367 lines
17 KiB
XML
367 lines
17 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<chapter id='usingpoky'>
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<title>Using the Yocto Project</title>
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<para>
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This chapter describes common usage for the Yocto Project.
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The information is introductory in nature as other manuals in the Yocto Project
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provide more details on how to use the Yocto Project.
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</para>
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<section id='usingpoky-build'>
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<title>Running a Build</title>
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<para>
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You can find general information on how to build an image using the
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Yocto Project in the
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<ulink url='http://www.yoctoproject.org/docs/1.1.1/yocto-project-qs/yocto-project-qs.html#building-image'>
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Building an Image</ulink> section of the
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<ulink url='http://www.yoctoproject.org/docs/1.1.1/yocto-project-qs/yocto-project-qs.html'>
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Yocto Project Quick Start</ulink>.
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This section provides a summary of the build process and provides information
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for less obvious aspects of the build process.
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</para>
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<section id='build-overview'>
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<title>Build Overview</title>
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<para>
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The first thing you need to do is set up the Yocto Project build environment by sourcing
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the environment setup script as follows:
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<literallayout class='monospaced'>
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$ source oe-init-build-env [build_dir]
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</literallayout>
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</para>
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<para>
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The <filename>build_dir</filename> is optional and specifies the directory Yocto Project
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uses for the build.
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If you do not specify a build directory it defaults to <filename>build</filename>
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in your current working directory.
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A common practice is to use a different build directory for different targets.
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For example, <filename>~/build/x86</filename> for a <filename>qemux86</filename>
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target, and <filename>~/build/arm</filename> for a <filename>qemuarm</filename> target.
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See <link linkend="structure-core-script">oe-init-build-env</link>
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for more information on this script.
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</para>
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<para>
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Once the Yocto Project build environment is set up, you can build a target using:
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<literallayout class='monospaced'>
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$ bitbake <target>
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</literallayout>
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</para>
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<para>
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The <filename>target</filename> is the name of the recipe you want to build.
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Common targets are the images in <filename>meta/recipes-core/images</filename>,
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<filename>/meta/recipes-sato/images</filename>, etc. all found in the Yocto Project
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files.
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Or, the target can be the name of a recipe for a specific piece of software such as
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<application>busybox</application>.
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For more details about the images Yocto Project supports, see the
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<link linkend="ref-images">'Reference: Images'</link> appendix.
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</para>
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<note>
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Building an image without GNU Public License Version 3 (GPLv3) components is
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only supported for minimal and base images.
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See <link linkend='ref-images'>'Reference: Images'</link> for more information.
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</note>
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</section>
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<section id='building-an-image-using-gpl-components'>
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<title>Building an Image Using GPL Components</title>
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<para>
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When building an image using GPL components, you need to maintain your original
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settings and not switch back and forth applying different versions of the GNU
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Public License.
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If you rebuild using different versions of GPL, dependency errors might occur
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due to some components not being rebuilt.
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</para>
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</section>
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</section>
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<section id='usingpoky-install'>
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<title>Installing and Using the Result</title>
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<para>
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Once an image has been built, it often needs to be installed.
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The images and kernels built by the Yocto Project are placed in the build directory in
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<filename class="directory">tmp/deploy/images</filename>.
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For information on how to run pre-built images such as <filename>qemux86</filename>
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and <filename>qemuarm</filename>, see the
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<ulink url='http://www.yoctoproject.org/docs/1.1.1/yocto-project-qs/yocto-project-qs.html#using-pre-built'>
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Using Pre-Built Binaries and QEMU</ulink> section in the
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<ulink url='http://www.yoctoproject.org/docs/1.1.1/yocto-project-qs/yocto-project-qs.html'>
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Yocto Project Quick Start</ulink>.
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For information about how to install these images, see the documentation for your
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particular board/machine.
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</para>
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</section>
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<section id='usingpoky-debugging'>
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<title>Debugging Build Failures</title>
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<para>
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The exact method for debugging Yocto Project build failures depends on the nature of the
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problem and on the system's area from which the bug originates.
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Standard debugging practices such as comparison against the last
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known working version with examination of the changes and the re-application of steps
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to identify the one causing the problem are
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valid for Yocto Project just as they are for any other system.
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Even though it is impossible to detail every possible potential failure,
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this section provides some general tips to aid in debugging.
