want to use and enable the spdx task. You have to + add some config options in ``local.conf`` file in your :term:`Build + Directory`. The following is an example showing how to generate spdx files + during bitbake using the fossology-python.bbclass:: + + # Select fossology-python.bbclass. + INHERIT += "fossology-python" + # For fossology-python.bbclass, TOKEN is necessary, so, after setup a + # Fossology server, you have to create a token. + TOKEN = "eyJ0eXAiO..." + # The fossology server is necessary for fossology-python.bbclass. + FOSSOLOGY_SERVER = "http://xx.xx.xx.xx:8081/repo" + # If you want to upload the source code to a special folder: + FOLDER_NAME = "xxxx" //Optional + # If you don't want to put spdx files in tmp/deploy/spdx, you can enable: + SPDX_DEPLOY_DIR = "${DEPLOY_DIR}" //Optional + +For more usage information refer to :yocto_git:`the meta-spdxscanner repository +</meta-spdxscanner/>`. + + +Copying Licenses that Do Not Exist +---------------------------------- + +Some packages, such as the linux-firmware package, have many licenses +that are not in any way common. You can avoid adding a lot of these +types of common license files, which are only applicable to a specific +package, by using the +:term:`NO_GENERIC_LICENSE` +variable. Using this variable also avoids QA errors when you use a +non-common, non-CLOSED license in a recipe. + +The following is an example that uses the ``LICENSE.Abilis.txt`` file as +the license from the fetched source: +:: + + NO_GENERIC_LICENSE[Firmware-Abilis] = "LICENSE.Abilis.txt" + +Using the Error Reporting Tool +============================== + +The error reporting tool allows you to submit errors encountered during +builds to a central database. Outside of the build environment, you can +use a web interface to browse errors, view statistics, and query for +errors. The tool works using a client-server system where the client +portion is integrated with the installed Yocto Project +:term:`Source Directory` (e.g. ``poky``). +The server receives the information collected and saves it in a +database. + +A live instance of the error reporting server exists at +https://errors.yoctoproject.org. This server exists so that when +you want to get help with build failures, you can submit all of the +information on the failure easily and then point to the URL in your bug +report or send an email to the mailing list. + +.. note:: + + If you send error reports to this server, the reports become publicly + visible. + +Enabling and Using the Tool +--------------------------- + +By default, the error reporting tool is disabled. You can enable it by +inheriting the +:ref:`report-error <ref-classes-report-error>` +class by adding the following statement to the end of your +``local.conf`` file in your +:term:`Build Directory`. +:: + + INHERIT += "report-error" + +By default, the error reporting feature stores information in +``${``\ :term:`LOG_DIR`\ ``}/error-report``. +However, you can specify a directory to use by adding the following to +your ``local.conf`` file: +:: + + ERR_REPORT_DIR = "path" + +Enabling error +reporting causes the build process to collect the errors and store them +in a file as previously described. When the build system encounters an +error, it includes a command as part of the console output. You can run +the command to send the error file to the server. For example, the +following command sends the errors to an upstream server: +:: + + $ send-error-report /home/brandusa/project/poky/build/tmp/log/error-report/error_report_201403141617.txt + +In the previous example, the errors are sent to a public database +available at https://errors.yoctoproject.org, which is used by the +entire community. If you specify a particular server, you can send the +errors to a different database. Use the following command for more +information on available options: +:: + + $ send-error-report --help + +When sending the error file, you are prompted to review the data being +sent as well as to provide a name and optional email address. Once you +satisfy these prompts, the command returns a link from the server that +corresponds to your entry in the database. For example, here is a +typical link: https://errors.yoctoproject.org/Errors/Details/9522/ + +Following the link takes you to a web interface where you can browse, +query the errors, and view statistics. + +Disabling the Tool +------------------ + +To disable the error reporting feature, simply remove or comment out the +following statement from the end of your ``local.conf`` file in your +:term:`Build Directory`. +:: + + INHERIT += "report-error" + +Setting Up Your Own Error Reporting Server +------------------------------------------ + +If you want to set up your own error reporting server, you can obtain +the code from the Git repository at :yocto_git:`/error-report-web/`. +Instructions on how to set it up are in the README document. + +Using Wayland and Weston +======================== + +`Wayland <https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)>`__ +is a computer display server protocol that provides a method for +compositing window managers to communicate directly with applications +and video hardware and expects them to communicate with input hardware +using other libraries. Using Wayland with supporting targets can result +in better control over graphics frame rendering than an application +might otherwise achieve. + +The Yocto Project provides the Wayland protocol libraries and the +reference +`Weston <https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)#Weston>`__ +compositor as part of its release. You can find the integrated packages +in the ``meta`` layer of the :term:`Source Directory`. +Specifically, you +can find the recipes that build both Wayland and Weston at +``meta/recipes-graphics/wayland``. + +You can build both the Wayland and Weston packages for use only with +targets that accept the `Mesa 3D and Direct Rendering +Infrastructure <https://en.wikipedia.org/wiki/Mesa_(computer_graphics)>`__, +which is also known as Mesa DRI. This implies that you cannot build and +use the packages if your target uses, for example, the Intel Embedded +Media and Graphics Driver (Intel EMGD) that overrides Mesa DRI. + +.. note:: + + Due to lack of EGL support, Weston 1.0.3 will not run directly on the + emulated QEMU hardware. However, this version of Weston will run + under X emulation without issues. + +This section describes what you need to do to implement Wayland and use +the Weston compositor when building an image for a supporting target. + +Enabling Wayland in an Image +---------------------------- + +To enable Wayland, you need to enable it to be built and enable it to be +included (installed) in the image. + +Building Wayland +~~~~~~~~~~~~~~~~ + +To cause Mesa to build the ``wayland-egl`` platform and Weston to build +Wayland with Kernel Mode Setting +(`KMS <https://wiki.archlinux.org/index.php/Kernel_Mode_Setting>`__) +support, include the "wayland" flag in the +:term:`DISTRO_FEATURES` +statement in your ``local.conf`` file: +:: + + DISTRO_FEATURES_append = " wayland" + +.. note:: + + If X11 has been enabled elsewhere, Weston will build Wayland with X11 + support + +Installing Wayland and Weston +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To install the Wayland feature into an image, you must include the +following +:term:`CORE_IMAGE_EXTRA_INSTALL` +statement in your ``local.conf`` file: +:: + + CORE_IMAGE_EXTRA_INSTALL += "wayland weston" + +Running Weston +-------------- + +To run Weston inside X11, enabling it as described earlier and building +a Sato image is sufficient. If you are running your image under Sato, a +Weston Launcher appears in the "Utility" category. + +Alternatively, you can run Weston through the command-line interpretor +(CLI), which is better suited for development work. To run Weston under +the CLI, you need to do the following after your image is built: + +1. Run these commands to export ``XDG_RUNTIME_DIR``: + :: + + mkdir -p /tmp/$USER-weston + chmod 0700 /tmp/$USER-weston + export XDG_RUNTIME_DIR=/tmp/$USER-weston + +2. Launch Weston in the shell: + :: + + weston |