user-manual-execution.xml: Draft of "Execution" chapter

This is a rough draft of the chapter.  Major sections are in
place.  We need to scrub content now.

Seems like the discussion of BBFILES fit better in this
execution flow chapter.  So, I moved it above the parsing
section.

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>

2 files changed, 702 insertions, 765 deletions

diff --git a/doc/user-manual/user-manual-bitbakecommand.xml b/doc/user-manual/user-manual-bitbakecommand.xml
index e895c6b3f..5c301a56f 100644
--- a/doc/user-manual/user-manual-bitbakecommand.xml
+++ b/doc/user-manual/user-manual-bitbakecommand.xml
@@ -4,17 +4,22 @@
 <chapter id="user-manual-command">
     <title>The BitBake Command</title>
 
-    <section id='bitbake-command-introduction'>
-        <title>Introduction</title>
-
-        <para>
-            Bitbake is the primary command in the system.
-            It facilitates executing tasks in a single <filename>.bb</filename>
-            file, or executing a given task on a set of multiple
-            <filename>.bb</filename> files, accounting for interdependencies
-            amongst them.
-        </para>
-    </section>
+    <para>
+        BitBake is the underlying piece of the build system.
+        Two excellent examples are the Yocto Project and the OpenEmbedded
+        build systems.
+        Each provide an environment in which to develop embedded Linux
+        images, and each use BitBake as their underlying build engine.
+    </para>
+
+    <para>
+        BitBake facilitates executing tasks in a single <filename>.bb</filename>
+        file, or executing a given task on a set of multiple
+        <filename>.bb</filename> files, accounting for interdependencies
+        amongst them.
+        This chapter presents the BitBake syntax, provides some execution
+        examples, and shows you how to control BitBake with key metadata.
+    </para>
 
     <section id='usage-and-syntax'>
         <title>Usage and syntax</title>
@@ -110,7 +115,9 @@ Options:
             <para>
                 Executing tasks for a single recipe file is relatively simple.
                 You specify the file in question, and BitBake parses
-                it and executes the specified task (or “build” by default).
+                it and executes the specified task.
+                If you do not specify a task, BitBake executes the default
+                task, which is "build”.
                 BitBake obeys inter-task dependencies when doing
                 so.
             </para>
@@ -138,38 +145,36 @@ Options:
                 when one wants to manage multiple <filename>.bb</filename>
                 files.
                 Clearly there needs to be a way to tell BitBake what
-                files are available, and of those, which we
-                want to execute at this time.
-                There also needs to be a way for each <filename>.bb</filename>
+                files are available, and of those, which you
+                want to execute.
+                There also needs to be a way for each recipe
                 to express its dependencies, both for build-time and
                 runtime.
-                There must be a way for the user to express their preferences
+                There must be a way for you to express recipe preferences
                 when multiple recipes provide the same functionality, or when
-                there are multiple versions of a  <filename>.bb</filename> file.
-            </para>
-
-            <para>
-                The next section, Metadata, outlines how to specify such things.
+                there are multiple versions of a  recipe.
             </para>
 
             <para>
                 The <filename>bitbake</filename> command, when not using
-                "--buildfile", accepts a PROVIDER, not a filename or
-                anything else.
-                By default, a <filename>.bb</filename> generally PROVIDES its
-                packagename, packagename-version, and packagename-version-revision.
+                "--buildfile" or "-b" only accepts a "PROVIDER".
+                You cannot provide anything else.
+                By default, a recipe file generally "PROVIDES" its
+                "packagename", "packagename-version", and
+                "packagename-version-revision" as shown in the following
+                example:
                 <literallayout class='monospaced'>
      $ bitbake foo
 
