path: root/documentation/dev-manual/dev-manual-start.xml

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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

<chapter id='dev-manual-start'>

<title>Getting Started with the Yocto Project</title>

<para>
    This chapter provides procedures related to getting set up to use the
    Yocto Project.
    For a more front-to-end process that takes you from minimally preparing
    a build host through building an image, see the
    <ulink url='&YOCTO_DOCS_QS_URL;'>Yocto Project Quick Start</ulink>.
</para>

<section id='setting-up-the-development-host-to-use-the-yocto-project'>
    <title>Setting Up the Development Host to Use the Yocto Project</title>

    <para>
        This section provides procedures to set up your development host to
        use the Yocto Project.
        For a Linux system to use the Yocto Project, you need to be sure
        you are running a supported Linux distribution and have the proper
        host packages installed.
        If you are using
        <ulink url='https://git.yoctoproject.org/cgit/cgit.cgi/crops/about/'>CROPS</ulink>
        that leverages
        <ulink url='https://www.docker.com/'>Docker Containers</ulink>,
        host setup differs from that of a native Linux machine.
    </para>

    <section id='setting-up-a-native-linux-host'>
        <title>Setting Up a Native Linux Host</title>

        <para role='writernotes'>
            Need text - Following is some basics for a Linux host system.
            This information needs to be worked in.
        </para>

        <para>
            Setup consists of making sure you have a supported operating system,
            installing host packages, and Here is what you need to use the Yocto Project:
            <itemizedlist>
                <listitem><para>
                    <emphasis>Host System:</emphasis>
                    You should have a reasonably current Linux-based host
                    system.
                    You will have the best results with a recent release of
                    Fedora, openSUSE, Debian, Ubuntu, or CentOS as these
                    releases are frequently tested against the Yocto Project
                    and officially supported.
                    For a list of the distributions under validation and their
                    status, see the
                    "<ulink url='&YOCTO_DOCS_REF_URL;#detailed-supported-distros'>Supported Linux Distributions</ulink>" section
                    in the Yocto Project Reference Manual and the wiki page at
                    <ulink url='&YOCTO_WIKI_URL;/wiki/Distribution_Support'>Distribution Support</ulink>.</para>
                    <para>
                    You should also have about 50 Gbytes of free disk space
                    for building images.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Packages:</emphasis>
                    The OpenEmbedded build system requires that certain
                    packages exist on your development system
                    (e.g. Python 2.7).
                    See the
                    "<ulink url='&YOCTO_DOCS_QS_URL;#packages'>Build Host Packages</ulink>"
                    section in the Yocto Project Quick Start and the
                    "<ulink url='&YOCTO_DOCS_REF_URL;#required-packages-for-the-host-development-system'>Required Packages for the Host Development System</ulink>"
                    section in the Yocto Project Reference Manual for the
                    exact package requirements and the installation commands
                    to install them for the supported distributions.
                    </para></listitem>
            </itemizedlist>
        </para>
    </section>

    <section id='setting-up-to-use-crops'>
        <title>Setting Up to Use CROPS</title>

        <para role='writernotes'>
            Need text.
            With CROPS, not sure what the basic package requirements are.
            Need to find this out.
        </para>
    </section>

    <section id='setting-up-bsp-layers'>
        <title>Setting Up BSP Layers</title>

