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Fixes [YOCTO #12370] Moved the "Cross-Development Toolchain Generation" section from the ref-manual to the overview-manual into the concepts chapter. This information is conceptual and now needs to live in the concepts chapter of the new overview-manual. Moving the section caused a few links to have to be fixed in the ref-manual. There was also a figure in the section. So, I had to move the figure from the ref-manual to the overview-manual "figures" folder and update the Makefile for the TARFILE generation. (From yocto-docs rev: 1f3ee5ab308cbe6bd7194086026db397b67ca7c4) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
437 lines
24 KiB
XML
437 lines
24 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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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='ref-terms'>
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<title>Yocto Project Terms</title>
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<para>
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Following is a list of terms and definitions users new to the Yocto
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Project development environment might find helpful.
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While some of these terms are universal, the list includes them
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just in case:
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<itemizedlist>
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<listitem><para>
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<emphasis>Append Files:</emphasis>
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Files that append build information to a recipe file.
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Append files are known as BitBake append files and
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<filename>.bbappend</filename> files.
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The OpenEmbedded build system expects every append file to have
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a corresponding recipe (<filename>.bb</filename>) 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.
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<filename>formfactor_0.0.bb</filename> and
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<filename>formfactor_0.0.bbappend</filename>).</para>
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<para>Information in append files extends or overrides the
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information in the similarly-named recipe file.
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For an example of an append file in use, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
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section in the Yocto Project Development Tasks Manual.
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<note>
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Append files can also use wildcard patterns in their
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version numbers so they can be applied to more than one
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version of the underlying recipe file.
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</note>
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</para></listitem>
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<listitem><para id='bitbake-term'>
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<emphasis>BitBake:</emphasis>
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The task executor and scheduler used by the OpenEmbedded build
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system to build images.
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For more information on BitBake, see the
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<ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
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</para></listitem>
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<listitem><para id='board-support-package-bsp-term'>
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<emphasis>Board Support Package (BSP):</emphasis>
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A group of drivers, definitions, and other components that
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provide support for a specific hardware configuration.
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For more information on BSPs, see the
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<ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
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</para></listitem>
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<listitem>
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<para id='build-directory'>
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<emphasis>Build Directory:</emphasis>
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This term refers to the area used by the OpenEmbedded build
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system for builds.
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The area is created when you <filename>source</filename> the
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setup environment script that is found in the Source Directory
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(i.e. <link linkend='structure-core-script'><filename>&OE_INIT_FILE;</filename></link>).
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The
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<link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
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variable points to the Build Directory.</para>
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<para>You have a lot of flexibility when creating the Build
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Directory.
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Following are some examples that show how to create the
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directory.
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The examples assume your
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<link linkend='source-directory'>Source Directory</link> is
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named <filename>poky</filename>:
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<itemizedlist>
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<listitem><para>Create the Build Directory inside your
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Source Directory and let the name of the Build
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Directory default to <filename>build</filename>:
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<literallayout class='monospaced'>
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$ cd $HOME/poky
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$ source &OE_INIT_FILE;
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</literallayout>
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</para></listitem>
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<listitem><para>Create the Build Directory inside your
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home directory and specifically name it
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<filename>test-builds</filename>:
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<literallayout class='monospaced'>
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$ cd $HOME
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$ source poky/&OE_INIT_FILE; test-builds
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</literallayout>
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</para></listitem>
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<listitem><para>
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Provide a directory path and specifically name the
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Build Directory.
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Any intermediate folders in the pathname must exist.
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This next example creates a Build Directory named
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<filename>YP-&POKYVERSION;</filename>
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in your home directory within the existing
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directory <filename>mybuilds</filename>:
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<literallayout class='monospaced'>
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$cd $HOME
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$ source $HOME/poky/&OE_INIT_FILE; $HOME/mybuilds/YP-&POKYVERSION;
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</literallayout>
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</para></listitem>
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</itemizedlist>
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<note>
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By default, the Build Directory contains
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<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>,
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which is a temporary directory the build system uses for
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its work.
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<filename>TMPDIR</filename> cannot be under NFS.
