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ref-manual: Separated terms into separate chapter

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Pulling out some introductory information from the old "Introduction"
chapter of the ref-manual has isolated the system requirements and
term definitions sections.  I have decided to create a new chapter
for terms as they are a reference item.  This leaves system requirements
also alone as a new chapter.  So, I dumped the introduction.xml chapter
in favor of the two new chapters.

(From yocto-docs rev: 35c41b3008845c94e10be19b37409b0d1a469ff5)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2018-01-05 15:43:42 -08:00
committed by Richard Purdie
parent c06a654c1d
commit 60cfd0785b
4 changed files with 448 additions and 452 deletions
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documentation/mega-manual/mega-manual.xml
+4 -1
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@@ -231,7 +231,10 @@
</para> </para>
<xi:include <xi:include
xmlns:xi="http://www.w3.org/2003/XInclude" href="../ref-manual/introduction.xml"/> xmlns:xi="http://www.w3.org/2003/XInclude" href="../ref-manual/ref-system-requirements.xml"/>
<xi:include
xmlns:xi="http://www.w3.org/2003/XInclude" href="../ref-manual/ref-terms.xml"/>
<xi:include <xi:include
xmlns:xi="http://www.w3.org/2003/XInclude" href="../ref-manual/usingpoky.xml"/> xmlns:xi="http://www.w3.org/2003/XInclude" href="../ref-manual/usingpoky.xml"/>
documentation/ref-manual/ref-manual.xml
+3 -1
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@@ -166,7 +166,9 @@
</bookinfo> </bookinfo>
<xi:include href="introduction.xml"/> <xi:include href="ref-system-requirements.xml"/>
<xi:include href="ref-terms.xml"/>
<xi:include href="usingpoky.xml"/> <xi:include href="usingpoky.xml"/>
documentation/ref-manual/introduction.xml → documentation/ref-manual/ref-system-requirements.xml
+5 -450
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@@ -2,21 +2,18 @@
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
<chapter id='ref-manual-intro'> <chapter id='ref-manual-system-requirements'>
<title>Introduction</title> <title>System Requirements</title>
<section id='ref-welcome'>
<title>Welcome</title>
<para> <para>
Welcome to the Yocto Project Reference Manual. Welcome to the Yocto Project Reference Manual!
This manual provides reference information for the current release This manual provides reference information for the current release
of the Yocto Project. of the Yocto Project.
This manual is best used after you have an understanding The manual is best used after you have an understanding
of the basics of the Yocto Project. of the basics of the Yocto Project.
The manual is neither meant to be read as a starting point to the The manual is neither meant to be read as a starting point to the
Yocto Project nor read from start to finish. Yocto Project nor read from start to finish.
Use this manual to find concepts, variable definitions, class Use this manual to find variable definitions, class
descriptions, and so forth as needed during the course of using descriptions, and so forth as needed during the course of using
the Yocto Project. the Yocto Project.
</para> </para>
@@ -41,17 +38,6 @@
section. section.
</note> </note>
</para> </para>
</section>
<section id='intro-requirements'>
<title>System Requirements</title>
<para>
For general Yocto Project system requirements, see the
"<ulink url='&YOCTO_DOCS_QS_URL;#yp-resources'>Setting Up to Use the Yocto Project</ulink>" section
in the Yocto Project Quick Start.
The remainder of this section provides details on system requirements
not covered in the Yocto Project Quick Start.
</para>
<section id='detailed-supported-distros'> <section id='detailed-supported-distros'>
<title>Supported Linux Distributions</title> <title>Supported Linux Distributions</title>
@@ -500,437 +486,6 @@
</para> </para>
</section> </section>
</section> </section>
</section>
<section id='yocto-project-terms'>
<title>Yocto Project Terms</title>
<para>
Following is a list of terms and definitions users new to the Yocto
Project development environment might find helpful.
While some of these terms are universal, the list includes them
just in case:
<itemizedlist>
<listitem><para>
<emphasis>Append Files:</emphasis>
Files that append build information to a recipe file.
Append files are known as BitBake append files and
<filename>.bbappend</filename> files.
