cbcdc22d90
(From yocto-docs rev: 0f8b655da637ebf7708bdfff1473707c9ea3b8ef) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
818 lines
49 KiB
XML
818 lines
49 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<chapter id='dev-manual-newbie'>
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<title>The Yocto Project Open Source Development Environment</title>
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<para>
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This chapter helps you understand the Yocto Project as an open source development project.
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In general, working in an open source environment is very different as compared to working in a
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proprietary environment.
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Additionally, the Yocto Project uses specific tools and constructs as part of its development
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environment.
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The chapter specifically addresses open source philosophy, licensing issues, code repositories,
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the open source distributed version control system Git, and best practices using the Yocto Project.
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</para>
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<section id='open-source-philosophy'>
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<title>Open Source Philosophy</title>
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<para>
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Open source philosophy is characterized by software development directed by peer production
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and collaboration through a concerned community of developers.
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Contrast this to the more standard centralized development models used by commercial software
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companies where a finite set of developers produce a product for sale using a defined set
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of procedures that ultimately result in an end-product whose architecture and source material
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are closed to the public.
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</para>
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<para>
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Open source projects conceptually have differing concurrent agendas, approaches, and production.
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These facets of the development process can come from anyone in the public (community) that has a
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stake in the software project.
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The open source environment contains new copyright, licensing, domain, and consumer issues
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that differ from the more traditional development environment.
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In an open source environment, the end-product, source material, and documentation are
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all available to the public at no cost.
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</para>
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<para>
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A benchmark example of an open source project is the Linux Kernel, which was initially conceived
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and created by Finnish computer science student Linus Torvalds in 1991.
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Conversely, a good example of a non-open source project is the
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<trademark class='registered'>Windows</trademark> family of operating
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systems developed by <trademark class='registered'>Microsoft</trademark> Corporation.
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</para>
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<para>
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Wikipedia has a good historical description of the Open Source Philosophy
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<ulink url='http://en.wikipedia.org/wiki/Open_source'>here</ulink>.
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You can also find helpful information on how to participate in the Linux Community
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<ulink url='http://ldn.linuxfoundation.org/book/how-participate-linux-community'>here</ulink>.
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</para>
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</section>
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<section id='yocto-project-repositories'>
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<title>Yocto Project Source Repositories</title>
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<para>
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The Yocto Project team maintains complete source repositories for all Yocto Project files
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<ulink url='http://git.yoctoproject.org/cgit/cgit.cgi'>here</ulink>.
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This web-based source code browser is organized into categories by function such as
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IDE Plugins, Matchbox, Poky, Yocto Linux Kernel, and so forth.
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From the interface, you can click on any particular item in the "Name" column and
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see the URL at the bottom of the page that you need to set up a Git repository for
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that particular item.
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Having a local Git repository of the Yocto Project files allows you to
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make changes, contribute to the history, and ultimately enhance the Yocto Project's
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tools, Board Support Packages, and so forth.
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</para>
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<para>
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Conversely, if you are a developer that is not interested in contributing back to the
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Yocto Project, you have the ability to simply download and extract release tarballs
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and use them within the Yocto Project environment.
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All that is required is a particular release of Yocto Project, a kernel, and
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your application source code.
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</para>
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<para>
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For any supported release of Yocto Project, you can go to the Yocto Project website’s
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<ulink url='http://www.yoctoproject.org/download'>download page</ulink> and get a
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tarball of the release.
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You can also go to this site to download any supported BSP tarballs.
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Unpacking the tarball gives you a hierarchical directory structure of Yocto Project
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files that lets you develop using the Yocto Project.
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</para>
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<para>
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Once you are set up through either tarball extraction or creation of Git repositories,
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you are ready to develop.
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</para>
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<para>
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In summary, here is where you can get the Yocto Project files needed for development:
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<itemizedlist>
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<listitem><para><emphasis><ulink url='http://git.yoctoproject.org/cgit/cgit.cgi'>Source Repositories:</ulink></emphasis>
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This area contains IDE Plugins, Matchbox, Poky, Poky Support, Tools, Yocto Linux Kernel, and Yocto
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Metadata Layers.
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You can create Git repositories for each of these areas.</para>
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<para>
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<imagedata fileref="figures/source-repos.png" align="center" width="6in" depth="4in" />
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</para></listitem>
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<listitem><para><anchor id='index-downloads' /><emphasis><ulink url='http://autobuilder.yoctoproject.org/downloads/'>Index of /downloads:</ulink></emphasis>
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This area contains an index of downloads such as
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the <trademark class='trade'>Eclipse</trademark>
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Yocto Plug-in, miscellaneous support, Poky, pseudo, cross-development toolchains,
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and all released versions of Yocto Project in the form of images or tarballs.
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Downloading and extracting these files does not produce a Git repository but rather
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a snapshot of a particular release or image.
