722 lines
35 KiB
XML
722 lines
35 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="bitbake-user-manual-intro">
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<title>Overview</title>
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<para>
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Welcome to the BitBake User Manual.
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This manual provides information on the BitBake tool.
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The information attempts to be as independent as possible regarding
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systems that use BitBake, such as OpenEmbedded and the
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Yocto Project.
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In some cases, scenarios or examples within the context of
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a build system are used in the manual to help with understanding.
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For these cases, the manual clearly states the context.
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</para>
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<section id="intro">
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<title>Introduction</title>
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<para>
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Fundamentally, BitBake is a generic task execution
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engine that allows shell and Python tasks to be run
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efficiently and in parallel while working within
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complex inter-task dependency constraints.
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One of BitBake's main users, OpenEmbedded, takes this core
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and builds embedded Linux software stacks using
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a task-oriented approach.
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</para>
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<para>
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Conceptually, BitBake is similar to GNU Make in
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some regards but has significant differences:
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<itemizedlist>
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<listitem><para>
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BitBake executes tasks according to provided
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metadata that builds up the tasks.
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Metadata is stored in recipe (<filename>.bb</filename>)
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and related recipe "append" (<filename>.bbappend</filename>)
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files, configuration (<filename>.conf</filename>) and
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underlying include (<filename>.inc</filename>) files, and
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in class (<filename>.bbclass</filename>) files.
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The metadata provides
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BitBake with instructions on what tasks to run and
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the dependencies between those tasks.
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</para></listitem>
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<listitem><para>
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BitBake includes a fetcher library for obtaining source
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code from various places such as local files, source control
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systems, or websites.
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</para></listitem>
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<listitem><para>
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The instructions for each unit to be built (e.g. a piece
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of software) are known as "recipe" files and
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contain all the information about the unit
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(dependencies, source file locations, checksums, description
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and so on).
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</para></listitem>
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<listitem><para>
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BitBake includes a client/server abstraction and can
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be used from a command line or used as a service over
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XML-RPC and has several different user interfaces.
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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 id="history-and-goals">
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<title>History and Goals</title>
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<para>
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BitBake was originally a part of the OpenEmbedded project.
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It was inspired by the Portage package management system
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used by the Gentoo Linux distribution.
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On December 7, 2004, OpenEmbedded project team member
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Chris Larson split the project into two distinct pieces:
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<itemizedlist>
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<listitem><para>BitBake, a generic task executor</para></listitem>
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<listitem><para>OpenEmbedded, a metadata set utilized by
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BitBake</para></listitem>
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</itemizedlist>
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Today, BitBake is the primary basis of the
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<ulink url="http://www.openembedded.org/">OpenEmbedded</ulink>
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project, which is being used to build and maintain Linux
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distributions such as the
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<ulink url='http://www.angstrom-distribution.org/'>Angstrom Distribution</ulink>,
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and which is also being used as the build tool for Linux projects
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such as the
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<ulink url='http://www.yoctoproject.org'>Yocto Project</ulink>.
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</para>
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<para>
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Prior to BitBake, no other build tool adequately met the needs of
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an aspiring embedded Linux distribution.
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All of the build systems used by traditional desktop Linux
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distributions lacked important functionality, and none of the
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ad hoc Buildroot-based systems, prevalent in the
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embedded space, were scalable or maintainable.
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</para>
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<para>
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Some important original goals for BitBake were:
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<itemizedlist>
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<listitem><para>
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Handle cross-compilation.
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</para></listitem>
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<listitem><para>
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Handle inter-package dependencies (build time on
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target architecture, build time on native
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architecture, and runtime).
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</para></listitem>
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<listitem><para>
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Support running any number of tasks within a given
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package, including, but not limited to, fetching
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upstream sources, unpacking them, patching them,
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configuring them, and so forth.
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</para></listitem>
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<listitem><para>
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Be Linux distribution agnostic for both build and
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target systems.
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</para></listitem>
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<listitem><para>
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Be architecture agnostic.
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</para></listitem>
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<listitem><para>
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Support multiple build and target operating systems
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(e.g. Cygwin, the BSDs, and so forth).
