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+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<chapter id="user-manual-execution">
+ <title>Execution</title>
+
+ <para>
+ Tasks can either be a shell task or a Python task.
+ For shell tasks, BitBake writes a shell script to
+ <filename>${WORKDIR}/temp/run.do_taskname.pid</filename>
+ and then executes the script.
+ The generated shell script contains all the exported variables,
+ and the shell functions with all variables expanded.
+ Output from the shell script goes to the file
+ <filename>${WORKDIR}/temp/log.do_taskname.pid</filename>.
+ Looking at the expanded shell functions in the run file and
+ the output in the log files is a useful debugging technique.
+ </para>
+
+ <para>
+ For Python tasks, BitBake executes the task internally and logs
+ information to the controlling terminal.
+ Future versions of BitBake will write the functions to files
+ similar to the way shell tasks are handled.
+ Logging will be handled in a way similar to shell tasks as well.
+ </para>
+
+ <para>
+ Once all the tasks have been completed BitBake exits.
+ </para>
+
+ <section id='parsing-and-execution'>
+ <title>Parsing and Execution</title>
+
+ <section id='parsing-overview'>
+ <title>Parsing Overview</title>
+
+ <para>
+ BitBake parses configuration files, classes, recipes, and append
+ files.
+ </para>
+
+ <para>
+ The first thing BitBake does is look for the
+ <filename>bitbake.conf</filename> file.
+ This file resides in the <filename>conf</filename>
+ directory, which must be listed in
+ <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
+ </para>
+
+ <para>
+ The <filename>bitbake.conf</filename> file lists other configuration
+ files to include from the <filename>conf</filename> directory below the
+ directories listed in <filename>BBPATH</filename>.
+ In general, the most important of these
+ configuration files from a user's perspective
+ is <filename>local.conf</filename>, which contains the user's
+ customized settings for the build environment.
+ </para>
+
+ <para>
+ Other notable configuration files are the distribution configuration
+ file and the machine configuration file.
+ These configuration files are normally identified by
+ variables unique to the build systems using BitBake.
+ For example, the Yocto Project uses the
+ <filename>DISTRO</filename> and <filename>MACHINE</filename>
+ variables, respectively.
+ </para>
+
+ <para>
+ After parsing of the configuration files, some standard classes are
+ included.
+ The <filename>base.bbclass</filename> file
+ is always included.
+ Other classes that are specified in the configuration using the
+ <link linkend='var-INHERIT'><filename>INHERIT</filename></link>
+ variable are also included.
+ BitBake searches for class files in a "classes" subdirectory under
+ the paths in <filename>BBPATH</filename> in the same way as
+ configuration files.
+ </para>
+
+ <para>
+ After classes are included, the variable
+ <filename>BBFILES</filename> is set, usually in
+ <filename>local.conf</filename>, and defines the list of
+ places to search for recipe and append files.
+ Adding extra content to <filename>BBFILES</filename> is best
+ achieved through the use of BitBake layers.
+ </para>
+
+ <para>
+ BitBake parses each recipe and append file located with
+ <filename>BBFILES</filename> and stores the values of various
+ variables into the datastore.
+ In summary, for each recipe and append file pairing, the configuration
+ plus the base class of variables are set, followed by the data in the
+ recipe file itself, followed by any inherit commands
+ that the recipe file might contain.
+ </para>
+
+ <para>
+ Because parsing recipe and append files is a time consuming
+ process, a cache, referred to as the "setscene"
+ is kept to speed up subsequent parsing.
+ The setscene is invalid if the timestamps of a recipe changes,
+ any of the include files change, configuration files change,
+ or class files on which the recipe file depends change.
+ </para>
+ </section>
+
+ <section id='parsing-configuration-files'>
+ <title>Configuration files</title>
+
+ <para>
+ Prior to parsing configuration files, Bitbake looks
+ at certain variables, including:
+ <itemizedlist>
+ <listitem><para><link linkend='var-BB_ENV_WHITELIST'><filename>BB_ENV_WHITELIST</filename></link></para></listitem>
+ <listitem><para><link linkend='var-BB_PRESERVE_ENV'><filename>BB_PRESERVE_ENV</filename></link></para></listitem>
+ <listitem><para><link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link></para></listitem>
+ <listitem><para><link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link></para></listitem>
+ <listitem><para><link linkend='var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></link></para></listitem>
+ <listitem><para><link linkend='var-PREFERRED_PROVIDERS'><filename>PREFERRED_PROVIDERS</filename></link></para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ The first kind of metadata in BitBake is configuration metadata.