        <para>
            This section describes how to set up a layer for a Board Support
            Package (BSP).
            For structural information on BSPs, see the
            <ulink url='&YOCTO_DOCS_BSP_URL;#bsp-guide'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
            <orderedlist>
                <listitem><para>
                    <emphasis>Determine the BSP Layer You Want:</emphasis>
                    The Yocto Project supports many BSPs, which are maintained in
                    their own layers or in layers designed to contain several
                    BSPs.
                    To get an idea of machine support through BSP layers, you can
                    look at the
                    <ulink url='&YOCTO_RELEASE_DL_URL;/machines'>index of machines</ulink>
                    for the release.
                    <note>
                        The Yocto Project uses the following BSP layer naming
                        scheme:
                        <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>
                        </literallayout>
                        where <replaceable>bsp_name</replaceable> is the recognized
                        BSP name.
                        Here is an example:
                        <literallayout class='monospaced'>
     meta-raspberrypi
                        </literallayout>
                        See the
                        "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
                        section in the Yocto Project Board Support Package (BSP)
                        Developer's Guide for more information on BSP Layers.
                    </note>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Optionally Set Up the <filename>meta-intel</filename> BSP Layer:</emphasis>
                    If your hardware is based on current Intel CPUs and devices,
                    you can leverage this BSP layer.
                    For details on the <filename>meta-intel</filename> BSP layer,
                    see the layer's
                    <ulink url='http://git.yoctoproject.org/cgit/cgit.cgi/meta-intel/tree/README'><filename>README</filename></ulink>
                    file.
                    <orderedlist>
                        <listitem><para>
                            <emphasis>Navigate to Your Source Directory:</emphasis>
                            Typically, you set up the
                            <filename>meta-intel</filename> Git repository
                            inside the
                            <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
                            (e.g. <filename>poky</filename>).
                            </para></listitem>
                        <listitem><para>
                            <emphasis>Clone the Layer:</emphasis>
                            <literallayout class='monospaced'>
     $ git clone git://git.yoctoproject.org/meta-intel.git
     Cloning into 'meta-intel'...
     remote: Counting objects: 14224, done.
     remote: Compressing objects: 100% (4591/4591), done.
     remote: Total 14224 (delta 8245), reused 13985 (delta 8006)
     Receiving objects: 100% (14224/14224), 4.29 MiB | 2.90 MiB/s, done.
     Resolving deltas: 100% (8245/8245), done.
     Checking connectivity... done.
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            <emphasis>Check Out the Proper Branch:</emphasis>
                            The branch you check out for
                            <filename>meta-intel</filename> must match the same
                            branch you are using for the Yocto Project release
                            (e.g. &DISTRO_NAME_NO_CAP;):
                            <literallayout class='monospaced'>
     $ git checkout <replaceable>branch_name</replaceable>
                            </literallayout>
                            For an example on how to discover branch names and
                            checkout on a branch, see the
                            "<link linkend='checking-out-by-branch-in-poky'>Checking Out By Branch in Poky</link>"
                            section.
                            </para></listitem>
                    </orderedlist>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Optionally Set Up an Alternative BSP Layer:</emphasis>
                    If your hardware can be more closely leveraged to an
                    existing BSP not within the <filename>meta-intel</filename>
                    BSP layer, you can clone that BSP layer.</para>

                    <para>The process is identical to the process used for the
                    <filename>meta-intel</filename> layer except for the layer's
                    name.
                    For example, if you determine that your hardware most
                    closely matches the <filename>meta-minnow</filename>,
                    clone that layer:
                    <literallayout class='monospaced'>
     $ git clone git://git.yoctoproject.org/meta-minnow
     Cloning into 'meta-minnow'...
     remote: Counting objects: 456, done.
     remote: Compressing objects: 100% (283/283), done.
     remote: Total 456 (delta 163), reused 384 (delta 91)
     Receiving objects: 100% (456/456), 96.74 KiB | 0 bytes/s, done.
     Resolving deltas: 100% (163/163), done.
     Checking connectivity... done.
                    </literallayout>
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='local-kernel-files'>
        <title>Setting Up to Work on a Kernel</title>

        <para>
            Kernel development is best accomplished using
            <ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename></ulink>
            and not through traditional kernel workflow methods.
            This section provides procedures to set up for both.
        </para>

        <section id='getting-ready-to-develop-using-devtool'>
            <title>Getting Ready to Develop using <filename>devtool</filename></title>

            <para role='writernotes'>
                Need the updated wiki stuff here
            </para>
        </section>

        <section id='getting-ready-for-traditional-kernel-development'>
            <title>Getting Ready for Traditional Kernel Development</title>

            <para>
                For traditional kernel development using the Yocto
                Project, you need to establish local copies of the
                kernel source.
                You can find Git repositories of supported Yocto Project
                kernels organized under "Yocto Linux Kernel" in the Yocto
                Project Source Repositories at
                <ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink>.
            </para>

            <para>
                This setup can involve creating a bare clone of the
                Yocto Project kernel and then copying that cloned
                repository.
                You can create the bare clone and the copy of the bare
                clone anywhere you like.
                For simplicity, it is recommended that you create these
                structures outside of the
                <ulink url='&YOCTO_DOCS_REF_URL;source-directory'>Source Directory</ulink>,
                which is usually named <filename>poky</filename>.
            </para>