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</para></listitem>
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<listitem><para>
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Be self contained, rather than tightly
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integrated into the build machine's root
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filesystem.
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</para></listitem>
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<listitem><para>
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Handle conditional metadata on the target architecture,
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operating system, distribution, and machine.
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</para></listitem>
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<listitem><para>
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Be easy to use the tools to supply local metadata and packages
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against which to operate.
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</para></listitem>
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<listitem><para>
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Be easy to use BitBake to collaborate between multiple
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projects for their builds.
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</para></listitem>
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<listitem><para>
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Provide an inheritance mechanism to share
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common metadata between many packages.
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</para></listitem>
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</itemizedlist>
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Over time it became apparent that some further requirements
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were necessary:
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<itemizedlist>
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<listitem><para>
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Handle variants of a base recipe (e.g. native, sdk,
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and multilib).
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</para></listitem>
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<listitem><para>
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Split metadata into layers and allow layers
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to enhance or override other layers.
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</para></listitem>
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<listitem><para>
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Allow representation of a given set of input variables
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to a task as a checksum.
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Based on that checksum, allow acceleration of builds
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with prebuilt components.
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</para></listitem>
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</itemizedlist>
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BitBake satisfies all the original requirements and many more
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with extensions being made to the basic functionality to
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reflect the additional requirements.
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Flexibility and power have always been the priorities.
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BitBake is highly extensible and supports embedded Python code and
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execution of any arbitrary tasks.
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</para>
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</section>
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<section id="Concepts">
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<title>Concepts</title>
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<para>
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BitBake is a program written in the Python language.
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At the highest level, BitBake interprets metadata, decides
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what tasks are required to run, and executes those tasks.
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Similar to GNU Make, BitBake controls how software is
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built.
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GNU Make achieves its control through "makefiles", while
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BitBake uses "recipes".
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</para>
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<para>
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BitBake extends the capabilities of a simple
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tool like GNU Make by allowing for the definition of much more
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complex tasks, such as assembling entire embedded Linux
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distributions.
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</para>
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<para>
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The remainder of this section introduces several concepts
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that should be understood in order to better leverage
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the power of BitBake.
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</para>
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<section id='recipes'>
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<title>Recipes</title>
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<para>
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BitBake Recipes, which are denoted by the file extension
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<filename>.bb</filename>, are the most basic metadata files.
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These recipe files provide BitBake with the following:
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<itemizedlist>
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<listitem><para>Descriptive information about the
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package (author, homepage, license, and so on)</para></listitem>
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<listitem><para>The version of the recipe</para></listitem>
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<listitem><para>Existing dependencies (both build
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and runtime dependencies)</para></listitem>
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<listitem><para>Where the source code resides and
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how to fetch it</para></listitem>
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<listitem><para>Whether the source code requires
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any patches, where to find them, and how to apply
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them</para></listitem>
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<listitem><para>How to configure and compile the
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source code</para></listitem>
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<listitem><para>Where on the target machine to install the
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package or packages created</para></listitem>
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</itemizedlist>
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</para>
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<para>
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Within the context of BitBake, or any project utilizing BitBake
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as its build system, files with the <filename>.bb</filename>
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extension are referred to as recipes.
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<note>
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The term "package" is also commonly used to describe recipes.
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However, since the same word is used to describe packaged
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output from a project, it is best to maintain a single
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descriptive term - "recipes".
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Put another way, a single "recipe" file is quite capable
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of generating a number of related but separately installable
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"packages".
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In fact, that ability is fairly common.
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</note>
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</para>
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</section>
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<section id='configuration-files'>
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<title>Configuration Files</title>
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<para>
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Configuration files, which are denoted by the
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<filename>.conf</filename> extension, define
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various configuration variables that govern the project's build
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process.
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These files fall into several areas that define
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machine configuration options, distribution configuration
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options, compiler tuning options, general common
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configuration options, and user configuration options.
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The main configuration file is the sample
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<filename>bitbake.conf</filename> file, which is
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located within the BitBake source tree
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<filename>conf</filename> directory.