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[WRITER NOTE: link will be http://downloads.yoctoproject.org.]</para>
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<para>
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<imagedata fileref="figures/index-downloads.png" align="center" width="6in" depth="4in" />
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</para></listitem>
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<listitem><para><emphasis><ulink url='http://www.yoctoproject.org/download'>Yocto Project Download Page</ulink></emphasis>
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This page on the Yocto Project website allows you to download any Yocto Project
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release or Board Support Package (BSP) in tarball form.
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The tarballs are similar to those found in the
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<ulink url='http://autobuilder.yoctoproject.org/downloads/'>Index of /downloads:</ulink> area.</para>
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<para>
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<imagedata fileref="figures/yp-download.png" align="center" width="6in" depth="4in" />
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='yocto-project-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 Project development
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environment might find helpful.
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While some of these terms are universal, the list includes them just in case:
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<itemizedlist>
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<listitem><para><emphasis>Append Files:</emphasis> Files that append build information to
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a recipe file.
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Information in append files override the information in the similarly-named recipe file.
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Append files use the <filename>.bbappend</filename> filename suffix.</para></listitem>
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<listitem><para><emphasis>BitBake:</emphasis> The task executor and scheduler used by
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the Yocto Project to build images.
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For more information on BitBake, see the <ulink url='http://bitbake.berlios.de/manual/'>
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BitBake documentation</ulink>.</para></listitem>
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<listitem><para><emphasis>Classes:</emphasis> Files that provide for logic encapsulation
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and inheritance allowing commonly used patterns to be defined once and easily used
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in multiple recipes.
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Class files end with the <filename>.bbclass</filename> filename extension.</para></listitem>
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<listitem><para><emphasis>Configuration File:</emphasis> Configuration information in the
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<filename>.conf</filename> files provides global definitions of variables.
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The <filename>conf/local.conf</filename> configuration file in the Yocto Project
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build directory defines user-defined variables that affect each build.
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The <filename>distro/poky.conf</filename> configuration file also in the
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build directory 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 Yocto Project file structure, define
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variables for specific hardware and are only used when building for that target
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(e.g. the <filename>machine/beagleboard.conf</filename> configuration file defines
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variables for the Texas Instruments ARM Cortex-A8 development board).
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Configuration files end with a <filename>.conf</filename> filename extension.</para></listitem>
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<listitem><para><emphasis>Cross-Development Toolchain:</emphasis> A collection of software development
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tools and utilities that allow you to develop software for targeted architectures.
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This toolchain contains cross-compilers, linkers, and debuggers that are specific to
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an architecure.
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You can use the Yocto Project to build cross-development toolchains in tarball form that when
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unpacked contain the development tools you need to cross-compile and test your software.
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The Yocto Project ships with images that contain toolchains for supported architectures
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as well.
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Sometimes this toolchain is referred to as the meta-toolchain.</para></listitem>
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<listitem><para><emphasis>Image:</emphasis> An image is the result produced when
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BitBake processes a given collection of recipes and related metadata.
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Images are the binary output that runs on specific hardware and for specific
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use cases.
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For a list of the supported image types that the Yocto Project provides, see the
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"<ulink url='http://www.yoctoproject.org/docs/1.1/poky-ref-manual/poky-ref-manual.html#ref-images'>Reference: Images</ulink>"
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appendix in
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<ulink url='http://www.yoctoproject.org/docs/1.1/poky-ref-manual/poky-ref-manual.html'>
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The Yocto Project Reference Manual</ulink>.</para></listitem>
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<listitem><para><emphasis>Layer:</emphasis> A collection of recipes representing the core,
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a BSP, or an application stack.</para></listitem>
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<listitem><para><emphasis>Metadata:</emphasis> The files that BitBake parses when building an image.
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Metadata includes recipes, classes, and configuration files.</para></listitem>
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<listitem><para><emphasis>OE-Core:</emphasis> A core set of metadata originating
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with OpenEmbedded (OE) that is shared between OE and the Yocto Project.
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This metadata is found in the <filename>meta</filename> directory of the Yocto Project
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files.</para></listitem>
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<listitem><para><emphasis>Package:</emphasis> The packaged output from a baked recipe.
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A package is generally the compiled binaries produced from the recipe's sources.
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You ‘bake’ something by running it through BitBake.</para></listitem>
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<listitem><para><emphasis>Poky:</emphasis> The build tool that the Yocto Project
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uses to create images.</para></listitem>
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<listitem><para><emphasis>Recipe:</emphasis> A set of instructions for building packages.
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A recipe describes where you get source code and which patches to apply.
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Recipes describe dependencies for libraries or for other recipes, and they
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also contain configuration and compilation options.
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Recipes contain the logical unit of execution, the software/images to build, and
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use the <filename>.bb</filename> file extension.</para></listitem>
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<listitem><para><emphasis>Tasks:</emphasis> Arbitrary groups of software Recipes.
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You simply use Tasks to hold recipes that, when built, usually accomplish a single task.
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For example, a task could contain the recipes for a company’s proprietary or value-add software.
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Or, the task could contain the recipes that enable graphics.
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A task is really just another recipe.