            <para>
                The following steps show how to create a bare clone of the
                <filename>linux-yocto-4.4</filename> kernel and then
                create a copy of that clone:
                <note>
                    When you have a local Yocto Project kernel Git
                    repository, you can reference that repository rather than
                    the upstream Git repository as part of the
                    <filename>clone</filename> command.
                    Doing so can speed up the process.
                </note>
                <orderedlist>
                    <listitem><para>
                        <emphasis>Create the Bare Clone:</emphasis>
                        In the following example, the bare clone is named
                        <filename>linux-yocto-4.4.git</filename>:
                        <literallayout class='monospaced'>
     $ git clone &dash;&dash;bare git://git.yoctoproject.org/linux-yocto-4.4 linux-yocto-4.4.git
     Cloning into bare repository 'linux-yocto-4.4.git'...
     remote: Counting objects: 4543903, done.
     remote: Compressing objects: 100% (695618/695618), done.
     remote: Total 4543903 (delta 3818435), reused 4541724 (delta 3816256)
     Receiving objects: 100% (4543903/4543903), 801.08 MiB | 6.55 MiB/s, done.
     Resolving deltas: 100% (3818435/3818435), done.
     Checking connectivity... done.
                         </literallayout>
                         </para></listitem>
                    <listitem><para>
                        <emphasis>Create the Copy of the Bare Clone:</emphasis>
                        In the following command, the copy of the bare clone
                        is named <filename>my-linux-yocto-4.4-work</filename>:
                        <literallayout class='monospaced'>
     $ git clone linux-yocto-4.4.git my-linux-yocto-4.4-work
     Cloning into 'my-linux-yocto-4.4-work'...
     done.
     Checking out files: 100% (52221/52221), done.
                        </literallayout>
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Cloning the <filename>meta-yocto-kernel-extras</filename> Repository:</emphasis>
                        The <filename>meta-yocto-kernel-extras</filename> Git
                        repository contains Metadata needed only if you are
                        modifying and building the kernel image.
                        In particular, it contains the kernel BitBake append
                        (<filename>.bbappend</filename>) files that you edit to
                        point to your locally modified kernel source files and to
                        build the kernel image.
                        Pointing to these local files is much more efficient than
                        requiring a download of the kernel's source files from
                        upstream each time you make changes to the kernel.</para>

                        <para>You can find the
                        <filename>meta-yocto-kernel-extras</filename> Git
                        Repository in the "Yocto Metadata Layers" area of the
                        Yocto Project Source Repositories at
                        <ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink>.
                        It is good practice to create this Git repository
                        inside the Source Directory.</para>

                        <para>Following is an example that creates the
                        <filename>meta-yocto-kernel-extras</filename> Git
                        repository inside the Source Directory, which is named
                        <filename>poky</filename>, in this case:
                        <literallayout class='monospaced'>
     $ cd ~/poky
     $ git clone git://git.yoctoproject.org/meta-yocto-kernel-extras meta-yocto-kernel-extras
     Cloning into 'meta-yocto-kernel-extras'...
     remote: Counting objects: 727, done.
     remote: Compressing objects: 100% (452/452), done.
     remote: Total 727 (delta 260), reused 719 (delta 252)
     Receiving objects: 100% (727/727), 536.36 KiB | 0 bytes/s, done.
     Resolving deltas: 100% (260/260), done.
     Checking connectivity... done.
                        </literallayout>
                        </para></listitem>
                </orderedlist>
            </para>
        </section>
    </section>

    <section id='setting-up-to-use-eclipse'>
        <title>Setting Up to Use Eclipse</title>