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</para>
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</section>
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<section id='classes'>
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<title>Classes</title>
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<para>
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Class files, which are denoted by the
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<filename>.bbclass</filename> extension, contain
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information that is useful to share between metadata files.
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The BitBake source tree currently comes with one class metadata file
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called <filename>base.bbclass</filename>.
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You can find this file in the
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<filename>classes</filename> directory.
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The <filename>base.bbclass</filename> class files is special since it
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is always included automatically for all recipes
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and classes.
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This class contains definitions for standard basic tasks such
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as fetching, unpacking, configuring (empty by default),
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compiling (runs any Makefile present), installing (empty by
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default) and packaging (empty by default).
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These tasks are often overridden or extended by other classes
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added during the project development process.
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</para>
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</section>
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<section id='layers'>
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<title>Layers</title>
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<para>
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Layers allow you to isolate different types of
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customizations from each other.
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While you might find it tempting to keep everything in one layer
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when working on a single project, the more modular you organize
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your metadata, the easier it is to cope with future changes.
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</para>
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<para>
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To illustrate how you can use layers to keep things modular,
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consider customizations you might make to support a specific target machine.
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These types of customizations typically reside in a special layer,
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rather than a general layer, called a Board Support Package (BSP)
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Layer.
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Furthermore, the machine customizations should be isolated from
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recipes and metadata that support a new GUI environment, for
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example.
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This situation gives you a couple of layers: one for the machine
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configurations and one for the GUI environment.
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It is important to understand, however, that the BSP layer can still
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make machine-specific additions to recipes within
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the GUI environment layer without polluting the GUI layer itself
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with those machine-specific changes.
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You can accomplish this through a recipe that is a BitBake append
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(<filename>.bbappend</filename>) file.
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</para>
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</section>
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<section id='append-bbappend-files'>
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<title>Append Files</title>
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<para>
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Append files, which are files that have the
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<filename>.bbappend</filename> file extension, extend or
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override information in an existing recipe file.
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</para>
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<para>
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BitBake expects every append file to have a corresponding recipe file.
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Furthermore, the append file and corresponding recipe file
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must use the same root filename.
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The filenames can differ only in the file type suffix used
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(e.g. <filename>formfactor_0.0.bb</filename> and
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<filename>formfactor_0.0.bbappend</filename>).
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</para>
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<para>
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Information in append files extends or
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overrides the information in the underlying,
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similarly-named recipe files.
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</para>
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<para>
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When you name an append file, you can use the
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wildcard character (%) to allow for matching recipe names.
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For example, suppose you have an append file named
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as follows:
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<literallayout class='monospaced'>
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busybox_1.21.%.bbappend
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</literallayout>
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That append file would match any <filename>busybox_1.21.x.bb</filename>
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version of the recipe.
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So, the append file would match the following recipe names:
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<literallayout class='monospaced'>
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busybox_1.21.1.bb
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busybox_1.21.2.bb
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busybox_1.21.3.bb
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</literallayout>
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If the <filename>busybox</filename> recipe was updated to
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<filename>busybox_1.3.0.bb</filename>, the append name would not
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match.
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However, if you named the append file
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<filename>busybox_1.%.bbappend</filename>, then you would have a match.
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</para>
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<para>
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In the most general case, you could name the append file something as
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simple as <filename>busybox_%.bbappend</filename> to be entirely
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version independent.
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</para>
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</section>
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</section>
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<section id='obtaining-bitbake'>
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<title>Obtaining BitBake</title>
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<para>
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You can obtain BitBake several different ways:
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<itemizedlist>
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<listitem><para><emphasis>Cloning BitBake:</emphasis>
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Using Git to clone the BitBake source code repository
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is the recommended method for obtaining BitBake.
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Cloning the repository makes it easy to get bug fixes
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and have access to stable branches and the master
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branch.
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Once you have cloned BitBake, you should use
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the latest stable
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branch for development since the master branch is for
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BitBake development and might contain less stable changes.
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</para>
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<para>You usually need a version of BitBake
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that matches the metadata you are using.