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Because task files are recipes, they end with the <filename>.bb</filename> filename
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extension.</para></listitem>
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<listitem><para><emphasis>Upstream:</emphasis> A reference to source code or repositories
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that are not local to the development system but located in a master area that is controlled
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by the maintainer of the source code.
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For example, in order for a developer to work on a particular piece of code, they need to
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first get a copy of it from an "upstream" source.</para></listitem>
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<listitem><para><emphasis>Yocto Project Files:</emphasis>
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This term refers to the directory structure created as a result of downloading
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and unpacking a Yocto Project release tarball or setting up a Git repository
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by cloning <filename>git://git.yoctoproject.org/poky</filename>.
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Sometimes the term "the Yocto Project Files structure" is used as well.</para>
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<para>The Yocto Project files contain BitBake, Documentation, metadata and
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other files that all support the development environment.
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Consequently, you must have the Yocto Project files in place on your development
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system in order to do any development using the Yocto Project.</para>
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<para>The name of the top-level directory of the Yocto Project file structure
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is derived from the Yocto Project release tarball.
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For example, downloading and unpacking <filename>poky-edison-6.0.tar.bz2</filename>
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results in a Yocto Project file structure whose Yocto Project source directory is named
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<filename>poky-edison-6.0</filename>.
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If you create a Git repository, then you can name the repository anything you like.</para>
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<para>You can find instruction on how to set up the Yocto Project files on your
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host development system by reading
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the
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"<ulink url='http://www.yoctoproject.org/docs/1.1/dev-manual/dev-manual.html#getting-setup'>Getting
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Setup</ulink>" section.</para></listitem>
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<listitem><para><emphasis>Yocto Project Build Directory:</emphasis>
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This term refers to the area used by the Yocto Project for builds.
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The area is created when you <filename>source</filename> the Yocto Project setup
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environment script that is found in the Yocto Project files area.
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(e.g. <filename>oe-init-build-env</filename>).
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You can create the Yocto Project build directory anywhere you want on your
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development system.
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Here is an example that creates the directory in <filename>mybuilds</filename>
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and names the Yocto Project build directory <filename>YP-6.0</filename>:
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<literallayout class='monospaced'>
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$ source poky-edison-6.0/oe-init-build-env $HOME/mybuilds/YP-6.0
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</literallayout>
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If you don't specifically name the directory, BitBake creates it
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in the current directory and uses the name <filename>build</filename>.
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Also, if you supply an existing directory, then BitBake uses that
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directory as the Yocto Project build directory and populates the build hierarchy
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beneath it.</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='licensing'>
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<title>Licensing</title>
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<para>
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Because open source projects are open to the public, they have different licensing structures in place.
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License evolution for both Open Source and Free Software has an interesting history.
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If you are interested in this history, you can find basic information here:
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<itemizedlist>
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<listitem><para><ulink url='http://en.wikipedia.org/wiki/Open-source_license'>Open source license history</ulink>
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</para></listitem>
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<listitem><para><ulink url='http://en.wikipedia.org/wiki/Free_software_license'>Free software license
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history</ulink></para></listitem>
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</itemizedlist>
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</para>
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<para>
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In general, the Yocto Project is broadly licensed under the Massachusetts Institute of Technology
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(MIT) License.
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MIT licensing permits the reuse of software within proprietary software as long as the
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license is distributed with that software.
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MIT is also compatible with the GNU General Public License (GPL).
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Patches to the Yocto Project follow the upstream licensing scheme.
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You can find information on the MIT license at
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<ulink url='http://www.opensource.org/licenses/mit-license.php'>here</ulink>.
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You can find information on the GNU GPL <ulink url='http://www.opensource.org/licenses/LGPL-3.0'>
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here</ulink>.
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</para>
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<para>
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When you build an image using Yocto Project, the build process uses a known list of licenses to
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ensure compliance.
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Once the build completes, the list of all licenses found and used during the build are
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kept in the Yocto Project build directory at
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<filename>tmp/deploy/images/licenses</filename>.
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If a module requires a license that is not in the base list, the build process
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generates a warning during the build.
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These tools make it easier for a developer to be certain of the licenses with which
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their shipped products must comply.
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However, even with these tools it is still up to the developer to resolve potential licensing issues.
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</para>
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<para>
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The base list of licenses used by the build process is a combination of the Software Package
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Data Exchange (SPDX) list and the Open Source Initiative (OSI) projects.
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<ulink url='http://spdx.org'>SPDX Group</ulink> is a working group of the Linux Foundation
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that maintains a specification
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for a standard format for communicating the components, licenses, and copyrights
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associated with a software package.
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<ulink url='http://opensource.org'>OSI</ulink> is a corporation dedicated to the Open Source
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Definition and the effort for reviewing and approving licenses that are OSD-conformant.
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</para>
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<para>
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You can find a list of the combined SPDX and OSI licenses that the Yocto Project uses
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<ulink url='http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/files/common-licenses'>here</ulink>.
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This wiki page discusses the license infrastructure used by the Yocto Project.