      $ bitbake foo-1.0
 
      $ bitbake foo-1.0-r0
-
+                </literallayout>
+                This next example "PROVIDES" the package name and also uses
+                the "-c" option to tell BitBake to just excute the
+                <filename>do_clean</filename> task:
+                <literallayout class='monospaced'>
      $ bitbake -c clean foo
-
-     $ bitbake virtual/whatever
-
-     $ bitbake -c clean virtual/whatever
                 </literallayout>
             </para>
         </section>
@@ -180,88 +185,57 @@ Options:
             <para>
                 BitBake is able to generate dependency graphs using
                 the dot syntax.
-                These graphs can be converted to images using the dot
+                You can convert these graphs into images using the dot
                 application from
                 <ulink url='http://www.graphviz.org'>Graphviz</ulink>.
-                Two files will be written into the current working directory:
-                <filename>depends.dot</filename> containing dependency information
-                at the package level and <filename>task-depends.dot</filename>
-                containing a breakdown of the dependencies at the task level.
-                To stop depending on common depends, one can use the "-I" depend
-                option to omit these from the graph.
-                This can lead to more readable graphs.
-                This way, <filename>DEPENDS</filename> from inherited classes
-                such as <filename>base.bbclass</filename> can be removed from the
-                graph.
-                <literallayout class='monospaced'>
-     $ bitbake -g foo
-
-     $ bitbake -g -I virtual/whatever -I bloom foo
-                </literallayout>
             </para>
-        </section>
-    </section>
-
-    <section id='special-variables'>
-        <title>Special Variables</title>
-
-        <para>
-            Certain variables affect BitBake operation:
-        </para>
-
-        <section id='bb-number-threads'>
-            <title><filename>BB_NUMBER_THREADS</filename></title>
 
             <para>
-                The number of threads BitBake should run at once (default: 1).
+                When you generate a dependency graph, BitBake writes two files
+                to the current working directory:
+                <filename>depends.dot</filename>, which contains dependency information
+                at the package level, and <filename>task-depends.dot</filename>,
+                which contains a breakdown of the dependencies at the task level.
             </para>
-        </section>
-    </section>
-
-    <section id='bitbake-command-metadata'>
-        <title>Metadata</title>
 
-        <para>
-            As you may have seen in the usage information, or in the
-            information about <filename>.bb</filename> files, the
-            <filename>BBFILES</filename> variable is how the BitBake
-            tool locates its files.
-            This variable is a space-separated list of files
-            that are available, and supports wildcards.
-        </para>
-
-        <section id='setting-bbfiles'>
-            <title>Setting <filename>BBFILES</filename></title>
+            <para>
+                To stop depending on common depends, use use the "-I" depend
+                option and BitBake omits them from the graph.
+                Leaving this information out can produce more readable graphs.
+                This way, you can remove from the graph
+                <filename>DEPENDS</filename> from inherited classes
+                such as <filename>base.bbclass</filename>.
+            </para>
 
             <para>
+                Here are two exmples that create dependency graphs.
+                The second example omits common depends from the graph:
                 <literallayout class='monospaced'>
-     BBFILES = "/path/to/bbfiles/*.bb"
+     $ bitbake -g foo
+
+     $ bitbake -g -I virtual/whatever -I bloom foo
                 </literallayout>
-                With regard to dependencies, it expects the
-                <filename>.bb</filename> to define a
-                <filename>DEPENDS</filename> variable, which contains a
-                space separated list of “package names”, which themselves
-                are the <filename>PN</filename> variable. The
-                <filename>PN</filename> variable is, in general,
-                set to a component of the <filename>.bb</filename>
-                filename by default.
             </para>
         </section>
+    </section>
 
-        <section id='depending-on-another-recipe-file'>
-            <title>Depending on Another Recipe File</title>
-
-            <para>
-                <literallayout class='monospaced'>
-     a.bb:
+    <section id='controlling-bitbake'>
+        <title>Controlling BitBake</title>
 
-     PN = "package-a"
-     DEPENDS += "package-b"
+        <para>
+            Including variables in your recipe and class files help control
+            how BitBake operates.
+        </para>
 
-     b.bb:
+        <section id='execution-threads'>
+            <title>Execution Threads</title>
 
-     PN = "package-b"
-                </literallayout>
+            <para>
+                You can control how many thread BitBake supports by using the
+                <link linkend='var-BB_NUMBER_THREADS'><filename>BB_NUMBER_THREADS</filename></link>
+                variable.
+                You would set this in your <filename>local.conf</filename>
+                configuration file.
             </para>
         </section>
 
diff --git a/doc/user-manual/user-manual-execution.xml b/doc/user-manual/user-manual-execution.xml
index 365392dbf..aa345de69 100644
--- a/doc/user-manual/user-manual-execution.xml
+++ b/doc/user-manual/user-manual-execution.xml
@@ -5,686 +5,649 @@
     <title>Execution</title>
 