        <para>
            This section presents the steps needed to set up your host if you
            are going to be using the popular
            <trademark class='trade'>Eclipse</trademark> IDE.
            The steps in this procedure are links to sections in the
            Yocto Project Software Development Kit (SDK) Developer's Guide
            that provide detailed procedures given the Neon version of
            Eclipse.
            For procedures on the entire development process using
            Eclipse, see the
            "<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-developing-applications-using-eclipse'>Developing Applications Using Eclipse</ulink>"
            section in the Yocto Project Software Development Kit (SDK)
            Developer's Guide.
            <orderedlist>
                <listitem><para>
                    <emphasis>Install Eclipse:</emphasis>
                    See the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#neon-installing-eclipse-ide'>Installing the Neon Eclipse IDE</ulink>"
                    section.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Configure Eclipse:</emphasis>
                    See the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#neon-configuring-the-mars-eclipse-ide'>Configuring the Neon Eclipse IDE</ulink>"
                    section.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Configure Eclipse:</emphasis>
                    See the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#neon-installing-the-eclipse-yocto-plug-in'>Installing or Accessing the Neon Eclipse Yocto Plug-in</ulink>"
                    section.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Configure Eclipse:</emphasis>
                    See the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#neon-configuring-the-eclipse-yocto-plug-in'>Configuring the Neon Eclipse Yocto Plug-in</ulink>"
                    section.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>
</section>

<section id='working-with-yocto-project-source-files'>
    <title>Working With Yocto Project Source Files</title>

    <para>
        This section contains procedures related to locating and securing
        Yocto Project files.
        You establish and use these local files to work on projects.
        <note><title>Notes</title>
            <itemizedlist>
                <listitem><para>
                    For concepts and introductory information about Git as it
                    is used in the Yocto Project, see the
                    "<ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink>"
                    section in the Yocto Project Reference Manual.
                    </para></listitem>
                <listitem><para>
                    For concepts on Yocto Project source repositories, see the
                    "<ulink url='&YOCTO_DOCS_REF_URL;#yocto-project-repositories'>Yocto Project Source Repositories</ulink>"
                    section in the Yocto Project Reference Manual."
                    </para></listitem>
            </itemizedlist>
        </note>
    </para>

    <section id='accessing-source-repositories'>
        <title>Accessing Source Repositories</title>

        <para>
            Yocto Project maintains upstream Git
            <ulink url='&YOCTO_DOCS_REF_URL;#source-repositories'>Source Repositories</ulink>
            that you can examine and access using a browser-based UI:
            <orderedlist>
                <listitem><para>
                    <emphasis>Access Repositories:</emphasis>
                    Open a browser and go to
                    <ulink url='&YOCTO_GIT_URL;'></ulink> to access the
                    GUI-based interface into the Yocto Project source
                    repositories.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Select a Repository:</emphasis>
                    Click on any repository in which you are interested (e.g.
                    <filename>poky</filename>).
                    </para></listitem>
                <listitem><para>
                    <emphasis>Find the URL Used to Clone the Repository:</emphasis>
                    At the bottom of the page, note the URL used to
                    <ulink url='&YOCTO_DOCS_REF_URL;#git-commands-clone'>clone</ulink>
                    that repository (e.g.
                    <filename>&YOCTO_GIT_URL;/poky</filename>).
                    </para></listitem>
                <listitem><para>
                    <emphasis>Examine Change History of the Repository:</emphasis>
                    At the top of the page, click on any branch in which you
                    might be interested (e.g.
                    <filename>&DISTRO_NAME_NO_CAP;</filename>).
                    You can then view the commit log or tree view for that
                    development branch.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='accessing-index-of-releases'>
        <title>Accessing Index of Releases</title>

        <para>
            Yocto Project maintains an Index of Releases area that contains
            related files that contribute to the Yocto Project.
            Rather than Git repositories, these files represent snapshot
            tarballs.
            <note><title>Tip</title>
                The recommended method for accessing Yocto Project
                components is to use Git to clone a repository and work from
                within that local repository.
                The procedure in this section exists should you desire a
                tarball snapshot of any given component.
            </note>
            <orderedlist>
                <listitem><para>
                    <emphasis>Access the Index of Releases:</emphasis>
                    Open a browser and go to
                    <ulink url='&YOCTO_DL_URL;/releases'></ulink> to access the
                    Index of Releases.
                    The list represents released components (e.g.
                    <filename>eclipse-plugin</filename>,
                    <filename>sato</filename>, and so on).
                    <note>
                        The <filename>yocto</filename> directory contains the
                        full array of released Poky tarballs.
                        The <filename>poky</filename> directory in the
                        Index of Releases was historically used for very
                        early releases and exists for retroactive
                        completeness only.
                    </note>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Select a Component:</emphasis>
                    Click on any released component in which you are interested
                    (e.g. <filename>yocto</filename>).
                    </para></listitem>
                <listitem><para>
                    <emphasis>Find the Tarball:</emphasis>
                    Drill down to find the associated tarball.
                    For example, click on <filename>yocto-2.3</filename> to
                    view files associated with the Yocto Project 2.3
                    release (e.g. <filename>poky-pyro-17.0.0tar.bz2</filename>,
                    which is the released Poky tarball).
                    </para></listitem>
                <listitem><para>
                    <emphasis>Download the Tarball:</emphasis>
                    Click a tarball to download and save a snapshot of a
                    given component.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='using-the-downloads-page'>
        <title>Using the Downloads Page</title>