+ This metadata is global, and therefore affects all packages and
+ tasks that are executed.
+ </para>
+
+ <para>
+ BitBake will first search the current working directory for an
+ optional <filename>conf/bblayers.conf</filename> configuration file.
+ This file is expected to contain a
+ <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link>
+ variable that is a space delimited list of 'layer' directories.
+ For each directory in this list, a <filename>conf/layer.conf</filename>
+ file will be searched for and parsed with the
+ <link linkend='var-LAYERDIR'><filename>LAYERDIR</filename></link>
+ variable being set to the directory where the layer was found.
+ The idea is these files will setup
+ <link linkend='var-BBPATH'><filename>BBPATH</filename></link>
+ and other variables correctly for a given build directory automatically
+ for the user.
+ </para>
+
+ <para>
+ BitBake will then expect to find <filename>conf/bitbake.conf</filename>
+ file somewhere in the user specified <filename>BBPATH</filename>.
+ That configuration file generally has include directives to pull
+ in any other metadata (generally files specific to architecture,
+ machine, local and so on).
+ </para>
+
+ <para>
+ Only variable definitions and include directives are allowed
+ in <filename>.conf</filename> files.
+ The following variables include:
+ <itemizedlist>
+ <listitem><para>
+ <link linkend='var-BITBAKE_UI'><filename>BITBAKE_UI</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BBDEBUG'><filename>BBDEBUG</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-MULTI_PROVIDER_WHITELIST'><filename>MULTI_PROVIDER_WHITELIST</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <filename>BBPKGS</filename>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BB_DEFAULT_TASK'><filename>BB_DEFAULT_TASK</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BB_VERBOSE_LOGS'><filename>BB_VERBOSE_LOGS</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BB_NICE_LEVEL'><filename>BB_NICE_LEVEL</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BBFILE_COLLECTIONS'><filename>BBFILE_COLLECTIONS</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BB_DANGLINGAPPENDS_WARNONLY'><filename>BB_DANGLINGAPPENDS_WARNONLY</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BBINCLUDED'><filename>BBINCLUDED</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BBFILE_PRIORITY'><filename>BBFILE_PRIORITY</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BUILDNAME'><filename>BUILDNAME</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BBMASK'><filename>BBMASK</filename></link>
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <section id='layers'>
+ <title>Layers</title>
+
+ <para>
+ Layers allow you to isolate different types of
+ customizations from each other.
+ While you might find it tempting to keep everything in one layer
+ when working on a single project, the more modular you organize
+ your metadata, the easier it is to cope with future changes.
+ </para>
+
+ <para>
+ To illustrate how you can use layers to keep things modular,
+ consider machine customizations.
+ These types of customizations typically reside in a special layer,
+ rather than a general layer, called a Board Specific Package (BSP) Layer.
+ Furthermore, the machine customizations should be isolated from
+ recipes and metadata that support a new GUI environment, for
+ example.
+ This situation gives you a couple of layers: one for the machine
+ configurations and one for the GUI environment.
+ It is important to understand, however, that the BSP layer can still
+ make machine-specific additions to recipes within
+ the GUI environment layer without polluting the GUI layer itself
+ with those machine-specific changes.
+ You can accomplish this through a recipe that is a BitBake append
+ (<filename>.bbappend</filename>) file.