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The metadata is generally backwards compatible but
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not forward compatible.</para>
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<para>Here is an example that clones the BitBake repository:
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<literallayout class='monospaced'>
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$ git clone git://git.openembedded.org/bitbake
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</literallayout>
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This command clones the BitBake Git repository into a
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directory called <filename>bitbake</filename>.
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Alternatively, you can
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designate a directory after the
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<filename>git clone</filename> command
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if you want to call the new directory something
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other than <filename>bitbake</filename>.
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Here is an example that names the directory
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<filename>bbdev</filename>:
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<literallayout class='monospaced'>
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$ git clone git://git.openembedded.org/bitbake bbdev
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</literallayout></para></listitem>
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<listitem><para><emphasis>Installation using your Distribution
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Package Management System:</emphasis>
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This method is not
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recommended because the BitBake version that is
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provided by your distribution, in most cases,
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is several
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releases behind a snapshot of the BitBake repository.
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</para></listitem>
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<listitem><para><emphasis>Taking a snapshot of BitBake:</emphasis>
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Downloading a snapshot of BitBake from the
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source code repository gives you access to a known
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branch or release of BitBake.
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<note>
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Cloning the Git repository, as described earlier,
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is the preferred method for getting BitBake.
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Cloning the repository makes it easier to update as
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patches are added to the stable branches.
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</note></para>
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<para>The following example downloads a snapshot of
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BitBake version 1.17.0:
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<literallayout class='monospaced'>
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$ wget http://git.openembedded.org/bitbake/snapshot/bitbake-1.17.0.tar.gz
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$ tar zxpvf bitbake-1.17.0.tar.gz
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</literallayout>
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After extraction of the tarball using the tar utility,
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you have a directory entitled
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<filename>bitbake-1.17.0</filename>.
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</para></listitem>
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<listitem><para><emphasis>Using the BitBake that Comes With Your
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Build Checkout:</emphasis>
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A final possibility for getting a copy of BitBake is that it
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already comes with your checkout of a larger Bitbake-based build
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system, such as Poky.
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Rather than manually checking out individual layers and
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gluing them together yourself, you can check
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out an entire build system.
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The checkout will already include a version of BitBake that
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has been thoroughly tested for compatibility with the other
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components.
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For information on how to check out a particular BitBake-based
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build system, consult that build system's supporting documentation.
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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 id="bitbake-user-manual-command">
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<title>The BitBake Command</title>
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<para>
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The <filename>bitbake</filename> command is the primary interface
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to the BitBake tool.
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This section presents the BitBake command syntax and provides
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several execution examples.
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</para>
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<section id='usage-and-syntax'>
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<title>Usage and syntax</title>
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<para>
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Following is the usage and syntax for BitBake:
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<literallayout class='monospaced'>
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$ bitbake -h
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Usage: bitbake [options] [recipename/target recipe:do_task ...]
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Executes the specified task (default is 'build') for a given set of target recipes (.bb files).
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It is assumed there is a conf/bblayers.conf available in cwd or in BBPATH which
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will provide the layer, BBFILES and other configuration information.
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Options:
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--version show program's version number and exit
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-h, --help show this help message and exit
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-b BUILDFILE, --buildfile=BUILDFILE
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Execute tasks from a specific .bb recipe directly.
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WARNING: Does not handle any dependencies from other
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recipes.
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-k, --continue Continue as much as possible after an error. While the
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target that failed and anything depending on it cannot
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be built, as much as possible will be built before
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stopping.
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-a, --tryaltconfigs Continue with builds by trying to use alternative
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providers where possible.
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-f, --force Force the specified targets/task to run (invalidating
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any existing stamp file).
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-c CMD, --cmd=CMD Specify the task to execute. The exact options
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available depend on the metadata. Some examples might
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be 'compile' or 'populate_sysroot' or 'listtasks' may
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give a list of the tasks available.
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-C INVALIDATE_STAMP, --clear-stamp=INVALIDATE_STAMP
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Invalidate the stamp for the specified task such as
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'compile' and then run the default task for the
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specified target(s).
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-r PREFILE, --read=PREFILE
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Read the specified file before bitbake.conf.