        <para>
            The
            <ulink url='&YOCTO_HOME_URL;'>Yocto Project Website</ulink>
            uses a "Downloads" area from which you can locate and download
            tarballs of any Yocto Project release.
            Rather than Git repositories, these files represent snapshot
            tarballs.
            <note><title>Tip</title>
                The recommended method for accessing Yocto Project
                components is to use Git to clone a repository and work from
                within that local repository.
                The procedure in this section exists should you desire a
                tarball snapshot of any given component.
            </note>
            <orderedlist>
                <listitem><para>
                    <emphasis>Go to the Yocto Project Website:</emphasis>
                    Open The
                    <ulink url='&YOCTO_HOME_URL;'>Yocto Project Website</ulink>
                    in your browser.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Get to the Downloads Area:</emphasis>
                    Click the "Downloads" tab.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Select the Type of Files:</emphasis>
                    Click the type of files you want (i.e "Build System",
                    "Tools", or "Board Support Packages (BSPs)".
                    </para></listitem>
                <listitem><para>
                    <emphasis>Locate and Download the Tarball:</emphasis>
                    From the list of releases, locate the appropriate
                    download link and download the files.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='cloning-the-poky-repository'>
        <title>Cloning the <filename>poky</filename> Repository</title>

        <para>
            To use the Yocto Project, you need a release of the Yocto Project
            locally installed on your development system.
            The locally installed set of files is referred to as the
            <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
            in the Yocto Project documentation.
        </para>

        <para>
            You create your Source Directory by using
            <ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink> to clone a local
            copy of the upstream <filename>poky</filename> repository.
            <note><title>Tip</title>
                The preferred method of getting the Yocto Project Source
                Directory set up is to clone the repository.
            </note>
            Working from a copy of the upstream repository allows you
            to contribute back into the Yocto Project or simply work with
            the latest software on a development branch.
            Because Git maintains and creates an upstream repository with
            a complete history of changes and you are working with a local
            clone of that repository, you have access to all the Yocto
            Project development branches and tag names used in the upstream
            repository.
        </para>

        <para>
            Follow these steps to create a local version of the
            upstream
            <ulink url='&YOCTO_DOCS_REF_URL;#poky'><filename>poky</filename></ulink>
            Git repository.
            <orderedlist>
                <listitem><para>
                    <emphasis>Set Your Directory:</emphasis>
                    Be in the directory where you want to create your local
                    copy of poky.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Clone the Repository:</emphasis>
                    The following command clones the repository and uses
                    the default name "poky" for your local repository:
                    <literallayout class='monospaced'>
     $ git clone git://git.yoctoproject.org/poky
     Cloning into 'poky'...
     remote: Counting objects: 367178, done.
     remote: Compressing objects: 100% (88161/88161), done.
     remote: Total 367178 (delta 272761), reused 366942 (delta 272525)
     Receiving objects: 100% (367178/367178), 133.26 MiB | 6.40 MiB/s, done.
     Resolving deltas: 100% (272761/272761), done.
     Checking connectivity... done.
                    </literallayout>
                    Unless you specify a specific development branch or
                    tag name, Git clones the "master" branch, which results
                    in a snapshot of the latest development changes for
                    "master".</para>

                    <para>Once the repository is created, you can change to
                    that directory and check its status.
                    Here, the single "master" branch exists on your system
                    and by default, it is checked out:
                    <literallayout class='monospaced'>
     $ cd ~/poky
     $ git status
     On branch master
     Your branch is up-to-date with 'origin/master'.
     nothing to commit, working directory clean
     $ git branch
     * master
                    </literallayout>
                    Your local repository of poky is identical to the
                    upstream poky repository at the time from which it was
                    cloned.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='checking-out-by-branch-in-poky'>
        <title>Checking Out by Branch in Poky</title>