+ </para>
+
+ <para>
+ There are certain variables specific to layers:
+ <itemizedlist>
+ <listitem><para>
+ <link linkend='var-LAYERDEPENDS'><filename>LAYERDEPENDS</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-LAYERVERSION'><filename>LAYERVERSION</filename></link>
+ </para></listitem>
+ </itemizedlist>
+ </para>
+ </section>
+
+ <section id='schedulers'>
+ <title>Schedulers</title>
+
+ <para>
+ Variables specific to scheduling functionality exist:
+ <itemizedlist>
+ <listitem><para>
+ <link linkend='var-BB_SCHEDULER'><filename>BB_SCHEDULER</filename></link>
+ </para></listitem>
+ <listitem><para>
+ <link linkend='var-BB_SCHEDULERS'><filename>BB_SCHEDULERS</filename></link>
+ </para></listitem>
+ </itemizedlist>
+ </para>
+ </section>
+ </section>
+
+ <section id='metadata-classes'>
+ <title>Classes</title>
+
+ <para>
+ BitBake's rudimentary inheritance mechanism is accomplished using
+ classes.
+ As briefly mentioned in the metadata introduction, BitBake
+ parses a class when an inherit directive is encountered, and it
+ is located in the <filename>classes</filename> directory
+ relative to the directories in
+ <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
+ </para>
+ </section>
+
+ <section id='recipe-bb-files'>
+ <title>Recipe (<filename>.bb</filename>) Files</title>
+
+ <para>
+ Recipe files, which are files that have the
+ <filename>.bb</filename> file extension, are logical units of
+ tasks for execution.
+ Normally, that logical unit is a package that needs to be
+ built.
+ </para>
+
+ <para>
+ BitBake obeys all inter-recipe dependencies.
+ </para>
+
+ <para>
+ Recipe files must reside in locations found in the
+ <link linkend='var-BBFILES'><filename>BBFILES</filename></link>
+ variable.
+ </para>
+ </section>
+
+ <section id='append-bbappend-files'>
+ <title>Append (<filename>.bbappend</filename>) Files</title>
+
+ <para>
+ Append files, which are files that have the
+ <filename>.bbappend</filename> file extension, add or
+ extend build information to an existing
+ <link linkend='recipe-bb-files'>recipe file</link>.
+ </para>
+
+ <para>
+ BitBake expects every append file to have a corresponding recipe file.
+ Furthermore, the append file and corresponding recipe file
+ must use the same root filename.
+ The filenames can differ only in the file type suffix used
+ (e.g. <filename>formfactor_0.0.bb</filename> and
+ <filename>formfactor_0.0.bbappend</filename>).
+ </para>
+
+ <para>
+ Information in append files overrides the information in the
+ similarly-named recipe file.
+ </para>
+ </section>
+ </section>
+
+ <section id='bitbake-dev-environment'>
+ <title>BitBake</title>
+
+ <para>
+ The OpenEmbedded build system uses BitBake to produce images.
+ BitBake consists of several functional areas.
+ This section takes a closer look at each of those areas.
+ </para>
+
+ <section id='source-fetching-dev-environment'>
+ <title>Source Fetching</title>
+
+ <para>
+ The first stages of building a recipe are to fetch and unpack
+ the source code:
+ <imagedata fileref="figures/source-fetching.png" align="center" width="6.5in" depth="5in" />
+ </para>
+figures/
+ <para>
+ The <filename>do_fetch</filename> and
+ <filename>do_unpack</filename> tasks fetch the source files
+ and unpack them into the work directory.
+ By default, everything is accomplished in the
+ build directory,
+ which has a defined structure.
+ </para>
+
+ <para>
+ Unpacked source files are pointed to by a variable.
+ For example, in the Yocto Project and OpenEmbedded build systems,
+ the <filename>S</filename> variable points to these source files.
+ Each recipe has an area in the Build Directory where the
+ unpacked source code resides.
+ The name of that directory for any given recipe is defined from
+ several different variables.
+ You can see the variables that define these directories
+ by looking at the figure that shows the structure and variables
+ used in the Yocto Project:
+ <itemizedlist>
+ <listitem><para><filename>TMPDIR</filename>
+ </para></listitem>
+ <listitem><para><filename>PACKAGE_ARCH</filename>
+ </para></listitem>
+ <listitem><para><filename>TARGET_OS</filename>
+ </para></listitem>
+ <listitem><para><link linkend='var-PN'><filename>PN</filename></link>
+ </para></listitem>
+ <listitem><para><link linkend='var-PV'><filename>PV</filename></link>
+ </para></listitem>
+ <listitem><para><link linkend='var-PR'><filename>PR</filename></link>
+ </para></listitem>
+ <listitem><para><filename>WORKDIR</filename>
+ </para></listitem>
+ <listitem><para><filename>S</filename>
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ Briefly, the <filename>S</filename> directory contains the
+ unpacked source files for a recipe.