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</para>
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<section id='usingpoky-debugging-taskfailures'>
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<title>Task Failures</title>
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<para>The log file for shell tasks is available in
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<filename>${WORKDIR}/temp/log.do_taskname.pid</filename>.
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For example, the <filename>compile</filename> task for the QEMU minimal image for the x86
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machine (<filename>qemux86</filename>) might be
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<filename>tmp/work/qemux86-poky-linux/core-image-minimal-1.0-r0/temp/log.do_compile.20830</filename>.
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To see what BitBake runs to generate that log, look at the corresponding
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<filename>run.do_taskname.pid</filename> file located in the same directory.
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</para>
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<para>
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Presently, the output from Python tasks is sent directly to the console.
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</para>
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</section>
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<section id='usingpoky-debugging-taskrunning'>
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<title>Running Specific Tasks</title>
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<para>
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Any given package consists of a set of tasks.
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The standard BitBake behavior in most cases is: <filename>fetch</filename>,
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<filename>unpack</filename>,
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<filename>patch</filename>, <filename>configure</filename>,
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<filename>compile</filename>, <filename>install</filename>, <filename>package</filename>,
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<filename>package_write</filename>, and <filename>build</filename>.
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The default task is <filename>build</filename> and any tasks on which it depends
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build first.
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Some tasks exist, such as <filename>devshell</filename>, that are not part of the
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default build chain.
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If you wish to run a task that is not part of the default build chain, you can use the
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<filename>-c</filename> option in BitBake as follows:
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<literallayout class='monospaced'>
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$ bitbake matchbox-desktop -c devshell
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</literallayout>
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</para>
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<para>
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If you wish to rerun a task, use the <filename>-f</filename> force option.
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For example, the following sequence forces recompilation after changing files in the
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working directory.
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<literallayout class='monospaced'>
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$ bitbake matchbox-desktop
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.
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.
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[make some changes to the source code in the working directory]
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.
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.
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$ bitbake matchbox-desktop -c compile -f
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$ bitbake matchbox-desktop
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</literallayout>
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</para>
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<para>
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This sequence first builds <filename>matchbox-desktop</filename> and then recompiles it.
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The last command reruns all tasks (basically the packaging tasks) after the compile.
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BitBake recognizes that the <filename>compile</filename> task was rerun and therefore
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understands that the other tasks also need to be run again.
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</para>
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<para>
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You can view a list of tasks in a given package by running the
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<filename>listtasks</filename> task as follows:
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<literallayout class='monospaced'>
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$ bitbake matchbox-desktop -c
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</literallayout>
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The results are in the file <filename>${WORKDIR}/temp/log.do_listtasks</filename>.
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</para>
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</section>
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<section id='usingpoky-debugging-dependencies'>
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<title>Dependency Graphs</title>
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<para>
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Sometimes it can be hard to see why BitBake wants to build some other packages before a given
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package you have specified.
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The <filename>bitbake -g targetname</filename> command creates the
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<filename>depends.dot</filename> and <filename>task-depends.dot</filename> files
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in the current directory.
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These files show the package and task dependencies and are useful for debugging problems.
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You can use the <filename>bitbake -g -u depexp targetname</filename> command to
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display the results in a more human-readable form.
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</para>
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</section>
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<section id='usingpoky-debugging-bitbake'>
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<title>General BitBake Problems</title>
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<para>
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You can see debug output from BitBake by using the <filename>-D</filename> option.
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The debug output gives more information about what BitBake
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is doing and the reason behind it.
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Each <filename>-D</filename> option you use increases the logging level.
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The most common usage is <filename>-DDD</filename>.
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</para>
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<para>
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The output from <filename>bitbake -DDD -v targetname</filename> can reveal why
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BitBake chose a certain version of a package or why BitBake
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picked a certain provider.
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This command could also help you in a situation where you think BitBake did something
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unexpected.
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</para>
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</section>
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<section id='usingpoky-debugging-buildfile'>
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<title>Building with No Dependencies</title>
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<para>
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If you really want to build a specific <filename>.bb</filename> file, you can use
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the command form <filename>bitbake -b <somepath/somefile.bb></filename>.
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This command form does not check for dependencies so you should use it
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only when you know its dependencies already exist.
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You can also specify fragments of the filename.
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In this case, BitBake checks for a unique match.
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</para>
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</section>
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<section id='usingpoky-debugging-variables'>
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<title>Variables</title>
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<para>
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The <filename>-e</filename> option dumps the resulting environment for
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either the configuration (no package specified) or for a
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specific package when specified; or <filename>-b recipename</filename>
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to show the environment from parsing a single recipe file only.