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</para>
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</section>
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<section id='git'>
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<title>Git</title>
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<para>
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The Yocto Project uses Git, which is a free, open source distributed version control system.
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Git supports distributed development, non-linear development, and can handle large projects.
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It is best that you know how to work with Git if you are going to use Yocto Project for development.
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</para>
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<para>
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Git has an extensive set of commands that lets you manage changes and perform
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collaboration over the life of a project.
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Conveniently though, you can manage with a small set of basic operations and workflows
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once you understand the basic philosophy behind Git.
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You do not have to be an expert in Git to be functional.
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A good place to look for instruction on a minimal set of Git commands is
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<ulink url='http://git-scm.com/documentation'>here</ulink>.
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If you need to download Git, you can do so
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<ulink url='http://git-scm.com/download'>here</ulink>.
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</para>
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<para>
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Git works by using branching techniques that track content change (not files)
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within a project (e.g. a new feature or updated documentation).
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Creating a tree-like structure based on project divergence allows for excellent historical
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information over the life of a project.
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This methodology also allows for an environment in which you can do lots of
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experimentation on your project as you develop changes or new features.
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For example, you can create a “branch”, experiment with some feature, and then
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if you like the feature, you incorporate the branch into the tree.
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If you don’t, you cut the branch off by deleting it.
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</para>
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<para>
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If you don’t know much about Git, we suggest you educate
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yourself by visiting the links previously mentioned.
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</para>
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<para>
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The following list briefly describes some basic Git operations as a way to get started.
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As with any set of commands, this list (in most cases) simply shows the base command and
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omits the many arguments they support.
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See the Git documentation for complete descriptions and strategies on how to use these commands:
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<itemizedlist>
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<listitem><para><emphasis><filename>git init</filename>:</emphasis> Initializes an empty Git repository.
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You cannot use Git commands unless you have a <filename>.git</filename> repository.</para></listitem>
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<listitem><para><emphasis><filename>git clone</filename>:</emphasis> Creates a clone of a repository.
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During collaboration, this command allows you to create a local repository that is on
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equal footing with a fellow developer’s repository.</para></listitem>
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<listitem><para><emphasis><filename>git add</filename>:</emphasis> Adds updated file contents
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to the index that
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Git uses to track changes.
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You must add all files that have changed before you can commit them.</para></listitem>
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<listitem><para><emphasis><filename>git commit</filename>:</emphasis> Creates a “commit” that documents
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the changes you made.
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Commits are used for historical purposes, for determining if a maintainer of a project
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will allow the change, and for ultimately pushing the change from your local Git repository
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into the project’s upstream (or master) repository.</para></listitem>
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<listitem><para><emphasis><filename>git status</filename>:</emphasis> Reports any modified files that
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possibly need added and committed.</para></listitem>
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<listitem><para><emphasis><filename>git checkout <branch-name></filename>:</emphasis> Changes
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your working branch.
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This command is analogous to “cd”.</para></listitem>
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<listitem><para><emphasis><filename>git checkout –b <working-branch></filename>:</emphasis> Creates
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a working branch on your local machine where you can isolate work.
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It is a good idea to use local branches when adding specific features or changes.
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This way if you don’t like what you have done you can easily get rid of the work.</para></listitem>
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<listitem><para><emphasis><filename>git branch</filename>:</emphasis> Reports existing branches and
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tells you which branch in which you are currently working.</para></listitem>
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<listitem><para><emphasis><filename>git branch -D <branch-name></filename>:</emphasis>
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Deletes an existing branch.
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You need to be in a branch other than the one you are deleting
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in order to delete <branch-name>.</para></listitem>
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<listitem><para><emphasis><filename>git pull</filename>:</emphasis> Retrieves information
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from an upstream Git
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repository and places it in your local Git repository.
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You use this command to make sure you are synchronized with the repository
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from which you are basing changes (.e.g. the master repository).</para></listitem>
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<listitem><para><emphasis><filename>git push</filename>:</emphasis> Sends all your local changes you
|
||
have committed to an upstream Git repository (e.g. a contribution repository).
|
||
The maintainer of the project draws from these repositories when adding your changes to the
|
||
project’s master repository.</para></listitem>
|
||
<listitem><para><emphasis><filename>git merge</filename>:</emphasis> Combines or adds changes from one
|
||
local branch of your repository with another branch.
|
||
When you create a local Git repository, the default branch is named “master”.
|
||
A typical workflow is to create a temporary branch for isolated work, make and commit your
|
||
changes, switch to your local master branch, merge the changes from the temporary branch into the
|
||
local master branch, and then delete the temporary branch.</para></listitem>
|
||
<listitem><para><emphasis><filename>git cherry-pick</filename>:</emphasis> Choose and apply specific
|
||
commits from one branch into another branch.
|
||
There are times when you might not be able to merge all the changes in one branch with
|
||
another but need to pick out certain ones.</para></listitem>
|
||
<listitem><para><emphasis><filename>gitk</filename>:</emphasis> Provides a GUI view of the branches
|
||
and changes in your local Git repository.