+ The <filename>WORKDIR</filename> directory is where all the
+ building goes on for a given recipe.
+ </para>
+ </section>
+
+ <section id='patching-dev-environment'>
+ <title>Patching</title>
+
+ <para>
+ Once source code is fetched and unpacked, BitBake locates
+ patch files and applies them to the source files:
+ <imagedata fileref="figures/patching.png" align="center" width="6in" depth="5in" />
+ </para>
+
+ <para>
+ The <filename>do_patch</filename> task processes recipes by
+ using the
+ <link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>
+ variable to locate applicable patch files, which by default
+ are <filename>*.patch</filename> or
+ <filename>*.diff</filename> files, or any file if
+ "apply=yes" is specified for the file in
+ <filename>SRC_URI</filename>.
+ </para>
+
+ <para>
+ BitBake finds and applies multiple patches for a single recipe
+ in the order in which it finds the patches.
+ Patches are applied to the recipe's source files located in the
+ <filename>S</filename> directory.
+ </para>
+
+ <para>
+ For more information on how the source directories are
+ created, see the
+ "<link linkend='source-fetching-dev-environment'>Source Fetching</link>"
+ section.
+ </para>
+ </section>
+
+ <section id='configuration-and-compilation-dev-environment'>
+ <title>Configuration and Compilation</title>
+
+ <para>
+ After source code is patched, BitBake executes tasks that
+ configure and compile the source code:
+ <imagedata fileref="figures/configuration-compile-autoreconf.png" align="center" width="7in" depth="5in" />
+ </para>
+
+ <para>
+ This step in the build process consists of three tasks:
+ <itemizedlist>
+ <listitem><para><emphasis><filename>do_configure</filename>:</emphasis>
+ This task configures the source by enabling and
+ disabling any build-time and configuration options for
+ the software being built.
+ Configurations can come from the recipe itself as well
+ as from an inherited class.
+ Additionally, the software itself might configure itself
+ depending on the target for which it is being built.
+ </para>
+
+ <para>The configurations handled by the
+ <filename>do_configure</filename> task are specific
+ to source code configuration for the source code
+ being built by the recipe.</para>
+
+ <para>If you are using the Autotools class
+ (<filename>autotools.bbclass</filename>),
+ you can add additional configuration options by using
+ the <filename>EXTRA_OECONF</filename>
+ variable.
+ For information on how this variable works within
+ that class, see the
+ <filename>meta/classes/autotools.bbclass</filename> file.
+ </para></listitem>
+ <listitem><para><emphasis><filename>do_compile</filename>:</emphasis>
+ Once a configuration task has been satisfied, BitBake
+ compiles the source using the
+ <filename>do_compile</filename> task.
+ Compilation occurs in the directory pointed to by the
+ <link linkend='var-B'><filename>B</filename></link>
+ variable.
+ Realize that the <filename>B</filename> directory is, by
+ default, the same as the
+ <filename>S</filename>
+ directory.</para></listitem>
+ <listitem><para><emphasis><filename>do_install</filename>:</emphasis>
+ Once compilation is done, BitBake executes the
+ <filename>do_install</filename> task.
+ This task copies files from the <filename>B</filename>
+ directory and places them in a holding area pointed to
+ by the <filename>D</filename> variable.</para></listitem>
+ </itemizedlist>
+ </para>
+ </section>
+
+ <section id='package-splitting-dev-environment'>
+ <title>Package Splitting</title>
+
+ <para>
+ After source code is configured and compiled, the
+ OpenEmbedded build system analyzes
+ the results and splits the output into packages:
+ <imagedata fileref="figures/analysis-for-package-splitting.png" align="center" width="7in" depth="7in" />
+ </para>
+
+ <para>
+ The <filename>do_package</filename> and
+ <filename>do_packagedata</filename> tasks combine to analyze
+ the files found in the <filename>D</filename> directory
+ and split them into subsets based on available packages and
+ files.