        <para>
            When you clone the upstream poky repository, you have access to
            all its development branches.
            Each development branch in a repository is unique as it forks
            off the "master" branch.
            To see and use the files of a particular development branch
            locally, you need to know the branch name and then specifically
            check out that development branch.
            <note>
                Checking out an active development branch by branch name
                gives you a snapshot of that particular branch at the time
                you check it out.
                Further development on top of the branch that occurs after
                check it out can occur.
            </note>
            <orderedlist>
                <listitem><para>
                    <emphasis>Switch to the Poky Directory:</emphasis>
                    If you have a local poky Git repository, switch to that
                    directory.
                    If you do not have the local copy of poky, see the
                    "<link linkend='cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</link>"
                    section.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Determine Existing Branch Names:</emphasis>
                    <literallayout class='monospaced'>
     $ git branch -a
     * master
       remotes/origin/1.1_M1
       remotes/origin/1.1_M2
       remotes/origin/1.1_M3
       remotes/origin/1.1_M4
       remotes/origin/1.2_M1
       remotes/origin/1.2_M2
       remotes/origin/1.2_M3
           .
           .
           .
       remotes/origin/master-next
       remotes/origin/master-next2
       remotes/origin/morty
       remotes/origin/pinky
       remotes/origin/purple
       remotes/origin/pyro
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Checkout the Branch:</emphasis>
                    Checkout the development branch in which you want to work.
                    For example, to access the files for the Yocto Project
                    2.3 Release (Pyro), use the following command:
                    <literallayout class='monospaced'>
     $ git checkout -b pyro origin/pyro
     Branch pyro set up to track remote branch pyro from origin.
     Switched to a new branch 'pyro'
                    </literallayout>
                    The previous command checks out the "pyro" development
                    branch and reports that the branch is tracking the upstream
                    "origin/pyro" branch.</para>

                    <para>The following command displays the branches
                    that are now part of your local poky repository.
                    The asterisk character indicates the branch that is
                    currently checked out for work:
                    <literallayout class='monospaced'>
     $ git branch
       master
     * pyro
                    </literallayout>
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='checkout-out-by-tag-in-poky'>
        <title>Checking Out by Tag in Poky</title>

        <para>
            Similar to branches, the upstream repository uses tags
            to mark specific commits associated with significant points in
            a development branch (i.e. a release point or stage of a
            release).
            You might want to set up a local branch based on one of those
            points in the repository.
            The process is similar to checking out by branch name except you
            use tag names.
            <note>
                Checking out a branch based on a tag gives you a
                stable set of files not affected by development on the
                branch above the tag.
            </note>
            <orderedlist>
                <listitem><para>
                    <emphasis>Switch to the Poky Directory:</emphasis>
                    If you have a local poky Git repository, switch to that
                    directory.
                    If you do not have the local copy of poky, see the
                    "<link linkend='cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</link>"
                    section.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Fetch the Tag Names:</emphasis>
                    To checkout the branch based on a tag name, you need to
                    fetch the upstream tags into your local repository:
                    <literallayout class='monospaced'>
     $ git fetch --tags
     $
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>List the Tag Names:</emphasis>
                    You can list the tag names now:
                    <literallayout class='monospaced'>
     $ git tag
     1.1_M1.final
     1.1_M1.rc1
     1.1_M1.rc2
     1.1_M2.final
     1.1_M2.rc1
        .
        .
        .
     yocto-2.2
     yocto-2.2.1
     yocto-2.3
     yocto_1.5_M5.rc8
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Checkout the Branch:</emphasis>
                    <literallayout class='monospaced'>
     $ git checkout tags/2.2_M2 -b my_yocto_2.2_M2
     Switched to a new branch 'my_yocto_2.2_M2'
     $ git branch
       master
     * my_yocto_2.2_M2
                    </literallayout>
                    The previous command creates and checks out a local
                    branch named "my_yocto_2.2_M2", which is based on
                    the commit in the upstream poky repository that has
                    the same tag.
                    In this example, the files you have available locally
                    as a result of the <filename>checkout</filename>
                    command are a snapshot of the
                    "morty" development branch at the point where
                    milestone two was reached.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>
</section>