|
||
This command is a good way to graphically see where things have diverged in your
|
||
local repository.</para></listitem>
|
||
<listitem><para><emphasis><filename>git log</filename>:</emphasis> Reports a history of your changes to the
|
||
repository.</para></listitem>
|
||
<listitem><para><emphasis><filename>git diff</filename>:</emphasis> Displays line-by-line differences
|
||
between your local working files and the same files in the upstream Git repository that your
|
||
branch currently tracks.</para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
</section>
|
||
|
||
<section id='workflows'>
|
||
<title>Workflows</title>
|
||
|
||
<para>
|
||
This section provides some overview on workflows using Git.
|
||
In particular, the information covers basic practices that describe roles and actions in a
|
||
collaborative development environment.
|
||
Again, if you are familiar with this type of development environment, you might want to just
|
||
skip the section.
|
||
</para>
|
||
|
||
<para>
|
||
The Yocto Project files are maintained using Git in a "master" branch whose Git history
|
||
tracks every change and whose structure provides branches for all diverging functionality.
|
||
Although there is no need to use Git, many open source projects do so.
|
||
For the Yocto Project, a key individual called the "maintainer" is responsible for the "master"
|
||
branch of the Git repository.
|
||
The "master" branch is the “upstream” repository where the final builds of the project occur.
|
||
The maintainer is responsible for allowing changes in from other developers and for
|
||
organizing the underlying branch structure to reflect release strategies and so forth.
|
||
<note>You can see who is the maintainer for Yocto Project files by examining the
|
||
<filename>distro_tracking_fields</filename> file in the Yocto Project
|
||
<filename>meta/conf/distro/include</filename> directory.</note>
|
||
</para>
|
||
|
||
<para>
|
||
The project also has contribution repositories known as “contrib” areas.
|
||
These areas temporarily hold changes to the project that have been submitted or committed
|
||
by the Yocto Project development team and by community members that contribute to the project.
|
||
The maintainer determines if the changes are qualified to be moved from the "contrib" areas
|
||
into the "master" branch of the Git repository.
|
||
</para>
|
||
|
||
<para>
|
||
Developers (including contributing community members) create and maintain cloned repositories
|
||
of the upstream "master" branch.
|
||
These repositories are local to their development platforms and are used to develop changes.
|
||
When a developer is satisfied with a particular feature or change, they “push” the changes
|
||
to the appropriate "contrib" repository.
|
||
</para>
|
||
|
||
<para>
|
||
Developers are responsible for keeping their local repository up-to-date with "master".
|
||
They are also responsible for straightening out any conflicts that might arise within files
|
||
that are being worked on simultaneously by more than one person.
|
||
All this work is done locally on the developer’s machine before anything is pushed to a
|
||
"contrib" area and examined at the maintainer’s level.
|
||
</para>
|
||
|
||
<para>
|
||
A somewhat formal method exists by which developers commit changes and push them into the
|
||
"contrib" area and subsequently request that the maintainer include them into "master"
|
||
This process is called “submitting a patch” or “submitting a change.”
|
||
</para>
|
||
|
||
<para>
|
||
To summarize the environment: we have a single point of entry for changes into the project’s
|
||
"master" branch of the Git repository, which is controlled by the project’s maintainer.
|
||
And, we have a set of developers who independently develop, test, and submit changes
|
||
to "contrib" areas for the maintainer to examine.
|
||
The maintainer then chooses which changes are going to become permanently a part of the project.
|
||
</para>
|
||
|
||
<para>
|
||
<imagedata fileref="figures/git-workflow.png" width="6in" depth="3in" align="left" scalefit="1" />
|
||
</para>
|
||
|
||
<para>
|
||
While each development environment is unique, there are some best practices or methods
|
||
that help development run smoothly.
|
||
The following list describes some of these practices.
|
||
For more detailed information about these strategies see
|
||
<ulink url='http://www.kernel.org/pub/software/scm/git/docs/gitworkflows.html'>Git Workflows</ulink>.
|
||
<itemizedlist>
|
||
<listitem><para><emphasis>Make Small Changes:</emphasis> It is best to keep your changes you commit
|
||
small as compared to bundling many disparate changes into a single commit.
|
||
This practice not only keeps things manageable but also allows the maintainer
|
||
to more easily include or refuse changes.</para>
|
||
<para>It is also good practice to leave the repository in a state that allows you to
|
||
still successfully build your project.</para></listitem>
|
||
<listitem><para><emphasis>Use Branches Liberally:</emphasis> It is very easy to create, use, and
|
||
delete local branches in your working Git repository.
|
||
You can name these branches anything you like.
|
||
It is helpful to give them names associated with the particular feature or change
|
||
on which you are working.
|
||
Once you are done with a feature or change, simply discard the branch.</para></listitem>
|
||
<listitem><para><emphasis>Merge Changes:</emphasis> The <filename>git merge</filename>
|
||
command allows you to take the
|
||
changes from one branch and fold them into another branch.