The OpenEmbedded build system expects every append file to have
a corresponding recipe (<filename>.bb</filename>) 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 extends or overrides the
information in the similarly-named recipe file.
For an example of an append file in use, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
section in the Yocto Project Development Tasks Manual.
<note>
Append files can also use wildcard patterns in their
version numbers so they can be applied to more than one
version of the underlying recipe file.
</note>
</para></listitem>
<listitem><para id='bitbake-term'>
<emphasis>BitBake:</emphasis>
The task executor and scheduler used by the OpenEmbedded build
system to build images.
For more information on BitBake, see the
<ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
</para></listitem>
<listitem><para id='board-support-package-bsp-term'>
<emphasis>Board Support Package (BSP):</emphasis>
A group of drivers, definitions, and other components that
provide support for a specific hardware configuration.
For more information on BSPs, see the
<ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
</para></listitem>
<listitem>
<para id='build-directory'>
<emphasis>Build Directory:</emphasis>
This term refers to the area used by the OpenEmbedded build
system for builds.
The area is created when you <filename>source</filename> the
setup environment script that is found in the Source Directory
(i.e. <link linkend='structure-core-script'><filename>&OE_INIT_FILE;</filename></link>).
The
<link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
variable points to the Build Directory.</para>
<para>You have a lot of flexibility when creating the Build
Directory.
Following are some examples that show how to create the
directory.
The examples assume your
<link linkend='source-directory'>Source Directory</link> is
named <filename>poky</filename>:
<itemizedlist>
<listitem><para>Create the Build Directory inside your
Source Directory and let the name of the Build
Directory default to <filename>build</filename>:
<literallayout class='monospaced'>
$ cd $HOME/poky
$ source &OE_INIT_FILE;
</literallayout>
</para></listitem>
<listitem><para>Create the Build Directory inside your
home directory and specifically name it
<filename>test-builds</filename>:
<literallayout class='monospaced'>
$ cd $HOME
$ source poky/&OE_INIT_FILE; test-builds
</literallayout>
</para></listitem>
<listitem><para>
Provide a directory path and specifically name the
Build Directory.
Any intermediate folders in the pathname must exist.
This next example creates a Build Directory named
<filename>YP-&POKYVERSION;</filename>
in your home directory within the existing
directory <filename>mybuilds</filename>:
<literallayout class='monospaced'>
$cd $HOME
$ source $HOME/poky/&OE_INIT_FILE; $HOME/mybuilds/YP-&POKYVERSION;
</literallayout>
</para></listitem>
</itemizedlist>
<note>
By default, the Build Directory contains
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>,
which is a temporary directory the build system uses for
its work.
<filename>TMPDIR</filename> cannot be under NFS.
Thus, by default, the Build Directory cannot be under NFS.
However, if you need the Build Directory to be under NFS,
you can set this up by setting <filename>TMPDIR</filename>
in your <filename>local.conf</filename> file
to use a local drive.
Doing so effectively separates <filename>TMPDIR</filename>
from <filename>TOPDIR</filename>, which is the Build
Directory.
</note>
</para></listitem>
<listitem><para id='hardware-build-system-term'>
<emphasis>Build System:</emphasis>
The system used to build images in a Yocto Project
Development environment.
The build system is sometimes referred to as the
development host.
</para></listitem>
<listitem><para>
<emphasis>Classes:</emphasis>
Files that provide for logic encapsulation and inheritance so
that commonly used patterns can be defined once and then
easily used in multiple recipes.
For reference information on the Yocto Project classes, see the
"<link linkend='ref-classes'>Classes</link>" chapter.
Class files end with the <filename>.bbclass</filename>
filename extension.
</para></listitem>
<listitem><para>
<emphasis>Configuration File:</emphasis>
Configuration information in various <filename>.conf</filename>
files provides global definitions of variables.
The <filename>conf/local.conf</filename> configuration file in
the
<link linkend='build-directory'>Build Directory</link>
contains user-defined variables that affect every build.
The <filename>meta-poky/conf/distro/poky.conf</filename>
configuration file defines Yocto "distro" configuration
variables used only when building with this policy.