<section id='performing-a-simple-build'>
    <title>Performing a Simple Build</title>

    <para>
        Several methods exist that allow you to build an image within the
        Yocto Project.
        This procedure shows how to build an image using BitBake from a
        Linux host.
        <note><title>Notes</title>
            <itemizedlist>
                <listitem><para>
                    For information on how to build an image using
                    <ulink url='&YOCTO_DOCS_REF_URL;#toaster-term'>Toaster</ulink>,
                    see the
                    <ulink url='&YOCTO_DOCS_TOAST_URL;'>Yocto Project Toaster Manual</ulink>.
                    </para></listitem>
                <listitem><para>
                    For information on how to use
                    <filename>devtool</filename> to build images, see the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'>Using <filename>devtool</filename> in Your SDK Workflow</ulink>"
                    section in the Yocto Project Software Development Kit
                    (SDK) Developer's Guide.
                    </para></listitem>
            </itemizedlist>
        </note>
    </para>

    <para>
        The build process creates an entire Linux distribution from source
        and places it in your
        <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
        under <filename>tmp/deploy/images</filename>.
        For detailed information on the build process using BitBake, see the
        "<ulink url='&YOCTO_DOCS_REF_URL;#images-dev-environment'>Images</ulink>"
        section in the Yocto Project Reference Manual.
        You can also reference the
        "<ulink url='&YOCTO_DOCS_QS_URL;#qs-building-images'>Building Images</ulink>"
        section in the Yocto Project Quick Start.
    </para>

    <para>
        The following figure and list overviews the build process:
        <imagedata fileref="figures/bitbake-build-flow.png" width="7in" depth="6in" align="center" scalefit="1" />
        <orderedlist>
            <listitem><para>
                <emphasis>Set Up Your Host Development System to Support
                Development Using the Yocto Project:</emphasis>
                See the
                "<ulink url='&YOCTO_DOCS_QS_URL;#the-linux-distro'>The Linux Distribution</ulink>"
                and the
                "<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>"
                sections both in the Yocto Project Quick Start for
                build host requirements.
                </para></listitem>
            <listitem><para>
                <emphasis>Set Up Your Source Directories:</emphasis>
                Make sure you have set up the Source Directory described in the
                "<link linkend='cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</link>"
                section.
                </para></listitem>
            <listitem><para>
                <emphasis>Initialize the Build Environment:</emphasis>
                Initialize the build environment by sourcing a build
                environment script (i.e.
                <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
                or
                <ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>).
                </para></listitem>
            <listitem><para>
                <emphasis>Make Sure Your <filename>local.conf</filename>
                File is Correct:</emphasis>
                Ensure the <filename>conf/local.conf</filename> configuration
                file, which is found in the
                <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
                is set up how you want it.
                This file defines many aspects of the build environment
                including the target machine architecture through the
                <filename><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'>MACHINE</ulink></filename> variable,
                the packaging format used during the build
                (<ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></ulink>),
                and a centralized tarball download directory through the
                <filename><ulink url='&YOCTO_DOCS_REF_URL;#var-DL_DIR'>DL_DIR</ulink></filename> variable.
                </para></listitem>
            <listitem><para>
                <emphasis>Build the Image:</emphasis>
                Build the image using the <filename>bitbake</filename> command.
                For example, the following command builds the
                <filename>core-image-minimal</filename> image:
                <literallayout class='monospaced'>
     $ bitbake core-image-minimal
                </literallayout>
                For information on BitBake, see the
                <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
                </para></listitem>
        </orderedlist>
    </para>
</section>

<section id='using-pre-built-binaries-and-qemu'>
    <title>Using Pre-Built Binaries and QEMU</title>

    <para>
        Another option you have to get started is to use pre-built binaries.
        The Yocto Project provides many types of binaries with each release.
        See the "<ulink url='&YOCTO_DOCS_REF_URL;#ref-images'>Images</ulink>"
        chapter in the Yocto Project Reference Manual
        for descriptions of the types of binaries that ship with a Yocto Project
        release.
    </para>