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</para>
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</section>
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<section id='recipe-logging-mechanisms'>
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<title>Recipe Logging Mechanisms</title>
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<para>
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Best practices exist while writing recipes that both log build progress and
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act on build conditions such as warnings and errors.
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Both Python and Bash language bindings exist for the logging mechanism:
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<itemizedlist>
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<listitem><para><emphasis>Python:</emphasis> For Python functions, BitBake
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supports several loglevels: <filename>bb.fatal</filename>,
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<filename>bb.error</filename>, <filename>bb.warn</filename>,
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<filename>bb.note</filename>, <filename>bb.plain</filename>,
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and <filename>bb.debug</filename>.</para></listitem>
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<listitem><para><emphasis>Bash:</emphasis> For Bash functions, the same set
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of loglevels exist and are accessed with a similar syntax:
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<filename>bbfatal</filename>, <filename>bberror</filename>,
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<filename>bbwarn</filename>, <filename>bbnote</filename>,
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<filename>bbplain</filename>, and <filename>bbdebug</filename>.</para></listitem>
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</itemizedlist>
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</para>
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<para>
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For guidance on how logging is handled
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in both Python and Bash recipes, see the
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<filename>logging.bbclass</filename> file in the
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<filename>meta/classes</filename> directory of the Yocto Project files.
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</para>
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<section id='logging-with-python'>
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<title>Logging With Python</title>
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<para>
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When creating recipes using Python and inserting code that handles build logs
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keep in mind the goal is to have informative logs while keeping the console as
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"silent" as possible.
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Also, if you want status messages in the log use the "debug" loglevel.
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</para>
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<para>
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Following is an example written in Python.
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The code handles logging for a function that determines the number of tasks
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needed to be run:
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<literallayout class='monospaced'>
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python do_listtasks() {
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bb.debug(2, "Starting to figure out the task list")
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if noteworthy_condition:
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bb.note("There are 47 tasks to run")
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bb.debug(2, "Got to point xyz")
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if warning_trigger:
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bb.warn("Detected warning_trigger, this might be a problem later.")
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if recoverable_error:
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bb.error("Hit recoverable_error, you really need to fix this!")
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if fatal_error:
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bb.fatal("fatal_error detected, unable to print the task list")
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bb.plain("The tasks present are abc")
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bb.debug(2, "Finished figureing out the tasklist")
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}
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</literallayout>
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</para>
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</section>
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<section id='logging-with-bash'>
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<title>Logging With Bash</title>
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<para>
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When creating recipes using Bash and inserting code that handles build
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logs you have the same goals - informative with minimal console output.
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The syntax you use for recipes written in Bash is similar to that of
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recipes written in Python described in the previous section.
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</para>
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<para>
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Following is an example written in Bash.
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The code logs the progress of the <filename>do_my_function</filename> function.
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<literallayout class='monospaced'>
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do_my_function() {
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bbdebug 2 "Running do_my_function"
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if [ exceptional_condition ]; then
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bbnote "Hit exceptional_condition"
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fi
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bbdebug 2 "Got to point xyz"
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if [ warning_trigger ]; then
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bbwarn "Detected warning_trigger, this might cause a problem later."
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fi
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if [ recoverable_error ]; then
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bberror "Hit recoverable_error, correcting"
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fi
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if [ fatal_error ]; then
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bbfatal "fatal_error detected"
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fi
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bbdebug 2 "Completed do_my_function"
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}
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</literallayout>
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</para>
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</section>
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</section>
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<section id='usingpoky-debugging-others'>
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<title>Other Tips</title>
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<para>
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Here are some other tips that you might find useful:
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<itemizedlist>
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<listitem><para>When adding new packages, it is worth watching for
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undesirable items making their way into compiler command lines.
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For example, you do not want references to local system files like
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<filename>/usr/lib/</filename> or <filename>/usr/include/</filename>.
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</para></listitem>
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<listitem><para>If you want to remove the psplash boot splashscreen,
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add <filename>psplash=false</filename> to the kernel command line.
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Doing so prevents psplash from loading and thus allows you to see the console.
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It is also possible to switch out of the splashscreen by
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switching the virtual console (e.g. Fn+Left or Fn+Right on a Zaurus).
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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</section>
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</chapter>
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<!--
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vim: expandtab tw=80 ts=4
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-->
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