|
||
This process is especially helpful when more than a single developer might be working
|
||
on different parts of the same feature.
|
||
Merging changes also automatically identifies any collisions or “conflicts”
|
||
that might happen as a result of the same lines of code being altered by two different
|
||
developers.</para></listitem>
|
||
<listitem><para><emphasis>Manage Branches:</emphasis> Because branches are easy to use, you should
|
||
use a system where branches indicate varying levels of code readiness.
|
||
For example, you can have a “work” branch to develop in, a “test” branch where the code or
|
||
change is tested, a “stage” branch where changes are ready to be committed, and so forth.
|
||
As your project develops, you can merge code across the branches to reflect ever-increasing
|
||
stable states of the development.</para></listitem>
|
||
<listitem><para><emphasis>Use Push and Pull:</emphasis> The push-pull workflow is based on the
|
||
concept of developers “pushing” local commits to a remote repository, which is
|
||
usually a contribution repository.
|
||
This workflow is also based on developers “pulling” known states of the project down into their
|
||
local development repositories.
|
||
The workflow easily allows you to pull changes submitted by other developers from the
|
||
upstream repository into your work area ensuring that you have the most recent software
|
||
on which to develop.
|
||
The Yocto Project has two scripts named <filename>create-pull-request</filename> and
|
||
<filename>send-pull-request</filename> that ship with the release to facilitate this
|
||
workflow.
|
||
You can find these scripts in the local Yocto Project files Git repository in
|
||
<filename>scripts</filename>.</para></listitem>
|
||
<listitem><para><emphasis>Patch Workflow:</emphasis> This workflow allows you to notify the
|
||
maintainer through an email that you have a change (or patch) you would like considered
|
||
for the "master" branch of the Git repository.
|
||
To send this type of change you format the patch and then send the email using the Git commands
|
||
<filename>git format-patch</filename> and <filename>git send-email</filename>.
|
||
You can find information on how to submit later in this chapter.</para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
</section>
|
||
|
||
<section id='tracking-bugs'>
|
||
<title>Tracking Bugs</title>
|
||
|
||
<para>
|
||
The Yocto Project uses <ulink url='http://www.bugzilla.org/about/'>Bugzilla</ulink> to track bugs.
|
||
This bug-tracking application works well for group development because it tracks bugs and code
|
||
changes, can be used to communicate changes and problems with developers, can be used to
|
||
submit and review patches, and can be used to manage quality assurance.
|
||
You can find a good overview of Bugzilla <ulink url='http://www.bugzilla.org/about/'>here</ulink>.
|
||
</para>
|
||
|
||
<para>
|
||
Sometimes it is helpful to submit, investigate, or track a bug against the Yocto Project itself
|
||
such as when discovering an issue with some component of the build system that acts contrary
|
||
to the documentation or your expectations.
|
||
You can find information
|
||
for Bugzilla configuration and bug tracking procedures specific to the Yocto Project
|
||
<ulink url='https://wiki.yoctoproject.org/wiki/Bugzilla_Configuration_and_Bug_Tracking'>here</ulink>.
|
||
</para>
|
||
|
||
<para>
|
||
The Yocto Project uses its own version of the Bugzilla application.
|
||
You can find the home page <ulink url='http://bugzilla.yoctoproject.org'>here</ulink>.
|
||
You need to use this implementation of Bugzilla when logging a defect against anything released
|
||
by the Yocto Project team.
|
||
</para>
|
||
|
||
<para>
|
||
Here are some things to remember when dealing with bugs against the Yocto Project:
|
||
<itemizedlist>
|
||
<listitem><para>The Yocto Project follows a bug-naming convention:
|
||
<filename>[YOCTO #<number>]</filename>, where <filename><number></filename> is the
|
||
assigned defect ID used in Bugzilla.
|
||
So, for example, a valid way to refer to a defect when creating a commit comment
|
||
would be <filename>[YOCTO #1011]</filename>.
|
||
This convention becomes important if you are submitting patches against the Yocto Project
|
||
code itself.
|
||
See the following section for more information.</para></listitem>
|
||
<listitem><para>Defects for Yocto Project fall into one of four classifications: Yocto Projects,
|
||
Infrastructure, Poky, and Yocto Metadata Layers.</para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
</section>
|
||
|
||
<section id='how-to-submit-a-change'>
|
||
<title>How to Submit a Change</title>
|
||
|
||
<para>
|
||
Contributions to the Yocto Project are very welcome.
|
||
You should send patches to the appropriate Yocto Project mailing list to get them
|
||
in front of the Yocto Project Maintainer.
|
||
For a list of the Yocto Project mailing lists, see the
|
||
"<ulink url='http://www.yoctoproject.org/docs/1.1/poky-ref-manual/poky-ref-manual.html#resources-mailinglist'>Mailing lists</ulink>" section in
|
||
<ulink url='http://www.yoctoproject.org/docs/1.1/poky-ref-manual/poky-ref-manual.html'> The
|
||
Yocto Project Reference Manual</ulink>.
