mirror of
https://git.yoctoproject.org/poky
synced 2026-04-19 06:32:13 +02:00
ref-manual: Re-organized the "Introduction" Chapter
I made some changes to better introduce this reference manual. Clarified the best scenario for using the manual. Removed the long list of manual descriptions as that can be referenced further down in the manual. (From yocto-docs rev: 8f4555aa387ab3bd3f90f5fcda1d343811ecc168) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
committed by
Richard Purdie
Richard Purdie
parent
800ee0167a
commit
3f6a9af927
@@ -5,10 +5,11 @@
|
||||
<chapter id='ref-manual-intro'>
|
||||
<title>Introduction</title>
|
||||
|
||||
<section id='intro-welcome'>
|
||||
<title>Introduction</title>
|
||||
<section id='ref-welcome'>
|
||||
<title>Welcome</title>
|
||||
|
||||
<para>
|
||||
Welcome to the Yocto Project Reference Manual.
|
||||
This manual provides reference information for the current release
|
||||
of the Yocto Project.
|
||||
The Yocto Project is an open-source collaboration project focused
|
||||
@@ -16,419 +17,37 @@
|
||||
Amongst other things, the Yocto Project uses the OpenEmbedded build
|
||||
system, which is based on the Poky project, to construct complete
|
||||
Linux images.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
This reference manual is best used after you have an understanding
|
||||
of the basics of the Yocto Project.
|
||||
The manual is not meant to be read as a starting point to the
|
||||
Yocto Project.
|
||||
Use this manual to find concepts, variable definitions, class
|
||||
descriptions, and so forth.
|
||||
The manual augments working with the Yocto Project during application
|
||||
and kernel development.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The Yocto Project Reference Manual does not provide "how-to",
|
||||
task-oriented information.
|
||||
You can find complete introductory and getting started information
|
||||
on the Yocto Project by reading the
|
||||
<ulink url='&YOCTO_DOCS_QS_URL;'>Yocto Project Quick Start</ulink>.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
For task-based information using the Yocto Project, see the
|
||||
<ulink url='&YOCTO_DOCS_DEV_URL;'>Yocto Project Development Manual</ulink>
|
||||
and the <ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;'>Yocto Project Linux Kernel Development Manual</ulink>.
|
||||
For Board Support Package (BSP) structure information, see the
|
||||
<ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
|
||||
For information on how to use a Software Development Kit, (SDK), see the
|
||||
<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>.
|
||||
You can find information on tracing and profiling in the
|
||||
<ulink url='&YOCTO_DOCS_PROF_URL;'>Yocto Project Profiling and Tracing Manual</ulink>.
|
||||
For information on BitBake, which is the task execution tool the
|
||||
OpenEmbedded build system is based on, see the
|
||||
<ulink url='&YOCTO_DOCS_BB_URL;#bitbake-user-manual'>BitBake User Manual</ulink>.
|
||||
Finally, you can also find lots of Yocto Project information on the
|
||||
<ulink url="&YOCTO_HOME_URL;">Yocto Project website</ulink>.
|
||||
</para>
|
||||
</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</ulink>"
|
||||
section in the Yocto Project Development 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='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>
|
||||
or
|
||||
<link linkend='structure-memres-core-script'><filename>oe-init-build-env-memres</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>
|
||||
<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 Software Development Kit (SDK) Developer's Guide</ulink>.
|
||||
</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"),
|
||||
it refers to Metadata in the <filename>meta</filename>
|
||||
branches of the kernel source Git repositories.
|
||||
</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" can mean several things.
|
||||
In its most general sense, it is an open-source
|
||||
project that was initially developed by OpenedHand.
|
||||
With OpenedHand, poky was developed off of the existing
|
||||
OpenEmbedded build system becoming a commercially
|
||||
supportable build system for embedded Linux.
|
||||
After Intel Corporation acquired OpenedHand, the
|
||||
project poky became the basis for the Yocto Project's
|
||||
build system.</para>
|
||||
|
||||
<para>Within the Yocto Project source repositories,
|
||||
<filename>poky</filename> exists as a separate Git
|
||||
repository you can clone to yield a local copy on your
|
||||
host system.
|
||||
Thus, "poky" can refer to the local copy of the Source
|
||||
Directory used for development within the Yocto
|
||||
Project.</para>
|
||||
|
||||
<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>
|
||||
<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='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_DEV_URL;#repositories-tags-and-branches'>Repositories, Tags, and Branches</ulink>"
|
||||
section in the Yocto Project Development 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>
|
||||
<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>
|
||||
You can find "how-to" information in the
|
||||
<ulink url='&YOCTO_DOCS_DEV_URL;'>Yocto Project Development Manual</ulink>.
|
||||
<note><title>Tip</title>
|
||||
For more information about the Yocto Project Documentation set,
|
||||
see the
|
||||
"<link linkend='resources-links-and-related-documentation'>Links and Related Documentation</link>"
|
||||
section.
|
||||
</note>
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<!--
|
||||
<section id='intro-manualoverview'>
|
||||
<title>Documentation Overview</title>
|
||||
<para>
|
||||
@@ -545,7 +164,7 @@
|
||||
</itemizedlist>
|
||||
</para>
|
||||
</section>
|
||||
|
||||
-->
|
||||
|
||||
<section id='intro-requirements'>
|
||||
<title>System Requirements</title>
|
||||
@@ -1050,6 +669,396 @@
|
||||
</para>
|
||||
</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</ulink>"
|
||||
section in the Yocto Project Development 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='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>
|
||||
or
|
||||
<link linkend='structure-memres-core-script'><filename>oe-init-build-env-memres</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>
|
||||
<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 Software Development Kit (SDK) Developer's Guide</ulink>.
|
||||
</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"),
|
||||
it refers to Metadata in the <filename>meta</filename>
|
||||
branches of the kernel source Git repositories.
|
||||
</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" can mean several things.
|
||||
In its most general sense, it is an open-source
|
||||
project that was initially developed by OpenedHand.
|
||||
With OpenedHand, poky was developed off of the existing
|
||||
OpenEmbedded build system becoming a commercially
|
||||
supportable build system for embedded Linux.
|
||||
After Intel Corporation acquired OpenedHand, the
|
||||
project poky became the basis for the Yocto Project's
|
||||
build system.</para>
|
||||
|
||||
<para>Within the Yocto Project source repositories,
|
||||
<filename>poky</filename> exists as a separate Git
|
||||
repository you can clone to yield a local copy on your
|
||||
host system.
|
||||
Thus, "poky" can refer to the local copy of the Source
|
||||
Directory used for development within the Yocto
|
||||
Project.</para>
|
||||
|
||||
<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>
|
||||
<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='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_DEV_URL;#repositories-tags-and-branches'>Repositories, Tags, and Branches</ulink>"
|
||||
section in the Yocto Project Development 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>
|
||||
<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>
|
||||
<!--
|
||||
vim: expandtab tw=80 ts=4
|
||||
|
||||
Reference in New Issue
Block a user