%poky; ] > This chapter describes common usage for the Yocto Project. The information is introductory in nature as other manuals in the Yocto Project documentation set provide more details on how to use the Yocto Project.

This section provides a summary of the build process and provides information for less obvious aspects of the build process. For general information on how to build an image using the OpenEmbedded build system, see the "Building an Image" section of the Yocto Project Quick Start.

The first thing you need to do is set up the OpenEmbedded build environment by sourcing the environment setup script as follows: $ source &OE_INIT_FILE; [build_dir] The build_dir is optional and specifies the directory the OpenEmbedded build system uses for the build - the Build Directory. If you do not specify a Build Directory it defaults to build in your current working directory. 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. See &OE_INIT_FILE; for more information on this script. Once the build environment is set up, you can build a target using: $ bitbake <target> 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, etc. all found in the 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 "Images" chapter. Building an image without GNU General Public License Version 3 (GPLv3) components is only supported for minimal and base images. See the "Images" chapter for more information.

When building an image using GPL components, you need to maintain your original settings and not switch back and forth applying different versions of the GNU General Public License. If you rebuild using different versions of GPL, dependency errors might occur due to some components not being rebuilt.

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 "Using Pre-Built Binaries and QEMU" section in the Yocto Project Quick Start. For information about how to install these images, see the documentation for your particular board/machine.

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.

The log file for shell tasks is available in ${WORKDIR}/temp/log.do_taskname.pid. For example, the compile task for the QEMU minimal image for the x86 machine (qemux86) might be tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile.20830. To see what BitBake runs to generate that log, look at the corresponding run.do_taskname.pid file located in the same directory. Presently, the output from Python tasks is sent directly to the console.

Any given package consists of a set of tasks. The standard BitBake behavior in most cases is: fetch, unpack, patch, configure, compile, install, package, package_write, and build. The default task is build and any tasks on which it depends build first. Some tasks exist, such as devshell, that 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 as follows: $ bitbake matchbox-desktop -c devshell If you wish to rerun a task, use the -f force option. For example, the following sequence forces recompilation after changing files in the working directory. $ bitbake matchbox-desktop . . [make some changes to the source code in the working directory] . . $ bitbake matchbox-desktop -c compile -f $ bitbake matchbox-desktop This sequence first builds matchbox-desktop and then recompiles it. The last command reruns all tasks (basically the packaging tasks) after the compile. BitBake recognizes that the compile task was rerun and therefore understands that the other tasks also need to be run again. You can view a list of tasks in a given package by running the listtasks task as follows: $ bitbake matchbox-desktop -c listtasks The results are in the file ${WORKDIR}/temp/log.do_listtasks.

Sometimes it can be hard to see why BitBake wants to build some other packages before a given package you have specified. The bitbake -g targetname command creates the depends.dot, package-depends.dot, and task-depends.dot files in the current directory. These files show the package and task dependencies and are useful for debugging problems. You can use the bitbake -g -u depexp targetname command to display the results in a more human-readable form.

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.

Sometimes issues on the host development system can cause your build to fail. Following are known, host-specific problems. Be sure to always consult the Release Notes for a look at all release-related issues. eglibc-initial fails to build: If your development host system has the unpatched GNU Make 3.82, the do_install task fails for eglibc-initial during the build. Typically, every distrobution that ships GNU Make 3.82 as the default already has the patched version. However, some distributions, such as Debian, have GNU Make 3.82 as an option, which is unpatched. You will see this error on these types of distributions. Switch to GNU Make 3.81 or patch your make to solve the problem.

If you really want to build a specific .bb file, you can use the command form bitbake -b <somepath/somefile.bb>. This command form does not check for dependencies so you should use it only when you know its dependencies already exist. You can also specify fragments of the filename. In this case, BitBake checks for a unique match.

The -e option dumps the resulting environment for either the configuration (no package specified) or for a specific package when specified; or -b recipename to show the environment from parsing a single recipe file only.