|
||
</para>
|
||
|
||
<para>
|
||
Following is some guidance on which mailing list to use for what type of defect:
|
||
<itemizedlist>
|
||
<listitem><para>For defects against the Yocto Project build system Poky, send
|
||
your patch to the
|
||
<ulink url='http://lists.yoctoproject.org/listinfo/poky'></ulink> mailing list.
|
||
This mailing list corresponds to issues that are not specific to the Yocto Project but
|
||
are part of the OE-core.
|
||
For example, a defect against anything in the <filename>meta</filename> layer
|
||
or the BitBake Manual could be sent to this mailing list.</para></listitem>
|
||
<listitem><para>For defects against Yocto-specific layers, tools, and Yocto Project
|
||
documentation use the
|
||
<ulink url='http://lists.yoctoproject.org/listinfo/yocto'></ulink> mailing list.
|
||
This mailing list corresponds to Yocto-specific areas such as
|
||
<filename>meta-yocto</filename>, <filename>meta-intel</filename>,
|
||
<filename>linux-yocto</filename>, and <filename>documentation</filename>.</para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
|
||
<para>
|
||
When you send a patch, be sure to include a "signed-off-by:"
|
||
line in the same style as required by the Linux kernel.
|
||
Adding this line signifies the developer has agreed to the Developer's Certificate of Origin 1.1
|
||
as follows:
|
||
<literallayout class='monospaced'>
|
||
Developer's Certificate of Origin 1.1
|
||
|
||
By making a contribution to this project, I certify that:
|
||
|
||
(a) The contribution was created in whole or in part by me and I
|
||
have the right to submit it under the open source license
|
||
indicated in the file; or
|
||
|
||
(b) The contribution is based upon previous work that, to the best
|
||
of my knowledge, is covered under an appropriate open source
|
||
license and I have the right under that license to submit that
|
||
work with modifications, whether created in whole or in part
|
||
by me, under the same open source license (unless I am
|
||
permitted to submit under a different license), as indicated
|
||
in the file; or
|
||
|
||
(c) The contribution was provided directly to me by some other
|
||
person who certified (a), (b) or (c) and I have not modified
|
||
it.
|
||
|
||
(d) I understand and agree that this project and the contribution
|
||
are public and that a record of the contribution (including all
|
||
personal information I submit with it, including my sign-off) is
|
||
maintained indefinitely and may be redistributed consistent with
|
||
this project or the open source license(s) involved.
|
||
</literallayout>
|
||
A Poky contributions tree (<filename>poky-contrib</filename>,
|
||
<filename>git://git.yoctoproject.org/poky-contrib.git</filename>)
|
||
exists for contributors to stage contributions.
|
||
If people desire such access, please ask on the mailing list.
|
||
Usually, the Yocto Project team will grant access to anyone with a proven track
|
||
record of good patches.
|
||
</para>
|
||
|
||
<para>
|
||
In a collaborative environment, it is necessary to have some sort of standard
|
||
or method through which you submit changes.
|
||
Otherwise, things could get quite chaotic.
|
||
</para>
|
||
|
||
<para>
|
||
When you form a commit, you must follow certain standards established by the
|
||
Yocto Project development team.
|
||
For each commit, you must provide a single-line summary of the change and you
|
||
almost always provide a more detailed description of what you did (i.e. the body
|
||
of the commit).
|
||
The only exceptions for not providing a detailed description would be if your
|
||
change is a simple, self-explanatory change that needs no description.
|
||
Here are the Yocto Project commit message guidelines:
|
||
<itemizedlist>
|
||
<listitem><para>Provide a single-line, short summary of the change.
|
||
This summary is typically viewable by source control systems.
|
||
Thus, providing something short and descriptive that gives the reader
|
||
a summary of the change is useful when viewing a list of many commits.
|
||
</para></listitem>
|
||
<listitem><para>For the body of the commit message, provide detailed information
|
||
that describes what you changed, why you made the change, and the approach
|
||
you used.
|
||
Provide as much detail as you can in the body of the commit message.
|
||
</para></listitem>
|
||
<listitem><para>If the change addresses a specific bug or issue that is
|
||
associated with a bug-tracking ID, prefix your detailed description
|
||
with the bug or issue ID.
|
||
For example, the Yocto Project tracks bugs using a bug-naming convention.
|
||
Any commits that address a bug must start with the bug ID in the description
|
||
as follows:
|
||
<literallayout class='monospaced'>
|
||
YOCTO #<bug-id>: <Detailed description of commit>
|
||
</literallayout></para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
|
||
<para>
|
||
You can find more guidance on creating well-formed commit messages at this OpenEmbedded
|
||
wiki page:
|
||
<ulink url='http://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines'></ulink>.
|
||
</para>
|
||
|
||
<para>
|
||
Following are general instructions for both pushing changes upstream and for submitting changes as patches.