+ The analyzing process involves the following as well as other
+ items: splitting out debugging symbols,
+ looking at shared library dependencies between packages,
+ and looking at package relationships.
+ The <filename>do_packagedata</filename> task creates package
+ metadata based on the analysis such that the
+ OpenEmbedded build system can generate the final packages.
+ Working, staged, and intermediate results of the analysis
+ and package splitting process use these areas:
+ <itemizedlist>
+ <listitem><para><filename>PKGD</filename>
+ </para></listitem>
+ <listitem><para><filename>PKGDATA_DIR</filename>
+ </para></listitem>
+ <listitem><para><filename>PKGDESTWORK</filename>
+ </para></listitem>
+ <listitem><para><filename>PKGDEST</filename>
+ </para></listitem>
+ </itemizedlist>
+ The <filename>FILES</filename>
+ variable defines the files that go into each package in
+ <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>.
+ If you want details on how this is accomplished in the Yocto Project
+ for example, you can look at the <filename>package.bbclass</filename>
+ file in a Yocto tree.
+ </para>
+
+ <para>
+ Depending on the type of packages being created (RPM, DEB, or
+ IPK), the <filename>do_package_write_*</filename> task
+ creates the actual packages and places them in the
+ Package Feed area, which is
+ <filename>${TMPDIR}/deploy</filename>.
+ <note>
+ Support for creating feeds directly from the
+ <filename>deploy/*</filename> directories does not exist.
+ Creating such feeds usually requires some kind of feed
+ maintenance mechanism that would upload the new packages
+ into an official package feed (e.g. the
+ Ångström distribution).
+ This functionality is highly distribution-specific
+ and thus is not provided out of the box.
+ </note>
+ </para>
+ </section>
+
+ <section id='image-generation-dev-environment'>
+ <title>Image Generation</title>
+
+ <para>
+ Once packages are split and stored in the Package Feeds area,
+ the OpenEmbedded build system uses BitBake to generate the
+ root filesystem image:
+ <imagedata fileref="figures/image-generation.png" align="center" width="6in" depth="7in" />
+ </para>
+
+ <para>
+ The image generation process consists of several stages and
+ depends on many variables.
+ The <filename>do_rootfs</filename> task uses these key variables
+ to help create the list of packages to actually install:
+ <itemizedlist>
+ <listitem><para><filename>IMAGE_INSTALL</filename>:
+ Lists out the base set of packages to install from
+ the Package Feeds area.</para></listitem>
+ <listitem><para><filename>PACKAGE_EXCLUDE</filename>:
+ Specifies packages that should not be installed.
+ </para></listitem>
+ <listitem><para><filename>IMAGE_FEATURES</filename>:
+ Specifies features to include in the image.
+ Most of these features map to additional packages for
+ installation.</para></listitem>
+ <listitem><para><filename>PACKAGE_CLASSES</filename>:
+ Specifies the package backend to use and consequently
+ helps determine where to locate packages within the
+ Package Feeds area.</para></listitem>
+ <listitem><para><filename>IMAGE_LINGUAS</filename>:
+ Determines the language(s) for which additional
+ language support packages are installed.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ Package installation is under control of the package manager
+ (e.g. smart/rpm, opkg, or apt/dpkg) regardless of whether or
+ not package management is enabled for the target.
+ At the end of the process, if package management is not
+ enabled for the target, the package manager's data files
+ are deleted from the root filesystem.
+ </para>
+
+ <para>
+ During image generation, the build system attempts to run
+ all post-installation scripts.
+ Any that fail to run on the build host are run on the
+ target when the target system is first booted.
+ If you are using a
+ read-only root filesystem,
+ all the post installation scripts must succeed during the
+ package installation phase since the root filesystem cannot be
+ written into.
+ </para>
+
+ <para>
+ During Optimization, optimizing processes are run across
+ the image.
+ These processes include <filename>mklibs</filename> and
+ <filename>prelink</filename>.
+ The <filename>mklibs</filename> process optimizes the size
+ of the libraries.
+ A <filename>prelink</filename> process optimizes the dynamic
+ linking of shared libraries to reduce start up time of
+ executables.