Machine configuration files, which
are located throughout the
<link linkend='source-directory'>Source Directory</link>, define
variables for specific hardware and are only used when building
for that target (e.g. the
<filename>machine/beaglebone.conf</filename> configuration
file defines variables for the Texas Instruments ARM Cortex-A8
development board).
Configuration files end with a <filename>.conf</filename>
filename extension.
</para></listitem>
<listitem><para id='cross-development-toolchain'>
<emphasis>Cross-Development Toolchain:</emphasis>
In general, a cross-development toolchain is a collection of
software development tools and utilities that run on one
architecture and allow you to develop software for a
different, or targeted, architecture.
These toolchains contain cross-compilers, linkers, and
debuggers that are specific to the target architecture.</para>
<para>The Yocto Project supports two different cross-development
toolchains:
<itemizedlist>
<listitem><para>
A toolchain only used by and within
BitBake when building an image for a target
architecture.
</para></listitem>
<listitem><para>A relocatable toolchain used outside of
BitBake by developers when developing applications
that will run on a targeted device.
</para></listitem>
</itemizedlist></para>
<para>Creation of these toolchains is simple and automated.
For information on toolchain concepts as they apply to the
Yocto Project, see the
"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
section.
You can also find more information on using the
relocatable toolchain in the
<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Application Development and the Extensible Software Development Kit (eSDK)</ulink>
manual.
</para></listitem>
<listitem><para>
<emphasis>Image:</emphasis>
An image is an artifact of the BitBake build process given
a collection of recipes and related Metadata.
Images are the binary output that run on specific hardware or
QEMU and are used for specific use-cases.
For a list of the supported image types that the Yocto Project
provides, see the
"<link linkend='ref-images'>Images</link>"
chapter.
</para></listitem>
<listitem><para>
<emphasis>Layer:</emphasis>
A collection of recipes representing the core,
a BSP, or an application stack.
For a discussion specifically on BSP Layers, see the
"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
section in the Yocto Project Board Support Packages (BSP)
Developer's Guide.
</para></listitem>
<listitem><para id='metadata'>
<emphasis>Metadata:</emphasis>
The files that BitBake parses when building an image.
In general, Metadata includes recipes, classes, and
configuration files.
In the context of the kernel ("kernel Metadata"), the
term refers to the kernel config fragments and features
contained in the
<ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache'><filename>yocto-kernel-cache</filename></ulink>
Git repository.
</para></listitem>
<listitem><para id='oe-core'>
<emphasis>OE-Core:</emphasis>
A core set of Metadata originating with OpenEmbedded (OE)
that is shared between OE and the Yocto Project.
This Metadata is found in the <filename>meta</filename>
directory of the
<link linkend='source-directory'>Source Directory</link>.
</para></listitem>
<listitem><para id='build-system-term'>
<emphasis>OpenEmbedded Build System:</emphasis>
The build system specific to the Yocto Project.
The OpenEmbedded build system is based on another project known
as "Poky", which uses
<link linkend='bitbake-term'>BitBake</link> as the task
executor.
Throughout the Yocto Project documentation set, the
OpenEmbedded build system is sometimes referred to simply
as "the build system".
If other build systems, such as a host or target build system
are referenced, the documentation clearly states the
difference.
<note>
For some historical information about Poky, see the
<link linkend='poky'>Poky</link> term.
</note>
</para></listitem>
<listitem><para>
<emphasis>Package:</emphasis>
In the context of the Yocto Project, this term refers to a
recipe's packaged output produced by BitBake (i.e. a
"baked recipe").
A package is generally the compiled binaries produced from the
recipe's sources.
You "bake" something by running it through BitBake.</para>
<para>It is worth noting that the term "package" can,
in general, have subtle meanings.
For example, the packages referred to in the
"<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>"
section in the Yocto Project Quick Start are compiled binaries
that, when installed, add functionality to your Linux
distribution.</para>
<para>Another point worth noting is that historically within
the Yocto Project, recipes were referred to as packages - thus,
the existence of several BitBake variables that are seemingly
mis-named,
(e.g. <link linkend='var-PR'><filename>PR</filename></link>,
<link linkend='var-PV'><filename>PV</filename></link>, and
<link linkend='var-PE'><filename>PE</filename></link>).