|
||
</para>
|
||
|
||
<section id='pushing-a-change-upstream'>
|
||
<title>Pushing a Change Upstream and Requesting a Pull</title>
|
||
|
||
<para>
|
||
The basic flow for pushing a change to an upstream "contrib" Git repository is as follows:
|
||
<itemizedlist>
|
||
<listitem><para>Make your changes in your local Git repository.</para></listitem>
|
||
<listitem><para>Stage your commit (or change) by using the <filename>git add</filename>
|
||
command.</para></listitem>
|
||
<listitem><para>Commit the change by using the <filename>git commit</filename>
|
||
command and push it to the "contrib" repository.
|
||
Be sure to provide a commit message that follows the project’s commit standards
|
||
as described earlier.</para></listitem>
|
||
<listitem><para>Notify the maintainer that you have pushed a change by making a pull
|
||
request.
|
||
The Yocto Project provides two scripts that conveniently let you generate and send
|
||
pull requests to the Yocto Project.
|
||
These scripts are <filename>create-pull-request</filename> and
|
||
<filename>send-pull-request</filename>.
|
||
You can find these scripts in the <filename>scripts</filename> directory of the
|
||
Yocto Project file structure.</para>
|
||
<para>For help on using these scripts, simply provide the
|
||
<filename>--help</filename> argument as follows:
|
||
<literallayout class='monospaced'>
|
||
$ ~/poky/scripts/create-pull-request --help
|
||
$ ~/poky/scripts/send-pull-request --help
|
||
</literallayout></para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
|
||
<para>
|
||
You can find general Git information on how to push a change upstream
|
||
<ulink url='http://www.kernel.org/pub/software/scm/git/docs/user-manual.html#Developing-With-git'>
|
||
here</ulink>.
|
||
</para>
|
||
</section>
|
||
|
||
<section id='submitting-a-patch'>
|
||
<title>Submitting a Patch Through Email</title>
|
||
|
||
<para>
|
||
If you have a just a few changes, you can commit them and then submit them as an
|
||
email to the maintainer.
|
||
Here is a general procedure:
|
||
<itemizedlist>
|
||
<listitem><para>Make your changes in your local Git repository.</para></listitem>
|
||
<listitem><para>Stage your commit (or change) by using the <filename>git add</filename>
|
||
command.</para></listitem>
|
||
<listitem><para>Commit the change by using the
|
||
<filename>git commit --signoff</filename> command.
|
||
Using the <filename>--signoff</filename> option identifies you as the person
|
||
making the change and also satisfies the Developer's Certificate of
|
||
Origin (DCO) shown earlier.</para>
|
||
<para>When you form a commit you must follow certain standards established by the
|
||
Yocto Project development team.
|
||
See the earlier section
|
||
"<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
|
||
for Yocto Project commit message standards.</para></listitem>
|
||
<listitem><para>Format the commit into an email messsage.
|
||
To format commits, use the <filename>git format-patch</filename> command.
|
||
When you provide the command, you must include a revision list or a number of patches
|
||
as part of the command.
|
||
For example, these two commands each take the most recent single commit and
|
||
format it as an email message in the current directory:
|
||
<literallayout class='monospaced'>
|
||
$ git format-patch -1
|
||
$ git format-patch HEAD~
|
||
</literallayout></para>
|
||
<para>After the command is run, the current directory contains a
|
||
numbered <filename>.patch</filename> file for the commit.</para>
|
||
<para>If you provide several commits as part of the command,
|
||
the <filename>git format-patch</filename> command produces a numbered
|
||
series of files in the current directory – one for each commit.
|
||
For information on the <filename>git format-patch</filename> command,
|
||
see <filename>GIT_FORMAT_PATCH(1)</filename> displayed using the
|
||
<filename>man git-format-patch</filename> command.</para></listitem>
|
||
<listitem><para>Import the files into your mail client by using the
|
||
<filename>git send-email</filename> command.
|
||
<note>In order to use <filename>git send-email</filename>, you must have the
|
||
the proper Git packages installed.
|
||
For Ubuntu and Fedora the package is <filename>git-email</filename>.</note></para>
|
||
<para>The <filename>git send-email</filename> command sends email by using a local
|
||
or remote Mail Transport Agent (MTA) such as
|
||
<filename>msmtp</filename>, <filename>sendmail</filename>, or through a direct
|
||
<filename>smtp</filename> configuration in your Git <filename>config</filename>
|
||
file.</para>
|
||
<para>The <filename>git send-email</filename> command is the preferred method
|
||
for sending your patches since there is no risk of compromising whitespace
|
||
in the body of the message, which can occur when you use your own mail client.
|
||
The command also has several options that let you
|
||
specify recipients and perform further editing of the email message.
|
||
For information on how to use the <filename>git send-email</filename> command,
|
||
use the <filename>man git-send-email</filename> command.</para></listitem>
|
||
</itemizedlist>
|
||
</para>
|
||
</section>
|
||
</section>
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
</chapter>
|
||
<!--
|
||
vim: expandtab tw=80 ts=4
|
||
-->
|