+ </para>
+
+ <para>
+ Part of the image generation process includes compressing the
+ root filesystem image.
+ Compression is accomplished through several optimization
+ routines designed to reduce the overall size of the image.
+ </para>
+
+ <para>
+ After the root filesystem has been constructed, the image
+ generation process turns everything into an image file or
+ a set of image files.
+ The formats used for the root filesystem depend on the
+ <filename>IMAGE_FSTYPES</filename> variable.
+ </para>
+
+ <note>
+ The entire image generation process is run under Pseudo.
+ Running under Pseudo ensures that the files in the root
+ filesystem have correct ownership.
+ </note>
+ </section>
+
+ <section id='sdk-generation-dev-environment'>
+ <title>SDK Generation</title>
+
+ <para>
+ The OpenEmbedded build system uses BitBake to generate the
+ Software Development Kit (SDK) installer script:
+ <imagedata fileref="figures/sdk-generation.png" align="center" width="6in" depth="7in" />
+ </para>
+
+ <para>
+ Like image generation, the SDK script process consists of
+ several stages and depends on many variables.
+ The <filename>do_populate_sdk</filename> task uses these
+ key variables to help create the list of packages to actually
+ install.
+ </para>
+
+ <para>
+ The <filename>do_populate_sdk</filename> task handles two
+ parts: a target part and a host part.
+ The target part is the part built for the target hardware and
+ includes libraries and headers.
+ The host part is the part of the SDK that runs on the
+ <filename>SDKMACHINE</filename>.
+ </para>
+
+ <para>
+ Once both parts are constructed, the
+ <filename>do_populate_sdk</filename> task performs some cleanup
+ on both parts.
+ After the cleanup, the task creates a cross-development
+ environment setup script and any configuration files that
+ might be needed.
+ </para>
+
+ <para>
+ The final output of the task is the Cross-development
+ toolchain installation script (<filename>.sh</filename> file),
+ which includes the environment setup script.
+ </para>
+ </section>
+ </section>
+</chapter>
</section>
</section>
- <section id='running-a-task'>
- <title>Running a Task</title>
-
- <para>
- Tasks can either be a shell task or a Python task.
- For shell tasks, BitBake writes a shell script to
- <filename>${WORKDIR}/temp/run.do_taskname.pid</filename>
- and then executes the script.
- The generated shell script contains all the exported variables,
- and the shell functions with all variables expanded.
- Output from the shell script goes to the file
- <filename>${WORKDIR}/temp/log.do_taskname.pid</filename>.
- Looking at the expanded shell functions in the run file and
- the output in the log files is a useful debugging technique.
- </para>
-
- <para>
- For Python tasks, BitBake executes the task internally and logs
- information to the controlling terminal.
- Future versions of BitBake will write the functions to files
- similar to the way shell tasks are handled.
- Logging will be handled in a way similar to shell tasks as well.
- </para>
-
- <para>
- Once all the tasks have been completed BitBake exits.
- </para>
- </section>
-
<section id='variable-flags'>
<title>Variable Flags</title>
</para>
</section>
- <section id='parsing-and-execution'>
- <title>Parsing and Execution</title>
-
- <section id='parsing-overview'>
- <title>Parsing Overview</title>
-
- <para>
- BitBake parses configuration files, classes, recipes, and append
- files.
- </para>
-
- <para>
- The first thing BitBake does is look for the
- <filename>bitbake.conf</filename> file.
- This file resides in the <filename>conf</filename>
- directory, which must be listed in
- <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
- </para>
-
- <para>
- The <filename>bitbake.conf</filename> file lists other configuration
- files to include from the <filename>conf</filename> directory below the
- directories listed in <filename>BBPATH</filename>.
- In general, the most important of these
- configuration files from a user's perspective
- is <filename>local.conf</filename>, which contains the user's
- customized settings for the build environment.
- </para>
-
- <para>
- Other notable configuration files are the distribution configuration
- file and the machine configuration file.
- These configuration files are normally identified by
- variables unique to the build systems using BitBake.
- For example, the Yocto Project uses the
- <filename>DISTRO</filename> and <filename>MACHINE</filename>
- variables, respectively.