</para></listitem>
<listitem><para>
<emphasis>Package Groups:</emphasis>
Arbitrary groups of software Recipes.
You use package groups to hold recipes that, when built,
usually accomplish a single task.
For example, a package group could contain the recipes for a
company’s proprietary or value-add software.
Or, the package group could contain the recipes that enable
graphics.
A package group is really just another recipe.
Because package group files are recipes, they end with the
<filename>.bb</filename> filename extension.
</para></listitem>
<listitem><para id='poky'>
<emphasis>Poky:</emphasis>
The term "poky", which is pronounced
<emphasis>Pah</emphasis>-kee, can mean several things:
<itemizedlist>
<listitem><para>
In its most general sense, poky is an open-source
project that was initially developed by OpenedHand.
OpenedHand developed poky off of the existing
OpenEmbedded build system to create a commercially
supportable build system for embedded Linux.
After Intel Corporation acquired OpenedHand, the
poky project became the basis for the Yocto Project's
build system.
</para></listitem>
<listitem><para>
Within the Yocto Project
<ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink>,
"poky" exists as a separate Git
repository from which you can clone to yield a local
Git repository that is a copy on your host system.
Thus, "poky" can refer to the upstream or
local copy of the files used for development within
the Yocto Project.
</para></listitem>
<listitem><para>
Finally, "poky" can refer to the default
<link linkend='var-DISTRO'><filename>DISTRO</filename></link>
(i.e. distribution) created when you use the Yocto
Project in conjunction with the
<filename>poky</filename> repository to build an image.
</para></listitem>
</itemizedlist>
</para></listitem>
<listitem><para>
<emphasis>Recipe:</emphasis>
A set of instructions for building packages.
A recipe describes where you get source code, which patches
to apply, how to configure the source, how to compile it and so on.
Recipes also describe dependencies for libraries or for other
recipes.
Recipes represent the logical unit of execution, the software
to build, the images to build, and use the
<filename>.bb</filename> file extension.
</para></listitem>
<listitem><para id='reference-kit-term'>
<emphasis>Reference Kit:</emphasis>
A working example of a system, which includes a
<link linkend='board-support-package-bsp-term'>BSP</link>
as well as a
<link linkend='hardware-build-system-term'>build system</link>
and other components, that can work on specific hardware.
</para></listitem>
<listitem>
<para id='source-directory'>
<emphasis>Source Directory:</emphasis>
This term refers to the directory structure created as a result
of creating a local copy of the <filename>poky</filename> Git
repository <filename>git://git.yoctoproject.org/poky</filename>
or expanding a released <filename>poky</filename> tarball.
<note>
Creating a local copy of the <filename>poky</filename>
Git repository is the recommended method for setting up
your Source Directory.
</note>
Sometimes you might hear the term "poky directory" used to refer
to this directory structure.
<note>
The OpenEmbedded build system does not support file or
directory names that contain spaces.
Be sure that the Source Directory you use does not contain
these types of names.
</note></para>
<para>The Source Directory contains BitBake, Documentation,
Metadata and other files that all support the Yocto Project.
Consequently, you must have the Source Directory in place on
your development system in order to do any development using
the Yocto Project.</para>
<para>When you create a local copy of the Git repository, you
can name the repository anything you like.
Throughout much of the documentation, "poky"
is used as the name of the top-level folder of the local copy of
the poky Git repository.
So, for example, cloning the <filename>poky</filename> Git
repository results in a local Git repository whose top-level
folder is also named "poky".</para>
<para>While it is not recommended that you use tarball expansion
to set up the Source Directory, if you do, the top-level
directory name of the Source Directory is derived from the
Yocto Project release tarball.
For example, downloading and unpacking
<filename>&YOCTO_POKY_TARBALL;</filename> results in a
Source Directory whose root folder is named
<filename>&YOCTO_POKY;</filename>.</para>
<para>It is important to understand the differences between the
Source Directory created by unpacking a released tarball as
compared to cloning
<filename>git://git.yoctoproject.org/poky</filename>.
When you unpack a tarball, you have an exact copy of the files
based on the time of release - a fixed release point.