Best practices exist while writing recipes that both log build progress and act on build conditions such as warnings and errors. Both Python and Bash language bindings exist for the logging mechanism: Python: For Python functions, BitBake supports several loglevels: bb.fatal, bb.error, bb.warn, bb.note, bb.plain, and bb.debug. Bash: For Bash functions, the same set of loglevels exist and are accessed with a similar syntax: bbfatal, bberror, bbwarn, bbnote, bbplain, and bbdebug. For guidance on how logging is handled in both Python and Bash recipes, see the logging.bbclass file in the meta/classes folder of the Source Directory.

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: 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") }

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" }

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).

A build's quality can be influenced by many things. 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, then 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 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: How you can enable and disable build history How to understand what the build history contains How to limit the information used for build history How to examine the build history from both a command-line and web interface

Build history is disabled by default. To enable it, add the following statements to the end of your conf/local.conf file found in the Build Directory: INHERIT += "buildhistory" BUILDHISTORY_COMMIT = "1" Enabling build history as previously described causes the build process to collect build output information and commit it to a local Git repository. 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. However, you should realize that enabling and disabling build history in this manner can change the do_package task checksums, which if you are using the OEBasicHash signature generator (the default for many current distro configurations including DISTRO = "poky" and DISTRO = "") will result in the packaging tasks being re-run during the subsequent build. To disable the build history functionality without causing the packaging tasks to be re-run, add just this statement to your conf/local.conf file: BUILDHISTORY_FEATURES = ""

Build history information is kept in $TMPDIR/buildhistory in the Build Directory. The following is an example abbreviated listing:

The history for each package contains a text file that has name-value pairs with information about the package. For example, buildhistory/packages/core2-poky-linux/busybox/busybox/latest contains the following: PV = 1.19.3 PR = r3 RDEPENDS = update-rc.d eglibc (>= 2.13) RRECOMMENDS = busybox-syslog busybox-udhcpc PKGSIZE = 564701 FILES = /usr/bin/* /usr/sbin/* /usr/libexec/* /usr/lib/lib*.so.* \ /etc /com /var /bin/* /sbin/* /lib/*.so.* /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 = /etc/busybox.links /etc/init.d/hwclock.sh /bin/busybox /bin/sh Most of these name-value pairs corresponds 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. There is also a file corresponding to the recipe from which the package came (e.g. buildhistory/packages/core2-poky-linux/busybox/latest): PV = 1.19.3 PR = r3 DEPENDS = virtual/i586-poky-linux-gcc virtual/i586-poky-linux-compilerlibs \ virtual/libc update-rc.d-native PACKAGES = busybox-httpd busybox-udhcpd busybox-udhcpc busybox-syslog \ busybox-mdev busybox-dbg busybox busybox-doc busybox-dev \ busybox-staticdev busybox-locale

The files produced for each image are as follows: build-id: Human-readable information about the build configuration and metadata source revisions. *.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 fuill package filenames. 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: DISTRO = poky DISTRO_VERSION = 1.1+snapshot-20120207 USER_CLASSES = image-mklibs image-prelink IMAGE_CLASSES = image_types IMAGE_FEATURES = debug-tweaks x11-base apps-x11-core \ package-management ssh-server-dropbear package-management IMAGE_LINGUAS = en-us en-gb IMAGE_INSTALL = task-core-boot task-base-extended BAD_RECOMMENDATIONS = ROOTFS_POSTPROCESS_COMMAND = buildhistory_get_image_installed ; rootfs_update_timestamp ; IMAGE_POSTPROCESS_COMMAND = buildhistory_get_imageinfo ; IMAGESIZE = 171816 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.

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 history or any package information, you can enable writing only image information without any history by adding the following to your conf/local.conf file found in the Build Directory: INHERIT += "buildhistory" BUILDHISTORY_COMMIT = "0" BUILDHISTORY_FEATURES = "image"

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 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/eglibc/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/eglibc/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" To see changes to the build history using a web interface, follow the instruction in the README file here. . Here is a sample screenshot of the interface: