path: root/documentation/toaster-manual/toaster-manual-setup-and-use.xml

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

<chapter id='toaster-manual-setup-and-use'>

<title>Setting Up and Using Toaster</title>

    <section id='starting-toaster-for-local-development'>
        <title>Starting Toaster for Local Development</title>

        <para>
            Once you have set up the Yocto Project and installed the
            Toaster system dependencies as described in the
            "<link linkend='toaster-manual-start'>Preparing to Use Toaster</link>"
            chapter, you are ready to start Toaster.
        </para>

        <para>
            Navigate to the root of your
            <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
            (e.g. <filename>poky</filename>):
            <literallayout class='monospaced'>
     $ cd poky
            </literallayout>
            Once in that directory, source the build environment script:
            <literallayout class='monospaced'>
     $ source oe-init-build-env
            </literallayout>
            Next, from the build directory (e.g.
            <filename>poky/build</filename>), start Toaster using this
            command:
            <literallayout class='monospaced'>
     $ source toaster start
            </literallayout>
            You can now run your builds from the command line, or with
            Toaster as explained in section
            "<link linkend='using-the-toaster-web-interface'>Using the Toaster Web Interface</link>".
        </para>

        <para>
            To access the Toaster web interface, open your favorite
            browser and enter the following:
            <literallayout class='monospaced'>
     http://127.0.0.1:8000
            </literallayout>
        </para>
    </section>

    <section id='setting-a-different-port'>
        <title>Setting a Different Port</title>

        <para>
            By default, Toaster starts on port 8000.
            You can use the <filename>WEBPORT</filename> parameter to
            set a different port.
            For example, the following command sets the port to "8400":
            <literallayout class='monospaced'>
     $ source toaster start webport=8400
            </literallayout>
        </para>
    </section>

    <section id='setting-up-external-access'>
        <title>Setting up External Access</title>

        <para>
            By default, Toaster binds to the loop back address
            (i.e. localhost), which does not allow access from
            external hosts. To allow external access, use the
            <filename>WEBPORT</filename> parameter to open an
            address that connects to the network, specifically the
            IP address that your NIC uses to connect to the network.
            You can also bind to all IP addresses the computer
            supports by using the shortcut
            "0.0.0.0:<replaceable>port</replaceable>".
        </para>

        <para>
            The following example binds to all IP addresses on the
            host:
            <literallayout class='monospaced'>
     $ source toaster start webport=0.0.0.0:8400
            </literallayout>
            This example binds to a specific IP address on the host's
            NIC:
            <literallayout class='monospaced'>
     $ source toaster start webport=192.168.1.1:8400
            </literallayout>
        </para>
    </section>

    <section id='the-directory-for-cloning-layers'>
        <title>The Directory for Cloning Layers</title>

        <para>
            Toaster creates a <filename>_toaster_clones</filename>
            directory inside your Source Directory
            (i.e. <filename>poky</filename>) to clone any layers
            needed for your builds.
        </para>

        <para>
            Alternatively, if you would like all of your Toaster related
            files and directories to be in a particular location other than
            the default, you can set the <filename>TOASTER_DIR</filename>
            environment variable, which takes precedence over your current
            working directory.
            Setting this environment variable causes Toaster to create and use
            <filename>$TOASTER_DIR./_toaster_clones</filename>.
        </para>
    </section>

    <section id='toaster-the-build-directory'>
        <title>The Build Directory</title>

        <para>
            Toaster creates a build directory within your Source
            Directory (e.g. <filename>poky</filename>) to execute
            the builds.
        </para>

        <para>
            Alternatively, if you would like all of your Toaster related files
            and directories to be in a particular location, you can set
            the <filename>TOASTER_DIR</filename> environment variable,
            which takes precedence over your current working directory.
            Setting this environment variable causes Toaster to use
            <filename>$TOASTER_DIR/build</filename> as the build directory.
        </para>
    </section>

    <section id='toaster-creating-a-django-super-user'>
        <title>Creating a Django Superuser</title>

        <para>
            Toaster is built on the
            <ulink url='https://www.djangoproject.com/'>Django framework</ulink>.
            Django provides an administration interface you can use
            to edit Toaster configuration parameters.
        </para>

        <para>
            To access the Django administration interface, you must
            create a superuser by following these steps:
            <orderedlist>
              <listitem><para>
                  If you used <filename>pip3</filename>, which is
                  recommended, to set up the Toaster system dependencies,
                  you need be sure the local user path is in your
                  <filename>PATH</filename> list.
                  To append the pip3 local user path, use the following
                  command:
                  <literallayout class='monospaced'>
   $ export PATH=$PATH:$HOME/.local/bin
                  </literallayout>
                  </para></listitem>
              <listitem><para>
                  From the directory containing the Toaster database,
                  which by default is the
                  <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
                  invoke the <filename>createsuperuser</filename> command
                  from <filename>manage.py</filename>:
                  <literallayout class='monospaced'>
   $ cd ~/poky/build
   $ ../bitbake/lib/toaster/manage.py createsuperuser
                  </literallayout>
                  </para></listitem>
              <listitem><para>
                  Django prompts you for the username, which you need to
                  provide.
                  </para></listitem>
              <listitem><para>
                  Django prompts you for an email address, which is
                  optional.
                  </para></listitem>
              <listitem><para>
                  Django prompts you for a password, which you must provide.
                  </para></listitem>
              <listitem><para>
                  Django prompts you to re-enter your password for verification.
                  </para></listitem>
          </orderedlist>
          After completing these steps, the following confirmation message
          appears:
          <literallayout class='monospaced'>
   Superuser created successfully.
          </literallayout>
      </para>

      <para>
          Creating a superuser allows you to access the Django administration
          interface through a browser.
          The URL for this interface is the same as the URL used for the
          Toaster instance with "/admin" on the end.
          For example, if you are running Toaster locally, use the
          following URL:
          <literallayout class='monospaced'>
   http://127.0.0.1:8000/admin
          </literallayout>
          You can use the Django administration interface to set Toaster
          configuration parameters such as the build directory, layer sources,
          default variable values, and BitBake versions.
      </para>
  </section>

  <section id='toaster-setting-up-a-production-instance-of-toaster'>
      <title>Setting Up a Production Instance of Toaster</title>

      <para>
          You can use a production instance of Toaster to share the
          Toaster instance with remote users, multiple users, or both.
          The production instance is also the setup that can handle
          heavier loads on the web service.
          Use the instructions in the following sections to set up
          Toaster to run builds through the Toaster web interface.
      </para>

      <section id='toaster-production-instance-requirements'>
          <title>Requirements</title>

          <para>
              Be sure you meet the following requirements:
              <note>
                  You must comply with all Apache,
                  <filename>mod-wsgi</filename>, and Mysql requirements.
              </note>
              <itemizedlist>
                  <listitem><para>
                      Have all the build requirements as described in the
                      "<link linkend='toaster-manual-start'>Preparing to Use Toaster</link>"
                      chapter.
                      </para></listitem>
                  <listitem><para>
                      Have an Apache webserver.
                      </para></listitem>
                  <listitem><para>
                      Have <filename>mod-wsgi</filename> for the Apache
                      webserver.
                      </para></listitem>
                  <listitem><para>
                      Use the Mysql database server.
                      </para></listitem>
                  <listitem><para>
                      If you are using Ubuntu 16.04, run the following:
                      <literallayout class='monospaced'>
   $ sudo apt-get install apache2 libapache2-mod-wsgi-py3 mysql-server python3-pip libmysqlclient-dev
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      If you are using Fedora 24 or a RedHat distribution, run
                      the following:
                      <literallayout class='monospaced'>
   $ sudo dnf install httpd python3-mod_wsgi python3-pip mariadb-server mariadb-devel python3-devel
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      If you are using openSUSE Leap 42.1, run
                      the following:
                      <literallayout class='monospaced'>
   $ sudo zypper install apache2 apache2-mod_wsgi-python3 python3-pip mariadb mariadb-client python3-devel
                      </literallayout>
                      </para></listitem>
              </itemizedlist>
          </para>
      </section>

      <section id='toaster-installation-steps'>
          <title>Installation</title>

          <para>
              Perform the following steps to install Toaster:
              <orderedlist>
                  <listitem><para>
                      Create toaster user and set its home directory to
                      <filename>/var/www/toaster</filename>:
                      <literallayout class='monospaced'>
    $ sudo /usr/sbin/useradd toaster -md /var/www/toaster -s /bin/false
    $ sudo su - toaster -s /bin/bash
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      Checkout a copy of <filename>poky</filename>
                      into the web server directory.
                      You will be using <filename>/var/www/toaster</filename>:
                      <literallayout class='monospaced'>
   $ git clone git://git.yoctoproject.org/poky
   $ git checkout &DISTRO_NAME_NO_CAP;
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      Install Toaster
                      dependencies using the --user flag which
                      keeps the Python packages
                      isolated from your system-provided packages:
                      <literallayout class='monospaced'>
   $ cd /var/www/toaster/
   $ pip3 install --user -r ./poky/bitbake/toaster-requirements.txt
   $ pip3 install --user mysqlclient
                      </literallayout>
                      <note>
                          Isolating these packages is not required but is
                          recommended.
                          Alternatively, you can use your operating system's
                          package manager to install the packages.
                      </note>
                      </para></listitem>
                  <listitem><para>
                      Configure Toaster by editing
                      <filename>/var/www/toaster/poky/bitbake/lib/toaster/toastermain/settings.py</filename>
                      as follows:
                      <itemizedlist>
                          <listitem><para>
                              Edit the
                              <ulink url='http://docs.djangoproject.com/en/1.8/ref/settings/#std:setting-SECRET_KEY'>DATABASE</ulink>
                              settings:
                              <literallayout class='monospaced'>
   DATABASES = {
       'default': {
           'ENGINE': 'django.db.backends.mysql',
           'NAME': 'toaster_data',
           'USER': 'toaster',
           'PASSWORD': 'yourpasswordhere',
           'HOST': 'localhost',
           'PORT': '3306',
      }
   }
                              </literallayout>
                              </para></listitem>
                          <listitem><para>
                              Edit the
                              <ulink url='http://docs.djangoproject.com/en/1.8/ref/settings/#std:setting-SECRET_KEY'>SECRET_KEY</ulink>:
                              <literallayout class='monospaced'>
   SECRET_KEY = '<replaceable>your_secret_key</replaceable>'
                              </literallayout>
                              </para></listitem>
                          <listitem><para>
                              Edit the
                              <ulink url='http://docs.djangoproject.com/en/1.8/ref/settings/#std:setting-SECRET_KEY'>STATIC_ROOT</ulink>:
                              <literallayout class='monospaced'>
   STATIC_ROOT = '/var/www/toaster/static_files/'
                              </literallayout>
                              </para></listitem>
                      </itemizedlist>
                      </para></listitem>
                  <listitem><para>
                      Add the database and user to the <filename>mysql</filename>
                      server defined earlier:
                      <literallayout class='monospaced'>
   $ mysql -u root -p
   mysql> CREATE DATABASE toaster_data;
   mysql> CREATE USER 'toaster'@'localhost' identified by 'yourpasswordhere';
   mysql> GRANT all on toaster_data.* to 'toaster'@'localhost';
   mysql> quit
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      Get Toaster to create the database schema,
                      default data, and gather the statically-served files:
                      <literallayout class='monospaced'>
   $ cd  /var/www/toaster/poky/
   $ ./bitbake/lib/toaster/manage.py migrate
   $ TOASTER_DIR=`pwd` TOASTER_CONF=./meta-poky/conf/toasterconf.json \
     ./bitbake/lib/toaster/manage.py checksettings
   $ ./bitbake/lib/toaster/manage.py collectstatic
                      </literallayout>
                      </para>

                      <para>
                          For the above set of commands, after moving to the
                          <filename>poky</filename> directory,
                          the <filename>migrate</filename>
                          command ensures the database
                          schema has had changes propagated correctly (i.e.
                          migrations).
                      </para>

                      <para>
                          The next line sets the Toaster root directory
                          <filename>TOASTER_DIR</filename> and the location of
                          the Toaster configuration file
                          <filename>TOASTER_CONF</filename>, which is
                          relative to the Toaster root directory
                          <filename>TOASTER_DIR</filename>.
                          For more information on the Toaster configuration file,
                          see the
                          <link linkend='configuring-toaster'>Configuring Toaster</link>
                          chapter.
                      </para>

                      <para>
                          This line also runs the <filename>checksettings</filename>
                          command, which configures the location of the Toaster
                          <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build directory</ulink>.
                          The Toaster root directory <filename>TOASTER_DIR</filename>
                          determines where the Toaster build directory
                          is created on the file system.
                          In the example above,
                          <filename>TOASTER_DIR</filename> is set as follows:
                          <literallayout class="monospaced">
   /var/www/toaster/poky
                          </literallayout>
                          This setting causes the Toaster build directory to be:
                          <literallayout class="monospaced">
   /var/www/toaster/poky/build
                          </literallayout>
                      </para>

                      <para>
                          Finally, the <filename>collectstatic</filename> command
                          is a Django framework command that collects all the
                          statically served files into a designated directory to
                          be served up by the Apache web server as defined by
                          <filename>STATIC_ROOT</filename>.
                      </para></listitem>
                  <listitem><para>
                      Add an Apache configuration file for Toaster to your Apache web
                      server's configuration directory.
                      If you are using Ubuntu or Debian, put the file here:
                      <literallayout class='monospaced'>
   /etc/apache2/conf-available/toaster.conf
                      </literallayout>
                      If you are using Fedora or RedHat, put it here:
                      <literallayout class='monospaced'>
   /etc/httpd/conf.d/toaster.conf
                      </literallayout>
                      If you are using OpenSUSE, put it here:
                      <literallayout class='monospaced'>
   /etc/apache2/conf.d/toaster.conf
                      </literallayout>
                      Following is a sample Apache configuration for Toaster
                      you can follow:
                      <literallayout class='monospaced'>
   Alias /static /var/www/toaster/static_files
   &lt;Directory /var/www/toaster/static_files&gt;
           &lt;IfModule mod_access_compat.c&gt;
                   Order allow,deny
                   Allow from all
           &lt;/IfModule&gt;
           &lt;IfModule !mod_access_compat.c&gt;
                   Require all granted
           &lt;/IfModule&gt;
   &lt;/Directory&gt;

   &lt;Directory /var/www/toaster/poky/bitbake/lib/toaster/toastermain&gt;
           &lt;Files "wsgi.py"&gt;
              Require all granted
           &lt;/Files&gt;
   &lt;/Directory&gt;

   WSGIDaemonProcess toaster_wsgi python-path=/var/www/toaster/poky/bitbake/lib/toaster:/var/www/toaster/.local/lib/python3.4/site-packages

   WSGIScriptAlias / "/var/www/toaster/poky/bitbake/lib/toaster/toastermain/wsgi.py"
   &lt;Location /&gt;
       WSGIProcessGroup toaster_wsgi
   &lt;/Location&gt;
                      </literallayout>
                      If you are using Ubuntu or Debian,
                      you will need to enable the config and module for Apache:
                      <literallayout class='monospaced'>
   $ sudo a2enmod wsgi
   $ sudo a2enconf toaster
   $ chmod +x bitbake/lib/toaster/toastermain/wsgi.py
                      </literallayout>
                      Finally, restart Apache to make sure all new configuration
                      is loaded.
                      For Ubuntu, Debian, and OpenSUSE use:
                      <literallayout class='monospaced'>
   $ sudo service apache2 restart
                      </literallayout>
                      For Fedora and RedHat use:
                      <literallayout class='monospaced'>
   $ sudo service httpd restart
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      Prepare the systemd service to run Toaster builds.
                      Here is a sample configuration file for the service:
                      <literallayout class='monospaced'>
   [Unit]
   Description=Toaster runbuilds

   [Service]
   Type=forking
   User=toaster
   ExecStart=/usr/bin/screen -d -m -S runbuilds /var/www/toaster/poky/bitbake/lib/toaster/runbuilds-service.sh start
   ExecStop=/usr/bin/screen -S runbuilds -X quit
   WorkingDirectory=/var/www/toaster/poky

   [Install]
   WantedBy=multi-user.target
                      </literallayout>
                      Prepare the <filename>runbuilds-service.sh</filename>
                      script that you need to place in the
                      <filename>/var/www/toaster/poky/bitbake/lib/toaster/</filename>
                      directory by setting up executable permissions:
                      <literallayout class='monospaced'>
   #!/bin/bash

   #export http_proxy=http://proxy.host.com:8080
   #export https_proxy=http://proxy.host.com:8080
   #export GIT_PROXY_COMMAND=$HOME/bin/gitproxy

   cd ~/poky/
   source ./oe-init-build-env build
   source ../bitbake/bin/toaster $1 noweb
   [ "$1" == 'start' ] &amp;&amp; /bin/bash
                      </literallayout>
                      </para></listitem>
                  <listitem><para>
                      Run the service:
                      <literallayout class='monospaced'>
   # service runbuilds start
                      </literallayout>
                      Since the service is running in a detached screen
                      session, you can attach to it using this command:
                      <literallayout class='monospaced'>
   $ sudo su - toaster
   $ screen -rS runbuilds
                      </literallayout>
                      You can detach from the service again using "Ctrl-a"
                      followed by "d" key combination.
                      </para></listitem>
              </orderedlist>
              You can now open up a browser and start using Toaster.
          </para>
      </section>
  </section>

  <section id='using-the-toaster-web-interface'>
      <title>Using the Toaster Web Interface</title>

      <para>
          The Toaster web interface allows you to do the following:
          <itemizedlist>
              <listitem><para>
                  Browse published layers in the
                  <ulink url='http://layers.openembedded.org'>OpenEmbedded Layer Index</ulink>
                  that are available for your selected version of the build
                  system.
                  </para></listitem>
              <listitem><para>
                  Import your own layers for building.
                  </para></listitem>
              <listitem><para>
                  Add and remove layers from your configuration.
                  </para></listitem>
              <listitem><para>
                  Set configuration variables.
                  </para></listitem>
              <listitem><para>
                  Select a target or multiple targets to build.
                  </para></listitem>
              <listitem><para>
                  Start your builds.
                  </para></listitem>
              <listitem><para>
                  See what was built (recipes and packages) and what
                  packages were installed into your final image.
                  </para></listitem>
              <listitem><para>
                  Browse the directory structure of your image.
                  </para></listitem>
              <listitem><para>
                  See the value of all variables in your build configuration,
                  and which files set each value.
                  </para></listitem>
              <listitem><para>
                  Examine error, warning and trace messages to aid in
                  debugging.
                  </para></listitem>
              <listitem><para>
                  See information about the BitBake tasks executed and
                  reused during your build, including those that used
                  shared state.
                  </para></listitem>
              <listitem><para>
                  See dependency relationships between recipes, packages
                  and tasks.
                  </para></listitem>
              <listitem><para>
                  See performance information such as build time, task time,
                  CPU usage, and disk I/O.
                  </para></listitem>
          </itemizedlist>
      </para>

      <section id='web-interface-videos'>
          <title>Toaster Web Interface Videos</title>

          <para>
              Following are several videos that show how to use the Toaster GUI:
              <itemizedlist>
                  <listitem><para><emphasis>Build Configuration:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=qYgDZ8YzV6w'>video</ulink>
                      overviews and demonstrates build configuration for Toaster.
                      </para></listitem>
                  <listitem><para><emphasis>Build Custom Layers:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=QJzaE_XjX5c'>video</ulink>
                      shows you how to build custom layers that are used with
                      Toaster.
                      </para></listitem>
                  <listitem><para><emphasis>Toaster Homepage and Table Controls:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=QEARDnrR1Xw'>video</ulink>
                      goes over the Toaster entry page, and provides
                      an overview of the data manipulation capabilities of
                      Toaster, which include search, sorting and filtering by
                      different criteria.
                      </para></listitem>
                  <listitem><para><emphasis>Build Dashboard:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=KKqHYcnp2gE'>video</ulink>
                      shows you the build dashboard, a page providing an
                      overview of the information available for a selected build.
                      </para></listitem>
                  <listitem><para><emphasis>Image Information:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=XqYGFsmA0Rw'>video</ulink>
                      walks through the information Toaster provides
                      about images: packages installed and root file system.
                      </para></listitem>
                  <listitem><para><emphasis>Configuration:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=UW-j-T2TzIg'>video</ulink>
                      provides Toaster build configuration information.
                      </para></listitem>
                  <listitem><para><emphasis>Tasks:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=D4-9vGSxQtw'>video</ulink>
                      shows the information Toaster provides about the
                      tasks run by the build system.
                      </para></listitem>
                  <listitem><para><emphasis>Recipes and Packages Built:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=x-6dx4huNnw'>video</ulink>
                      shows the information Toaster provides about recipes
                      and packages built.
                      </para></listitem>
                  <listitem><para><emphasis>Performance Data:</emphasis>
                      This
                      <ulink url='https://www.youtube.com/watch?v=qWGMrJoqusQ'>video</ulink>
                      shows the build performance data provided by
                      Toaster.
                      </para></listitem>
              </itemizedlist>
          </para>
      </section>

      <section id='a-note-on-the-local-yocto-project-release'>
          <title>Additional Information About the Local Yocto Project Release</title>

          <para>
              This section only applies if you have set up Toaster
              for local development, as explained in the
              "<link linkend='starting-toaster-for-local-development'>Starting Toaster for Local Development</link>"
              section.
          </para>

          <para>
              When you create a project in Toaster, you will be asked to
              provide a name and to select a Yocto Project release.
              One of the release options you will find is called
              "Local Yocto Project".
              <imagedata fileref="figures/new-project.png" align="center" width="9in" />
          </para>

          <para>
              When you select the "Local Yocto Project" release, Toaster
              will run your builds using the local Yocto
              Project clone you have in your computer: the same clone
              you are using to run Toaster.
              Unless you manually update
              this clone, your builds will always use the same Git revision.
          </para>

          <para>
              If you select any of the other release options, Toaster
              will fetch the tip of your selected release from the upstream
              <ulink url='https://git.yoctoproject.org'>Yocto Project repository</ulink>
              every time you run a build.
              Fetching this tip effectively
              means that if your selected release is updated upstream, the
              Git revision you are using for your builds will change.
              If you are doing development locally, you might not want this
              change to happen.
              In that case, the "Local Yocto Project"
              release might be the right choice.
          </para>

          <para>
              However, the "Local Yocto Project" release
              will not provide you with any compatible layers, other than the
              three core layers that come with the Yocto Project:
              <itemizedlist>
                  <listitem><para>
                      <ulink url='http://layers.openembedded.org/layerindex/branch/master/layer/openembedded-core/'>openembedded-core</ulink>
                  </para></listitem>
                  <listitem><para>
                      <ulink url='http://layers.openembedded.org/layerindex/branch/master/layer/meta-poky/'>meta-poky</ulink>
                  </para></listitem>
                  <listitem><para>
                      <ulink url='http://layers.openembedded.org/layerindex/branch/master/layer/meta-yocto-bsp/'>meta-yocto-bsp</ulink>
                  </para></listitem>
              </itemizedlist>
              <imagedata fileref="figures/compatible-layers.png" align="center" width="9in" />
          </para>

          <para>
              If you want to build any other layers, you will need to
              manually import them into your Toaster project, using the
              "Import layer" page.
              <imagedata fileref="figures/import-layer.png" align="center" width="9in" />
          </para>

      </section>

      <section id='toaster-web-interface-preferred-version'>
          <title>Building a Specific Recipe Given Multiple Versions</title>

            <para>
                Occasionally, a layer might provide more than one version of
                the same recipe.
                For example, the <filename>openembedded-core</filename> layer
                provides two versions of the <filename>bash</filename> recipe
                (i.e. 3.2.48 and 4.3.30-r0) and two versions of the
                <filename>which</filename> recipe (i.e. 2.21 and 2.18).
                The following figure shows this exact scenario:
                <imagedata fileref="figures/bash-oecore.png" align="center" width="9in" depth="6in" />
            </para>

            <para>
                By default, the OpenEmbedded build system builds one of the
                two recipes.
                For the <filename>bash</filename> case, version 4.3.30-r0 is
                built by default.
                Unfortunately, Toaster as it exists, is not able to override
                the default recipe version.
                If you would like to build bash 3.2.48, you need to set the
                <ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></ulink>
                variable.
                You can do so from Toaster, using the "Add variable" form,
                which is available in the "BitBake variables" page of the
                project configuration section as shown in the following screen:
                <imagedata fileref="figures/add-variable.png" align="center" width="9in" depth="6in" />
            </para>

            <para>
                To specify <filename>bash</filename> 3.2.48 as the version to build,
                enter "PREFERRED_VERSION_bash" in the "Variable" field, and "3.2.48"
                in the "Value" field.
                Next, click the "Add variable" button:
                <imagedata fileref="figures/set-variable.png" align="center" width="9in" depth="6in" />
            </para>

            <para>
                After clicking the "Add variable" button, the settings for
                <filename>PREFERRED_VERSION</filename> are added to the bottom
                of the BitBake variables list.
                With these settings, the OpenEmbedded build system builds the
                desired version of the recipe rather than the default version:
                <imagedata fileref="figures/variable-added.png" align="center" width="9in" depth="6in" />
            </para>
        </section>
    </section>
</chapter>