Any changes you make to your local files in the Source Directory
are on top of the release and will remain local only.
On the other hand, when you clone the <filename>poky</filename>
Git repository, you have an active development repository with
access to the upstream repository's branches and tags.
In this case, any local changes you make to the local
Source Directory can be later applied to active development
branches of the upstream <filename>poky</filename> Git
repository.</para>
<para>For more information on concepts related to Git
repositories, branches, and tags, see the
"<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#repositories-tags-and-branches'>Repositories, Tags, and Branches</ulink>"
section in the Yocto Project Overview Manual.
</para></listitem>
<listitem><para><emphasis>Task:</emphasis>
A unit of execution for BitBake (e.g.
<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>,
<link linkend='ref-tasks-fetch'><filename>do_fetch</filename></link>,
<link linkend='ref-tasks-patch'><filename>do_patch</filename></link>,
and so forth).
</para></listitem>
<listitem><para id='toaster-term'><emphasis>Toaster:</emphasis>
A web interface to the Yocto Project's
<link linkend='build-system-term'>OpenEmbedded Build System</link>.
The interface enables you to configure and run your builds.
Information about builds is collected and stored in a database.
For information on Toaster, see the
<ulink url='&YOCTO_DOCS_TOAST_URL;'>Yocto Project Toaster Manual</ulink>.
</para></listitem>
<listitem><para>
<emphasis>Upstream:</emphasis>
A reference to source code or repositories
that are not local to the development system but located in a
master area that is controlled by the maintainer of the source
code.
For example, in order for a developer to work on a particular
piece of code, they need to first get a copy of it from an
"upstream" source.
</para></listitem>
</itemizedlist>
</para>
</section>
</chapter> </chapter>
<!-- <!--
vim: expandtab tw=80 ts=4 vim: expandtab tw=80 ts=4
documentation/ref-manual/ref-terms.xml
+436
View File
@@ -0,0 +1,436 @@
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
<chapter id='ref-terms'>
<title>Yocto Project Terms</title>
<para>
Following is a list of terms and definitions users new to the Yocto
Project development environment might find helpful.
While some of these terms are universal, the list includes them
just in case:
<itemizedlist>
<listitem><para>
<emphasis>Append Files:</emphasis>
Files that append build information to a recipe file.
Append files are known as BitBake append files and
<filename>.bbappend</filename> files.
The OpenEmbedded build system expects every append file to have
a corresponding recipe (<filename>.bb</filename>) 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 extends or overrides the
information in the similarly-named recipe file.
For an example of an append file in use, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
section in the Yocto Project Development Tasks Manual.
<note>
Append files can also use wildcard patterns in their
version numbers so they can be applied to more than one
version of the underlying recipe file.
</note>
</para></listitem>
<listitem><para id='bitbake-term'>
<emphasis>BitBake:</emphasis>
The task executor and scheduler used by the OpenEmbedded build
system to build images.
For more information on BitBake, see the
<ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
</para></listitem>
<listitem><para id='board-support-package-bsp-term'>
<emphasis>Board Support Package (BSP):</emphasis>
A group of drivers, definitions, and other components that
provide support for a specific hardware configuration.
For more information on BSPs, see the
<ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
</para></listitem>
<listitem>
<para id='build-directory'>
<emphasis>Build Directory:</emphasis>
This term refers to the area used by the OpenEmbedded build
system for builds.
The area is created when you <filename>source</filename> the
setup environment script that is found in the Source Directory
(i.e. <link linkend='structure-core-script'><filename>&OE_INIT_FILE;</filename></link>).
The
<link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
variable points to the Build Directory.</para>
<para>You have a lot of flexibility when creating the Build
Directory.
Following are some examples that show how to create the
directory.
The examples assume your
<link linkend='source-directory'>Source Directory</link> is
named <filename>poky</filename>:
<itemizedlist>
<listitem><para>Create the Build Directory inside your
Source Directory and let the name of the Build
Directory default to <filename>build</filename>:
<literallayout class='monospaced'>
$ cd $HOME/poky
$ source &OE_INIT_FILE;
</literallayout>
</para></listitem>
<listitem><para>Create the Build Directory inside your
home directory and specifically name it
<filename>test-builds</filename>:
<literallayout class='monospaced'>
$ cd $HOME
$ source poky/&OE_INIT_FILE; test-builds
</literallayout>
</para></listitem>
<listitem><para>
Provide a directory path and specifically name the
Build Directory.