     <para>
-        Tasks can either be a shell task or a Python task.
-        For shell tasks, BitBake writes a shell script to
-        <filename>${WORKDIR}/temp/run.do_taskname.pid</filename>
-        and then executes the script.
-        The generated shell script contains all the exported variables,
-        and the shell functions with all variables expanded.
-        Output from the shell script goes to the file
-        <filename>${WORKDIR}/temp/log.do_taskname.pid</filename>.
-        Looking at the expanded shell functions in the run file and
-        the output in the log files is a useful debugging technique.
+        The primary purpose for running BitBake is to produce an
+        image, which can be a kernel or a software development kit (SDK).
+        Of course, you can execute the <filename>bitbake</filename>
+        command with options that cause it to execute single tasks,
+        compile single recipe files, capture or clear data, or simply
+        return information about the execution environment.
     </para>
 
     <para>
-        For Python tasks, BitBake executes the task internally and logs
-        information to the controlling terminal.
-        Future versions of BitBake will write the functions to files
-        similar to the way shell tasks are handled.
-        Logging will be handled in a way similar to shell tasks as well.
+        This chapter describes BitBake's execution process from start
+        to finish when you use it to create an image.
+        The execution process is launched using the following command
+        form:
+        <literallayout class='monospaced'>
+     $ bitbake &lt;target&gt;
+        </literallayout>
+        For information on the BitBake command and its options,
+        see the
+        "<link linkend='user-manual-command'>BitBake Command</link>
+        chapter.
     </para>
 