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-R POSTFILE, --postread=POSTFILE
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Read the specified file after bitbake.conf.
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-v, --verbose Enable tracing of shell tasks (with 'set -x').
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Also print bb.note(...) messages to stdout (in
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addition to writing them to ${T}/log.do_<task>).
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|
-D, --debug Increase the debug level. You can specify this
|
|
more than once. -D sets the debug level to 1,
|
|
where only bb.debug(1, ...) messages are printed
|
|
to stdout; -DD sets the debug level to 2, where
|
|
both bb.debug(1, ...) and bb.debug(2, ...)
|
|
messages are printed; etc. Without -D, no debug
|
|
messages are printed. Note that -D only affects
|
|
output to stdout. All debug messages are written
|
|
to ${T}/log.do_taskname, regardless of the debug
|
|
level.
|
|
-n, --dry-run Don't execute, just go through the motions.
|
|
-S SIGNATURE_HANDLER, --dump-signatures=SIGNATURE_HANDLER
|
|
Dump out the signature construction information, with
|
|
no task execution. The SIGNATURE_HANDLER parameter is
|
|
passed to the handler. Two common values are none and
|
|
printdiff but the handler may define more/less. none
|
|
means only dump the signature, printdiff means compare
|
|
the dumped signature with the cached one.
|
|
-p, --parse-only Quit after parsing the BB recipes.
|
|
-s, --show-versions Show current and preferred versions of all recipes.
|
|
-e, --environment Show the global or per-recipe environment complete
|
|
with information about where variables were
|
|
set/changed.
|
|
-g, --graphviz Save dependency tree information for the specified
|
|
targets in the dot syntax.
|
|
-I EXTRA_ASSUME_PROVIDED, --ignore-deps=EXTRA_ASSUME_PROVIDED
|
|
Assume these dependencies don't exist and are already
|
|
provided (equivalent to ASSUME_PROVIDED). Useful to
|
|
make dependency graphs more appealing
|
|
-l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS
|
|
Show debug logging for the specified logging domains
|
|
-P, --profile Profile the command and save reports.
|
|
-u UI, --ui=UI The user interface to use (taskexp, knotty or
|
|
ncurses - default knotty).
|
|
-t SERVERTYPE, --servertype=SERVERTYPE
|
|
Choose which server type to use (process or xmlrpc -
|
|
default process).
|
|
--token=XMLRPCTOKEN Specify the connection token to be used when
|
|
connecting to a remote server.
|
|
--revisions-changed Set the exit code depending on whether upstream
|
|
floating revisions have changed or not.
|
|
--server-only Run bitbake without a UI, only starting a server
|
|
(cooker) process.
|
|
-B BIND, --bind=BIND The name/address for the bitbake server to bind to.
|
|
--no-setscene Do not run any setscene tasks. sstate will be ignored
|
|
and everything needed, built.
|
|
--setscene-only Only run setscene tasks, don't run any real tasks.
|
|
--remote-server=REMOTE_SERVER
|
|
Connect to the specified server.
|
|
-m, --kill-server Terminate the remote server.
|
|
--observe-only Connect to a server as an observing-only client.
|
|
--status-only Check the status of the remote bitbake server.
|
|
-w WRITEEVENTLOG, --write-log=WRITEEVENTLOG
|
|
Writes the event log of the build to a bitbake event
|
|
json file. Use '' (empty string) to assign the name
|
|
automatically.
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='bitbake-examples'>
|
|
<title>Examples</title>
|
|
|
|
<para>
|
|
This section presents some examples showing how to use BitBake.
|
|
</para>
|
|
|
|
<section id='example-executing-a-task-against-a-single-recipe'>
|
|
<title>Executing a Task Against a Single Recipe</title>
|
|
|
|
<para>
|
|
Executing tasks for a single recipe file is relatively simple.
|
|
You specify the file in question, and BitBake parses
|
|
it and executes the specified task.
|
|
If you do not specify a task, BitBake executes the default
|
|
task, which is "build”.
|
|
BitBake obeys inter-task dependencies when doing
|
|
so.