Any intermediate folders in the pathname must exist.
This next example creates a Build Directory named
<filename>YP-&POKYVERSION;</filename>
in your home directory within the existing
directory <filename>mybuilds</filename>:
<literallayout class='monospaced'>
$cd $HOME
$ source $HOME/poky/&OE_INIT_FILE; $HOME/mybuilds/YP-&POKYVERSION;
</literallayout>
</para></listitem>
</itemizedlist>
<note>
By default, the Build Directory contains
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>,
which is a temporary directory the build system uses for
its work.
<filename>TMPDIR</filename> cannot be under NFS.
Thus, by default, the Build Directory cannot be under NFS.
However, if you need the Build Directory to be under NFS,
you can set this up by setting <filename>TMPDIR</filename>
in your <filename>local.conf</filename> file
to use a local drive.
Doing so effectively separates <filename>TMPDIR</filename>
from <filename>TOPDIR</filename>, which is the Build
Directory.
</note>
</para></listitem>
<listitem><para id='hardware-build-system-term'>
<emphasis>Build System:</emphasis>
The system used to build images in a Yocto Project
Development environment.
The build system is sometimes referred to as the
development host.
</para></listitem>
<listitem><para>
<emphasis>Classes:</emphasis>
Files that provide for logic encapsulation and inheritance so
that commonly used patterns can be defined once and then
easily used in multiple recipes.
For reference information on the Yocto Project classes, see the
"<link linkend='ref-classes'>Classes</link>" chapter.
Class files end with the <filename>.bbclass</filename>
filename extension.
</para></listitem>
<listitem><para>
<emphasis>Configuration File:</emphasis>
Configuration information in various <filename>.conf</filename>
files provides global definitions of variables.
The <filename>conf/local.conf</filename> configuration file in
the
<link linkend='build-directory'>Build Directory</link>
contains user-defined variables that affect every build.
The <filename>meta-poky/conf/distro/poky.conf</filename>
configuration file defines Yocto "distro" configuration
variables used only when building with this policy.
Machine configuration files, which
are located throughout the
<link linkend='source-directory'>Source Directory</link>, define
variables for specific hardware and are only used when building
for that target (e.g. the
<filename>machine/beaglebone.conf</filename> configuration
file defines variables for the Texas Instruments ARM Cortex-A8
development board).
Configuration files end with a <filename>.conf</filename>
filename extension.
</para></listitem>
<listitem><para id='cross-development-toolchain'>
<emphasis>Cross-Development Toolchain:</emphasis>
In general, a cross-development toolchain is a collection of
software development tools and utilities that run on one
architecture and allow you to develop software for a
different, or targeted, architecture.
These toolchains contain cross-compilers, linkers, and
debuggers that are specific to the target architecture.</para>
<para>The Yocto Project supports two different cross-development
toolchains:
<itemizedlist>
<listitem><para>
A toolchain only used by and within
BitBake when building an image for a target
architecture.
</para></listitem>
<listitem><para>A relocatable toolchain used outside of
BitBake by developers when developing applications
that will run on a targeted device.
</para></listitem>
</itemizedlist></para>
<para>Creation of these toolchains is simple and automated.
For information on toolchain concepts as they apply to the
Yocto Project, see the
"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
section.
You can also find more information on using the
relocatable toolchain in the
<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Application Development and the Extensible Software Development Kit (eSDK)</ulink>
manual.
</para></listitem>
<listitem><para>
<emphasis>Image:</emphasis>
An image is an artifact of the BitBake build process given
a collection of recipes and related Metadata.
Images are the binary output that run on specific hardware or
QEMU and are used for specific use-cases.
For a list of the supported image types that the Yocto Project
provides, see the
"<link linkend='ref-images'>Images</link>"
chapter.