- </para>
-
- <para>
- After parsing of the configuration files, some standard classes are
- included.
- The <filename>base.bbclass</filename> file
- is always included.
- Other classes that are specified in the configuration using the
- <link linkend='var-INHERIT'><filename>INHERIT</filename></link>
- variable are also included.
- BitBake searches for class files in a "classes" subdirectory under
- the paths in <filename>BBPATH</filename> in the same way as
- configuration files.
- </para>
-
- <para>
- After classes are included, the variable
- <filename>BBFILES</filename> is set, usually in
- <filename>local.conf</filename>, and defines the list of
- places to search for recipe and append files.
- Adding extra content to <filename>BBFILES</filename> is best
- achieved through the use of BitBake layers.
- </para>
-
- <para>
- BitBake parses each recipe and append file located with
- <filename>BBFILES</filename> and stores the values of various
- variables into the datastore.
- In summary, for each recipe and append file pairing, the configuration
- plus the base class of variables are set, followed by the data in the
- recipe file itself, followed by any inherit commands
- that the recipe file might contain.
- </para>
-
- <para>
- Because parsing recipe and append files is a time consuming
- process, a cache, referred to as the "setscene"
- is kept to speed up subsequent parsing.
- The setscene is invalid if the timestamps of a recipe changes,
- any of the include files change, configuration files change,
- or class files on which the recipe file depends change.
- </para>
- </section>
-
- <section id='parsing-configuration-files'>
- <title>Configuration files</title>
-
- <para>
- Prior to parsing configuration files, Bitbake looks
- at certain variables, including:
- <itemizedlist>
- <listitem><para><link linkend='var-BB_ENV_WHITELIST'><filename>BB_ENV_WHITELIST</filename></link></para></listitem>
- <listitem><para><link linkend='var-BB_PRESERVE_ENV'><filename>BB_PRESERVE_ENV</filename></link></para></listitem>
- <listitem><para><link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link></para></listitem>
- <listitem><para><link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link></para></listitem>
- <listitem><para><link linkend='var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></link></para></listitem>
- <listitem><para><link linkend='var-PREFERRED_PROVIDERS'><filename>PREFERRED_PROVIDERS</filename></link></para></listitem>
- </itemizedlist>
- </para>
-
- <para>
- The first kind of metadata in BitBake is configuration metadata.
- This metadata is global, and therefore affects all packages and
- tasks that are executed.
- </para>
-
- <para>
- BitBake will first search the current working directory for an
- optional <filename>conf/bblayers.conf</filename> configuration file.
- This file is expected to contain a
- <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link>
- variable that is a space delimited list of 'layer' directories.
- For each directory in this list, a <filename>conf/layer.conf</filename>
- file will be searched for and parsed with the
- <link linkend='var-LAYERDIR'><filename>LAYERDIR</filename></link>
- variable being set to the directory where the layer was found.
- The idea is these files will setup
- <link linkend='var-BBPATH'><filename>BBPATH</filename></link>
- and other variables correctly for a given build directory automatically
- for the user.
- </para>
-
- <para>
- BitBake will then expect to find <filename>conf/bitbake.conf</filename>
- file somewhere in the user specified <filename>BBPATH</filename>.
- That configuration file generally has include directives to pull
- in any other metadata (generally files specific to architecture,
- machine, local and so on).
- </para>
-
- <para>
- Only variable definitions and include directives are allowed
- in <filename>.conf</filename> files.
- The following variables include:
- <itemizedlist>
- <listitem><para>
- <link linkend='var-BITBAKE_UI'><filename>BITBAKE_UI</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BBDEBUG'><filename>BBDEBUG</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-MULTI_PROVIDER_WHITELIST'><filename>MULTI_PROVIDER_WHITELIST</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></link>
- </para></listitem>
- <listitem><para>
- <filename>BBPKGS</filename>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BB_DEFAULT_TASK'><filename>BB_DEFAULT_TASK</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BB_VERBOSE_LOGS'><filename>BB_VERBOSE_LOGS</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BB_NICE_LEVEL'><filename>BB_NICE_LEVEL</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BBFILE_COLLECTIONS'><filename>BBFILE_COLLECTIONS</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BB_DANGLINGAPPENDS_WARNONLY'><filename>BB_DANGLINGAPPENDS_WARNONLY</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BBINCLUDED'><filename>BBINCLUDED</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BBFILE_PRIORITY'><filename>BBFILE_PRIORITY</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BUILDNAME'><filename>BUILDNAME</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BBMASK'><filename>BBMASK</filename></link>
- </para></listitem>
- </itemizedlist>
- </para>
-
- <section id='layers'>
- <title>Layers</title>
-
- <para>
- Layers allow you to isolate different types of
- customizations from each other.