|
|
</para>
|
|
|
|
<para>
|
|
The following command runs the build task, which is
|
|
the default task, on the <filename>foo_1.0.bb</filename>
|
|
recipe file:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -b foo_1.0.bb
|
|
</literallayout>
|
|
The following command runs the clean task on the
|
|
<filename>foo.bb</filename> recipe file:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -b foo.bb -c clean
|
|
</literallayout>
|
|
<note>
|
|
The "-b" option explicitly does not handle recipe
|
|
dependencies.
|
|
Other than for debugging purposes, it is instead
|
|
recommended that you use the syntax presented in the
|
|
next section.
|
|
</note>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='executing-tasks-against-a-set-of-recipe-files'>
|
|
<title>Executing Tasks Against a Set of Recipe Files</title>
|
|
|
|
<para>
|
|
There are a number of additional complexities introduced
|
|
when one wants to manage multiple <filename>.bb</filename>
|
|
files.
|
|
Clearly there needs to be a way to tell BitBake what
|
|
files are available and, of those, which you
|
|
want to execute.
|
|
There also needs to be a way for each recipe
|
|
to express its dependencies, both for build-time and
|
|
runtime.
|
|
There must be a way for you to express recipe preferences
|
|
when multiple recipes provide the same functionality, or when
|
|
there are multiple versions of a recipe.
|
|
</para>
|
|
|
|
<para>
|
|
The <filename>bitbake</filename> command, when not using
|
|
"--buildfile" or "-b" only accepts a "PROVIDES".
|
|
You cannot provide anything else.
|
|
By default, a recipe file generally "PROVIDES" its
|
|
"packagename" as shown in the following example:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake foo
|
|
</literallayout>
|
|
This next example "PROVIDES" the package name and also uses
|
|
the "-c" option to tell BitBake to just execute the
|
|
<filename>do_clean</filename> task:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -c clean foo
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='executing-a-list-of-task-and-recipe-combinations'>
|
|
<title>Executing a List of Task and Recipe Combinations</title>
|
|
|
|
<para>
|
|
The BitBake command line supports specifying different
|
|
tasks for individual targets when you specify multiple
|
|
targets.
|
|
For example, suppose you had two targets (or recipes)
|
|
<filename>myfirstrecipe</filename> and
|
|
<filename>mysecondrecipe</filename> and you needed
|
|
BitBake to run <filename>taskA</filename> for the first
|
|
recipe and <filename>taskB</filename> for the second
|
|
recipe:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake myfirstrecipe:do_taskA mysecondrecipe:do_taskB
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='generating-dependency-graphs'>
|
|
<title>Generating Dependency Graphs</title>
|
|
|
|
<para>
|
|
BitBake is able to generate dependency graphs using
|
|
the <filename>dot</filename> syntax.
|
|
You can convert these graphs into images using the
|
|
<filename>dot</filename> tool from
|
|
<ulink url='http://www.graphviz.org'>Graphviz</ulink>.
|
|
</para>
|
|
|
|
<para>
|
|
When you generate a dependency graph, BitBake writes three files
|
|
to the current working directory:
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
<emphasis><filename>recipe-depends.dot</filename>:</emphasis>
|
|
Shows dependencies between recipes (i.e. a collapsed version of
|
|
<filename>task-depends.dot</filename>).
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<emphasis><filename>task-depends.dot</filename>:</emphasis>
|
|
Shows dependencies between tasks.
|
|
These dependencies match BitBake's internal task execution list.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<emphasis><filename>pn-buildlist</filename>:</emphasis>
|
|
Shows a simple list of targets that are to be built.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
To stop depending on common depends, use the "-I" depend
|
|
option and BitBake omits them from the graph.
|
|
Leaving this information out can produce more readable graphs.
|
|
This way, you can remove from the graph
|
|
<filename>DEPENDS</filename> from inherited classes
|
|
such as <filename>base.bbclass</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
Here are two examples that create dependency graphs.
|
|
The second example omits depends common in OpenEmbedded from
|
|
the graph:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -g foo
|
|
|
|
$ bitbake -g -I virtual/kernel -I eglibc foo
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
</chapter>
|