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diff --git a/documentation/dev-manual/wic.rst b/documentation/dev-manual/wic.rst new file mode 100644 index 0000000000..a3880f3a1c --- /dev/null +++ b/documentation/dev-manual/wic.rst @@ -0,0 +1,731 @@ +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK + +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 +":ref:`dev-manual/wic:generate an image using an existing 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/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 +":ref:`dev-manual/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:`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:`system-requirements-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 wic-tools + +- 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. If multiple candidate files can + be provided by different layers, specify all the possible names through the + :term:`WKS_FILES` variable instead. + +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 + +There is one additional level of help 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 + qemuriscv Create qcow2 image for RISC-V QEMU machines + mkefidisk Create an EFI disk image + qemuloongarch Create qcow2 image for LoongArch QEMU machines + directdisk-multi-rootfs Create multi rootfs image using rootfs plugin + directdisk Create a 'pcbios' direct disk image + efi-bootdisk + mkhybridiso Create a hybrid ISO image + directdisk-gpt Create a 'pcbios' direct disk image + systemd-bootdisk Create an EFI disk image with systemd-boot + sdimage-bootpart Create SD card image with a boot partition + qemux86-directdisk Create a qemu machine 'pcbios' direct disk image + 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 +:term:`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 +:term:`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 :term:`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/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 + qemuriscv Create qcow2 image for RISC-V QEMU machines + mkefidisk Create an EFI disk image + qemuloongarch Create qcow2 image for LoongArch QEMU machines + directdisk-multi-rootfs Create multi rootfs image using rootfs plugin + directdisk Create a 'pcbios' direct disk image + efi-bootdisk + mkhybridiso Create a hybrid ISO image + directdisk-gpt Create a 'pcbios' direct disk image + systemd-bootdisk Create an EFI disk image with systemd-boot + sdimage-bootpart Create SD card image with a boot partition + qemux86-directdisk Create a qemu machine 'pcbios' direct disk image + 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 +":ref:`dev-manual/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/yocto/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs + BOOTIMG_DIR: /home/stephano/yocto/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share + KERNEL_DIR: /home/stephano/yocto/build/tmp-glibc/deploy/images/qemux86 + NATIVE_SYSROOT: /home/stephano/yocto/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/yocto/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 +:term:`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-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/bmaptool: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/yocto/poky/scripts/lib/wic/canned-wks/directdisk-gpt.wks \ + /home/stephano/yocto/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/yocto/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs + BOOTIMG_DIR: /home/stephano/yocto/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share + KERNEL_DIR: /home/stephano/yocto/build/tmp-glibc/deploy/images/qemux86 + NATIVE_SYSROOT: /home/stephano/yocto/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/yocto/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 test.wks -o /home/stephano/testwic \ + --rootfs-dir /home/stephano/yocto/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/rootfs \ + --bootimg-dir /home/stephano/yocto/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share \ + --kernel-dir /home/stephano/yocto/build/tmp/deploy/images/qemux86 \ + --native-sysroot /home/stephano/yocto/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/yocto/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs + BOOTIMG_DIR: /home/stephano/yocto/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share + KERNEL_DIR: /home/stephano/yocto/build/tmp-glibc/deploy/images/qemux86 + NATIVE_SYSROOT: /home/stephano/yocto/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: + 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: + +#. *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. + +#. *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 + + +#. *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 + +#. *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:: + + $ wic 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/bmaptool: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``. + |