- While you might find it tempting to keep everything in one layer
- when working on a single project, the more modular you organize
- your metadata, the easier it is to cope with future changes.
- </para>
-
- <para>
- To illustrate how you can use layers to keep things modular,
- consider machine customizations.
- These types of customizations typically reside in a special layer,
- rather than a general layer, called a Board Specific Package (BSP) Layer.
- Furthermore, the machine customizations should be isolated from
- recipes and metadata that support a new GUI environment, for
- example.
- This situation gives you a couple of layers: one for the machine
- configurations and one for the GUI environment.
- It is important to understand, however, that the BSP layer can still
- make machine-specific additions to recipes within
- the GUI environment layer without polluting the GUI layer itself
- with those machine-specific changes.
- You can accomplish this through a recipe that is a BitBake append
- (<filename>.bbappend</filename>) file.
- </para>
-
- <para>
- There are certain variables specific to layers:
- <itemizedlist>
- <listitem><para>
- <link linkend='var-LAYERDEPENDS'><filename>LAYERDEPENDS</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-LAYERVERSION'><filename>LAYERVERSION</filename></link>
- </para></listitem>
- </itemizedlist>
- </para>
- </section>
-
- <section id='schedulers'>
- <title>Schedulers</title>
-
- <para>
- Variables specific to scheduling functionality exist:
- <itemizedlist>
- <listitem><para>
- <link linkend='var-BB_SCHEDULER'><filename>BB_SCHEDULER</filename></link>
- </para></listitem>
- <listitem><para>
- <link linkend='var-BB_SCHEDULERS'><filename>BB_SCHEDULERS</filename></link>
- </para></listitem>
- </itemizedlist>
- </para>
- </section>
- </section>
-
- <section id='metadata-classes'>
- <title>Classes</title>
-
- <para>
- BitBake's rudimentary inheritance mechanism is accomplished using
- classes.
- As briefly mentioned in the metadata introduction, BitBake
- parses a class when an inherit directive is encountered, and it
- is located in the <filename>classes</filename> directory
- relative to the directories in
- <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
- </para>
- </section>
-
- <section id='recipe-bb-files'>
- <title>Recipe (<filename>.bb</filename>) Files</title>
-
- <para>
- Recipe files, which are files that have the
- <filename>.bb</filename> file extension, are logical units of
- tasks for execution.
- Normally, that logical unit is a package that needs to be
- built.
- </para>
-
- <para>
- BitBake obeys all inter-recipe dependencies.
- </para>
-
- <para>
- Recipe files must reside in locations found in the
- <link linkend='var-BBFILES'><filename>BBFILES</filename></link>
- variable.
- </para>
- </section>
-
- <section id='append-bbappend-files'>
- <title>Append (<filename>.bbappend</filename>) Files</title>
-
- <para>
- Append files, which are files that have the
- <filename>.bbappend</filename> file extension, add or
- extend build information to an existing
- <link linkend='recipe-bb-files'>recipe file</link>.
- </para>
-
- <para>
- BitBake expects every append file to have a corresponding recipe file.
- Furthermore, the append file and corresponding recipe file
- must use the same root filename.
- The filenames can differ only in the file type suffix used
- (e.g. <filename>formfactor_0.0.bb</filename> and
- <filename>formfactor_0.0.bbappend</filename>).
- </para>
-
- <para>
- Information in append files overrides the information in the
- similarly-named recipe file.
- </para>
- </section>
- </section>
-
<section id='events'>
<title>Events</title>
projects / thirdparty / openembedded / openembedded-core-contrib.git / commitdiff