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Thus, by default, the Build Directory cannot be under NFS.
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However, if you need the Build Directory to be under NFS,
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you can set this up by setting <filename>TMPDIR</filename>
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in your <filename>local.conf</filename> file
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to use a local drive.
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Doing so effectively separates <filename>TMPDIR</filename>
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from <filename>TOPDIR</filename>, which is the Build
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Directory.
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</note>
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</para></listitem>
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<listitem><para id='hardware-build-system-term'>
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<emphasis>Build System:</emphasis>
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The system used to build images in a Yocto Project
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Development environment.
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The build system is sometimes referred to as the
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development host.
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</para></listitem>
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<listitem><para>
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<emphasis>Classes:</emphasis>
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Files that provide for logic encapsulation and inheritance so
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that commonly used patterns can be defined once and then
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easily used in multiple recipes.
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For reference information on the Yocto Project classes, see the
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"<link linkend='ref-classes'>Classes</link>" chapter.
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Class files end with the <filename>.bbclass</filename>
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filename extension.
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</para></listitem>
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<listitem><para>
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<emphasis>Configuration File:</emphasis>
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Configuration information in various <filename>.conf</filename>
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files provides global definitions of variables.
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The <filename>conf/local.conf</filename> configuration file in
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the
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<link linkend='build-directory'>Build Directory</link>
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contains user-defined variables that affect every build.
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The <filename>meta-poky/conf/distro/poky.conf</filename>
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configuration file defines Yocto "distro" configuration
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variables used only when building with this policy.
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Machine configuration files, which
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are located throughout the
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<link linkend='source-directory'>Source Directory</link>, define
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variables for specific hardware and are only used when building
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for that target (e.g. the
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<filename>machine/beaglebone.conf</filename> configuration
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file defines variables for the Texas Instruments ARM Cortex-A8
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development board).
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Configuration files end with a <filename>.conf</filename>
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filename extension.
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</para></listitem>
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<listitem><para id='cross-development-toolchain'>
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<emphasis>Cross-Development Toolchain:</emphasis>
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In general, a cross-development toolchain is a collection of
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software development tools and utilities that run on one
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architecture and allow you to develop software for a
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different, or targeted, architecture.
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These toolchains contain cross-compilers, linkers, and
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debuggers that are specific to the target architecture.</para>
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<para>The Yocto Project supports two different cross-development
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toolchains:
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<itemizedlist>
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<listitem><para>
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A toolchain only used by and within
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BitBake when building an image for a target
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architecture.
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</para></listitem>
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<listitem><para>A relocatable toolchain used outside of
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BitBake by developers when developing applications
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that will run on a targeted device.
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</para></listitem>
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</itemizedlist></para>
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<para>Creation of these toolchains is simple and automated.
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For information on toolchain concepts as they apply to the
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Yocto Project, see the
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"<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>"
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section in the Yocto Project Overview Manual.
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You can also find more information on using the
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relocatable toolchain in the
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<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Application Development and the Extensible Software Development Kit (eSDK)</ulink>
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manual.
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</para></listitem>
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<listitem><para>
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<emphasis>Image:</emphasis>
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An image is an artifact of the BitBake build process given
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a collection of recipes and related Metadata.
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Images are the binary output that run on specific hardware or
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QEMU and are used for specific use-cases.
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For a list of the supported image types that the Yocto Project
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provides, see the
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"<link linkend='ref-images'>Images</link>"
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chapter.
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</para></listitem>
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<listitem><para>
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<emphasis>Layer:</emphasis>
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A collection of recipes representing the core,
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a BSP, or an application stack.
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For a discussion specifically on BSP Layers, see the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
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section in the Yocto Project Board Support Packages (BSP)
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Developer's Guide.
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</para></listitem>
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<listitem><para id='metadata'>
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<emphasis>Metadata:</emphasis>
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The files that BitBake parses when building an image.
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In general, Metadata includes recipes, classes, and
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configuration files.
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In the context of the kernel ("kernel Metadata"), the
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term refers to the kernel config fragments and features
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contained in the
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<ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache'><filename>yocto-kernel-cache</filename></ulink>
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Git repository.