</para></listitem>
<listitem><para>
<emphasis>Layer:</emphasis>
A collection of recipes representing the core,
a BSP, or an application stack.
For a discussion specifically on BSP Layers, see the
"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
section in the Yocto Project Board Support Packages (BSP)
Developer's Guide.
</para></listitem>
<listitem><para id='metadata'>
<emphasis>Metadata:</emphasis>
The files that BitBake parses when building an image.
In general, Metadata includes recipes, classes, and
configuration files.
In the context of the kernel ("kernel Metadata"), the
term refers to the kernel config fragments and features
contained in the
<ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache'><filename>yocto-kernel-cache</filename></ulink>
Git repository.
</para></listitem>
<listitem><para id='oe-core'>
<emphasis>OE-Core:</emphasis>
A core set of Metadata originating with OpenEmbedded (OE)
that is shared between OE and the Yocto Project.
This Metadata is found in the <filename>meta</filename>
directory of the
<link linkend='source-directory'>Source Directory</link>.
</para></listitem>
<listitem><para id='build-system-term'>
<emphasis>OpenEmbedded Build System:</emphasis>
The build system specific to the Yocto Project.
The OpenEmbedded build system is based on another project known
as "Poky", which uses
<link linkend='bitbake-term'>BitBake</link> as the task
executor.
Throughout the Yocto Project documentation set, the
OpenEmbedded build system is sometimes referred to simply
as "the build system".
If other build systems, such as a host or target build system
are referenced, the documentation clearly states the
difference.
<note>
For some historical information about Poky, see the
<link linkend='poky'>Poky</link> term.
</note>
</para></listitem>
<listitem><para>
<emphasis>Package:</emphasis>
In the context of the Yocto Project, this term refers to a
recipe's packaged output produced by BitBake (i.e. a
"baked recipe").
A package is generally the compiled binaries produced from the
recipe's sources.
You "bake" something by running it through BitBake.</para>
<para>It is worth noting that the term "package" can,
in general, have subtle meanings.
For example, the packages referred to in the
"<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>"
section in the Yocto Project Quick Start are compiled binaries
that, when installed, add functionality to your Linux
distribution.</para>
<para>Another point worth noting is that historically within
the Yocto Project, recipes were referred to as packages - thus,
the existence of several BitBake variables that are seemingly
mis-named,
(e.g. <link linkend='var-PR'><filename>PR</filename></link>,
<link linkend='var-PV'><filename>PV</filename></link>, and
<link linkend='var-PE'><filename>PE</filename></link>).
</para></listitem>
<listitem><para>
<emphasis>Package Groups:</emphasis>
Arbitrary groups of software Recipes.
You use package groups to hold recipes that, when built,
usually accomplish a single task.
For example, a package group could contain the recipes for a
company’s proprietary or value-add software.
Or, the package group could contain the recipes that enable
graphics.
A package group is really just another recipe.
Because package group files are recipes, they end with the
<filename>.bb</filename> filename extension.
</para></listitem>
<listitem><para id='poky'>
<emphasis>Poky:</emphasis>
The term "poky", which is pronounced
<emphasis>Pah</emphasis>-kee, can mean several things:
<itemizedlist>
<listitem><para>
In its most general sense, poky is an open-source
project that was initially developed by OpenedHand.
OpenedHand developed poky off of the existing
OpenEmbedded build system to create a commercially
supportable build system for embedded Linux.
After Intel Corporation acquired OpenedHand, the
poky project became the basis for the Yocto Project's
build system.
</para></listitem>
<listitem><para>
Within the Yocto Project
<ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink>,
"poky" exists as a separate Git
repository from which you can clone to yield a local
Git repository that is a copy on your host system.
Thus, "poky" can refer to the upstream or
local copy of the files used for development within
the Yocto Project.
</para></listitem>
<listitem><para>
Finally, "poky" can refer to the default
<link linkend='var-DISTRO'><filename>DISTRO</filename></link>
(i.e. distribution) created when you use the Yocto
Project in conjunction with the
<filename>poky</filename> repository to build an image.
</para></listitem>
</itemizedlist>
</para></listitem>
<listitem><para>
<emphasis>Recipe:</emphasis>
A set of instructions for building packages.