    <para>
        Using a pre-built binary is ideal for developing software
        applications to run on your target hardware.
        To do this, you need to be able to access the appropriate
        cross-toolchain tarball for the architecture on which you are
        developing.
        If you are using an SDK type image, the image ships with the complete
        toolchain native to the architecture (i.e. a toolchain designed to
        run on the
        <ulink url='&YOCTO_DOCS_REF_URL;#var-SDKMACHINE'><filename>SDKMACHINE</filename></ulink>).
        If you are not using an SDK type image, you need to separately download
        and install the stand-alone Yocto Project cross-toolchain tarball.
        See the
        "<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-appendix-obtain'>Obtaining the SDK</ulink>"
        appendix in the Yocto Project Software Development Kit (SDK)
        Developer's Guide for more information on locating and installing
        cross-toolchains.
    </para>

    <para>
        Regardless of the type of image you are using, you need to download the pre-built kernel
        that you will boot in the QEMU emulator and then download and extract the target root
        filesystem for your target machine’s architecture.
        You can get architecture-specific binaries and file systems from
        <ulink url='&YOCTO_MACHINES_DL_URL;'>machines</ulink>.
        You can get installation scripts for stand-alone toolchains from
        <ulink url='&YOCTO_TOOLCHAIN_DL_URL;'>toolchains</ulink>.
        Once you have all your files, you set up the environment to emulate the hardware
        by sourcing an environment setup script.
        Finally, you start the QEMU emulator.
        You can find details on all these steps in the
        <ulink url='&YOCTO_DOCS_SDK_URL;#sdk-manual'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>.
        You can learn more about using QEMU with the Yocto Project in the
        "<link linkend='dev-manual-qemu'>Using the Quick EMUlator (QEMU)</link>"
        section.
    </para>

    <para>
        Using QEMU to emulate your hardware can result in speed issues
        depending on the target and host architecture mix.
        For example, using the <filename>qemux86</filename> image in the emulator
        on an Intel-based 32-bit (x86) host machine is fast because the target and
        host architectures match.
        On the other hand, using the <filename>qemuarm</filename> image on the same Intel-based
        host can be slower.
        But, you still achieve faithful emulation of ARM-specific issues.
    </para>

    <para>
        To speed things up, the QEMU images support using <filename>distcc</filename>
        to call a cross-compiler outside the emulated system.
        If you used <filename>runqemu</filename> to start QEMU, and the
        <filename>distccd</filename> application is present on the host system, any
        BitBake cross-compiling toolchain available from the build system is automatically
        used from within QEMU simply by calling <filename>distcc</filename>.
        You can accomplish this by defining the cross-compiler variable
        (e.g. <filename>export CC="distcc"</filename>).
        Alternatively, if you are using a suitable SDK image or the appropriate
        stand-alone toolchain is present,
        the toolchain is also automatically used.
    </para>

    <note>
        Several mechanisms exist that let you connect to the system running on the
        QEMU emulator:
        <itemizedlist>
            <listitem><para>QEMU provides a framebuffer interface that makes standard
                consoles available.</para></listitem>
            <listitem><para>Generally, headless embedded devices have a serial port.
                If so, you can configure the operating system of the running image
                to use that port to run a console.
                The connection uses standard IP networking.</para></listitem>
            <listitem><para>
                SSH servers exist in some QEMU images.
                The <filename>core-image-sato</filename> QEMU image has a
                Dropbear secure shell (SSH) server that runs with the root
                password disabled.
                The <filename>core-image-full-cmdline</filename> and
                <filename>core-image-lsb</filename> QEMU images
                have OpenSSH instead of Dropbear.
                Including these SSH servers allow you to use standard
                <filename>ssh</filename> and <filename>scp</filename> commands.
                The <filename>core-image-minimal</filename> QEMU image,
                however, contains no SSH server.
                </para></listitem>
            <listitem><para>You can use a provided, user-space NFS server to boot the QEMU session
                using a local copy of the root filesystem on the host.
                In order to make this connection, you must extract a root filesystem tarball by using the
                <filename>runqemu-extract-sdk</filename> command.
                After running the command, you must then point the <filename>runqemu</filename>
                script to the extracted directory instead of a root filesystem image file.</para></listitem>
        </itemizedlist>
    </note>
</section>
</chapter>
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