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</para></listitem>
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<listitem><para id='oe-core'>
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<emphasis>OE-Core:</emphasis>
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A core set of Metadata originating with OpenEmbedded (OE)
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that is shared between OE and the Yocto Project.
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This Metadata is found in the <filename>meta</filename>
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directory of the
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<link linkend='source-directory'>Source Directory</link>.
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</para></listitem>
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<listitem><para id='build-system-term'>
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<emphasis>OpenEmbedded Build System:</emphasis>
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The build system specific to the Yocto Project.
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The OpenEmbedded build system is based on another project known
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as "Poky", which uses
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<link linkend='bitbake-term'>BitBake</link> as the task
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executor.
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Throughout the Yocto Project documentation set, the
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OpenEmbedded build system is sometimes referred to simply
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as "the build system".
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If other build systems, such as a host or target build system
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are referenced, the documentation clearly states the
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difference.
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<note>
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For some historical information about Poky, see the
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<link linkend='poky'>Poky</link> term.
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</note>
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</para></listitem>
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<listitem><para>
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<emphasis>Package:</emphasis>
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In the context of the Yocto Project, this term refers to a
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recipe's packaged output produced by BitBake (i.e. a
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"baked recipe").
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A package is generally the compiled binaries produced from the
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recipe's sources.
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You "bake" something by running it through BitBake.</para>
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<para>It is worth noting that the term "package" can,
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in general, have subtle meanings.
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For example, the packages referred to in the
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"<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>"
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section in the Yocto Project Quick Start are compiled binaries
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that, when installed, add functionality to your Linux
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distribution.</para>
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<para>Another point worth noting is that historically within
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the Yocto Project, recipes were referred to as packages - thus,
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the existence of several BitBake variables that are seemingly
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mis-named,
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(e.g. <link linkend='var-PR'><filename>PR</filename></link>,
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<link linkend='var-PV'><filename>PV</filename></link>, and
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<link linkend='var-PE'><filename>PE</filename></link>).
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</para></listitem>
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<listitem><para>
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<emphasis>Package Groups:</emphasis>
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Arbitrary groups of software Recipes.
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You use package groups to hold recipes that, when built,
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usually accomplish a single task.
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For example, a package group could contain the recipes for a
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company’s proprietary or value-add software.
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Or, the package group could contain the recipes that enable
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graphics.
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A package group is really just another recipe.
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Because package group files are recipes, they end with the
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<filename>.bb</filename> filename extension.
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</para></listitem>
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<listitem><para id='poky'>
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<emphasis>Poky:</emphasis>
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The term "poky", which is pronounced
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<emphasis>Pah</emphasis>-kee, can mean several things:
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<itemizedlist>
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<listitem><para>
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In its most general sense, poky is an open-source
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project that was initially developed by OpenedHand.
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OpenedHand developed poky off of the existing
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OpenEmbedded build system to create a commercially
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supportable build system for embedded Linux.
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After Intel Corporation acquired OpenedHand, the
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poky project became the basis for the Yocto Project's
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build system.
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</para></listitem>
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<listitem><para>
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Within the Yocto Project
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<ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink>,
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"poky" exists as a separate Git
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repository from which you can clone to yield a local
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Git repository that is a copy on your host system.
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Thus, "poky" can refer to the upstream or
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local copy of the files used for development within
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the Yocto Project.
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</para></listitem>
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<listitem><para>
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Finally, "poky" can refer to the default
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<link linkend='var-DISTRO'><filename>DISTRO</filename></link>
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(i.e. distribution) created when you use the Yocto
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Project in conjunction with the
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<filename>poky</filename> repository to build an image.
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</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para>
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<emphasis>Recipe:</emphasis>
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A set of instructions for building packages.
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A recipe describes where you get source code, which patches
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to apply, how to configure the source, how to compile it and so on.
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Recipes also describe dependencies for libraries or for other
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recipes.
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Recipes represent the logical unit of execution, the software
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to build, the images to build, and use the
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<filename>.bb</filename> file extension.