A recipe describes where you get source code, which patches
to apply, how to configure the source, how to compile it and so on.
Recipes also describe dependencies for libraries or for other
recipes.
Recipes represent the logical unit of execution, the software
to build, the images to build, and use the
<filename>.bb</filename> file extension.
</para></listitem>
<listitem><para id='reference-kit-term'>
<emphasis>Reference Kit:</emphasis>
A working example of a system, which includes a
<link linkend='board-support-package-bsp-term'>BSP</link>
as well as a
<link linkend='hardware-build-system-term'>build system</link>
and other components, that can work on specific hardware.
</para></listitem>
<listitem>
<para id='source-directory'>
<emphasis>Source Directory:</emphasis>
This term refers to the directory structure created as a result
of creating a local copy of the <filename>poky</filename> Git
repository <filename>git://git.yoctoproject.org/poky</filename>
or expanding a released <filename>poky</filename> tarball.
<note>
Creating a local copy of the <filename>poky</filename>
Git repository is the recommended method for setting up
your Source Directory.
</note>
Sometimes you might hear the term "poky directory" used to refer
to this directory structure.
<note>
The OpenEmbedded build system does not support file or
directory names that contain spaces.
Be sure that the Source Directory you use does not contain
these types of names.
</note></para>
<para>The Source Directory contains BitBake, Documentation,
Metadata and other files that all support the Yocto Project.
Consequently, you must have the Source Directory in place on
your development system in order to do any development using
the Yocto Project.</para>
<para>When you create a local copy of the Git repository, you
can name the repository anything you like.
Throughout much of the documentation, "poky"
is used as the name of the top-level folder of the local copy of
the poky Git repository.
So, for example, cloning the <filename>poky</filename> Git
repository results in a local Git repository whose top-level
folder is also named "poky".</para>
<para>While it is not recommended that you use tarball expansion
to set up the Source Directory, if you do, the top-level
directory name of the Source Directory is derived from the
Yocto Project release tarball.
For example, downloading and unpacking
<filename>&YOCTO_POKY_TARBALL;</filename> results in a
Source Directory whose root folder is named
<filename>&YOCTO_POKY;</filename>.</para>
<para>It is important to understand the differences between the
Source Directory created by unpacking a released tarball as
compared to cloning
<filename>git://git.yoctoproject.org/poky</filename>.
When you unpack a tarball, you have an exact copy of the files
based on the time of release - a fixed release point.
Any changes you make to your local files in the Source Directory
are on top of the release and will remain local only.
On the other hand, when you clone the <filename>poky</filename>
Git repository, you have an active development repository with
access to the upstream repository's branches and tags.
In this case, any local changes you make to the local
Source Directory can be later applied to active development
branches of the upstream <filename>poky</filename> Git
repository.</para>
<para>For more information on concepts related to Git
repositories, branches, and tags, see the
"<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#repositories-tags-and-branches'>Repositories, Tags, and Branches</ulink>"
section in the Yocto Project Overview Manual.
</para></listitem>
<listitem><para><emphasis>Task:</emphasis>
A unit of execution for BitBake (e.g.
<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>,
<link linkend='ref-tasks-fetch'><filename>do_fetch</filename></link>,
<link linkend='ref-tasks-patch'><filename>do_patch</filename></link>,
and so forth).
</para></listitem>
<listitem><para id='toaster-term'><emphasis>Toaster:</emphasis>
A web interface to the Yocto Project's
<link linkend='build-system-term'>OpenEmbedded Build System</link>.
The interface enables you to configure and run your builds.
Information about builds is collected and stored in a database.
For information on Toaster, see the
<ulink url='&YOCTO_DOCS_TOAST_URL;'>Yocto Project Toaster Manual</ulink>.
</para></listitem>
<listitem><para>
<emphasis>Upstream:</emphasis>
A reference to source code or repositories
that are not local to the development system but located in a
master area that is controlled by the maintainer of the source
code.
For example, in order for a developer to work on a particular
piece of code, they need to first get a copy of it from an
"upstream" source.
</para></listitem>
</itemizedlist>
</para>
</chapter>
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