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</para></listitem>
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<listitem><para id='reference-kit-term'>
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<emphasis>Reference Kit:</emphasis>
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A working example of a system, which includes a
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<link linkend='board-support-package-bsp-term'>BSP</link>
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as well as a
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<link linkend='hardware-build-system-term'>build system</link>
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and other components, that can work on specific hardware.
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</para></listitem>
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<listitem>
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<para id='source-directory'>
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<emphasis>Source Directory:</emphasis>
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This term refers to the directory structure created as a result
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of creating a local copy of the <filename>poky</filename> Git
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repository <filename>git://git.yoctoproject.org/poky</filename>
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or expanding a released <filename>poky</filename> tarball.
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<note>
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Creating a local copy of the <filename>poky</filename>
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Git repository is the recommended method for setting up
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your Source Directory.
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</note>
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Sometimes you might hear the term "poky directory" used to refer
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to this directory structure.
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<note>
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The OpenEmbedded build system does not support file or
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directory names that contain spaces.
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Be sure that the Source Directory you use does not contain
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these types of names.
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</note></para>
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<para>The Source Directory contains BitBake, Documentation,
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Metadata and other files that all support the Yocto Project.
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Consequently, you must have the Source Directory in place on
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your development system in order to do any development using
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the Yocto Project.</para>
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<para>When you create a local copy of the Git repository, you
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can name the repository anything you like.
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Throughout much of the documentation, "poky"
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is used as the name of the top-level folder of the local copy of
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the poky Git repository.
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So, for example, cloning the <filename>poky</filename> Git
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repository results in a local Git repository whose top-level
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folder is also named "poky".</para>
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<para>While it is not recommended that you use tarball expansion
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to set up the Source Directory, if you do, the top-level
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directory name of the Source Directory is derived from the
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Yocto Project release tarball.
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For example, downloading and unpacking
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<filename>&YOCTO_POKY_TARBALL;</filename> results in a
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Source Directory whose root folder is named
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<filename>&YOCTO_POKY;</filename>.</para>
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<para>It is important to understand the differences between the
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Source Directory created by unpacking a released tarball as
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compared to cloning
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<filename>git://git.yoctoproject.org/poky</filename>.
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When you unpack a tarball, you have an exact copy of the files
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based on the time of release - a fixed release point.
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Any changes you make to your local files in the Source Directory
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are on top of the release and will remain local only.
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On the other hand, when you clone the <filename>poky</filename>
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Git repository, you have an active development repository with
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access to the upstream repository's branches and tags.
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In this case, any local changes you make to the local
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Source Directory can be later applied to active development
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branches of the upstream <filename>poky</filename> Git
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repository.</para>
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<para>For more information on concepts related to Git
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repositories, branches, and tags, see the
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"<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#repositories-tags-and-branches'>Repositories, Tags, and Branches</ulink>"
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section in the Yocto Project Overview Manual.
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</para></listitem>
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<listitem><para><emphasis>Task:</emphasis>
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A unit of execution for BitBake (e.g.
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<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>,
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<link linkend='ref-tasks-fetch'><filename>do_fetch</filename></link>,
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<link linkend='ref-tasks-patch'><filename>do_patch</filename></link>,
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and so forth).
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</para></listitem>
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<listitem><para id='toaster-term'><emphasis>Toaster:</emphasis>
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A web interface to the Yocto Project's
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<link linkend='build-system-term'>OpenEmbedded Build System</link>.
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The interface enables you to configure and run your builds.
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Information about builds is collected and stored in a database.
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For information on Toaster, see the
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<ulink url='&YOCTO_DOCS_TOAST_URL;'>Yocto Project Toaster Manual</ulink>.
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</para></listitem>
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<listitem><para>
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<emphasis>Upstream:</emphasis>
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A reference to source code or repositories
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that are not local to the development system but located in a
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master area that is controlled by the maintainer of the source
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code.
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For example, in order for a developer to work on a particular
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||
piece of code, they need to first get a copy of it from an
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"upstream" source.
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</para></listitem>
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||
</itemizedlist>
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||
</para>
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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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