-    <para>
-        Once all the tasks have been completed BitBake exits.
-    </para>
+    <section id='parsing-the-base-configuration-metadata'>
+        <title>Parsing the Base Configuration Metadata</title>
+
+        <para>
+            The first thing BitBake does is parse base configuration
+            metadata.
+            Base configuration metadata consists of the
+            <filename>bblayers.conf</filename> file to determine what
+            layers BitBake needs to recognize, all necessary
+            <filename>layer.conf</filename> files (one from each layer),
+            and <filename>bitbake.conf</filename>.
+        </para>
+
+        <para>
+            The <filename>bitbake.conf</filename> file resides in the
+            <filename>conf</filename> directory, which must be listed in
+            <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
+            This configuratoin file lists and includes other configuration
+            files from the <filename>conf</filename> directory below the
+            directories listed in <filename>BBPATH</filename>.
+            In general, the most important of these included
+            configuration files from a user's perspective
+            is <filename>local.conf</filename>, which contains the user's
+            customized settings for the build environment.
+        </para>
+
+        <para>
+            Other notable configuration files are the distribution configuration
+            file and the machine configuration file.
+            These configuration files are normally identified by
+            variables unique to the build systems using BitBake.
+            For example, the Yocto Project uses the
+            <filename>DISTRO</filename> and <filename>MACHINE</filename>
+            variables, respectively.
+        </para>
+
+        <para>
+            Prior to parsing configuration files, Bitbake looks
+            at certain variables, including:
+            <itemizedlist>
+                <listitem><para><link linkend='var-BB_ENV_WHITELIST'><filename>BB_ENV_WHITELIST</filename></link></para></listitem>
+                <listitem><para><link linkend='var-BB_PRESERVE_ENV'><filename>BB_PRESERVE_ENV</filename></link></para></listitem>
+                <listitem><para><link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link></para></listitem>
+                <listitem><para><link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link></para></listitem>
+                <listitem><para><link linkend='var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></link></para></listitem>
+                <listitem><para><link linkend='var-PREFERRED_PROVIDERS'><filename>PREFERRED_PROVIDERS</filename></link></para></listitem>
+            </itemizedlist>
+        </para>
+
+        <para>
+            The base configuration metadata is global
+            and therefore affects all packages and tasks that are executed.
+        </para>
+
+        <para>
+            BitBake first searches the current working directory for an
+            optional <filename>conf/bblayers.conf</filename> configuration file.
+            This file is expected to contain a
+            <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link>
+            variable that is a space delimited list of 'layer' directories.
+        </para>
+
+        <para>
+            For each directory (layer) in this list, a <filename>conf/layer.conf</filename>
+            file is searched for and parsed with the
+            <link linkend='var-LAYERDIR'><filename>LAYERDIR</filename></link>
+            variable being set to the directory where the layer was found.
+            The idea is these files automatically setup
+            <link linkend='var-BBPATH'><filename>BBPATH</filename></link>
+            and other variables correctly for a given build directory.
+        </para>
+
+        <para>
+            BitBake then expects to find the <filename>conf/bitbake.conf</filename>
+            file somewhere in the user-specified <filename>BBPATH</filename>.
+            That configuration file generally has include directives to pull
+            in any other metadata such as files specific to the architecture,
+            the machine, the local environment, and so forth.
+        </para>
+
+        <para>
+            Only variable definitions and include directives are allowed
+            in <filename>.conf</filename> files.
+            The following variables include:
+            <itemizedlist>
+                <listitem><para>
+                    <link linkend='var-BITBAKE_UI'><filename>BITBAKE_UI</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BBDEBUG'><filename>BBDEBUG</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-MULTI_PROVIDER_WHITELIST'><filename>MULTI_PROVIDER_WHITELIST</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <filename>BBPKGS</filename>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BB_DEFAULT_TASK'><filename>BB_DEFAULT_TASK</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BB_VERBOSE_LOGS'><filename>BB_VERBOSE_LOGS</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BB_NICE_LEVEL'><filename>BB_NICE_LEVEL</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BBFILE_COLLECTIONS'><filename>BBFILE_COLLECTIONS</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BB_DANGLINGAPPENDS_WARNONLY'><filename>BB_DANGLINGAPPENDS_WARNONLY</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BBINCLUDED'><filename>BBINCLUDED</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BBFILE_PRIORITY'><filename>BBFILE_PRIORITY</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BUILDNAME'><filename>BUILDNAME</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BBMASK'><filename>BBMASK</filename></link>
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+
+        <para>
+            After parsing configuration files, BitBake uses its rudimentary
+            inheritance mechanism, which is through class files, to inherit
+            some standard classes.
+            BitBake parses a class when the inherit directive responsible
+            for getting that class is encountered.
+        </para>
+
+        <para>
+            The <filename>base.bbclass</filename> file is always included.
+            Other classes that are specified in the configuration using the
+            <link linkend='var-INHERIT'><filename>INHERIT</filename></link>
+            variable are also included.
+            BitBake searches for class files in a "classes" subdirectory under
+            the paths in <filename>BBPATH</filename> in the same way as
+            configuration files.
+        </para>
+
+        <para>
+            A good way to get an idea of the configuration files and
+            the class files used in your execution environment is to
+            run the following BitBake command:
+            <literallayout class='monospaced'>
+     $ bitbake -e > mybb.log
+            </literallayout>
+            Examining the top of the <filename>mybb.log</filename>
+            shows you the many configuration files and class files
+            used in your execution environment.
+        </para>
+    </section>
+
+    <section id='locating-recipes'>
+        <title>Locating Recipes</title>
+
+        <para>
+            The <filename>BBFILES</filename> variable is how BitBake
+            locates files.
+            This variable is a space-separated list of files
+            that are available, supports wildcards, and is set shortly
+            after the parsing phase of BitBake's execution.
+        </para>
+
+        <para>
+            <literallayout class='monospaced'>
+     BBFILES = "/path/to/bbfiles/*.bb"
+            </literallayout>
+            With regard to dependencies, it expects the
+            <filename>.bb</filename> to define a
+            <filename>DEPENDS</filename> variable, which contains a
+           space separated list of “package names”, which themselves
+            are the <filename>PN</filename> variable. The
+            <filename>PN</filename> variable is, in general,
+            set to a component of the <filename>.bb</filename>
+           filename by default.
+        </para>
+   </section>
+
+    <section id='parsing-recipes'>
+        <title>Parsing Recipes</title>
+
+        <para>
+            After classes are included, the variable
+            <filename>BBFILES</filename> is set, usually in
+            <filename>local.conf</filename>, and defines the list of
+            places to search for recipe and append files.
+            Adding extra content to <filename>BBFILES</filename> is best
+            achieved through the use of BitBake layers.
+        </para>
+
+        <para>
+            BitBake parses each recipe and append file located with
+            <filename>BBFILES</filename> and stores the values of various
+            variables into the datastore.
+            In summary, for each recipe and append file pairing, the configuration
+            plus the base class of variables are set, followed by the data in the
+            recipe file itself, followed by any inherit commands
+            that the recipe file might contain.
+        </para>
+
+        <para>
+            Part of parsing a recipe is making sure that all the recipes
+            that the recipe being parsed depends on are understood.
+            These other recipes could be located in other layers or in
+            a specific layer version.
+            These two variables in a recipe can help with with these
+            cases:
+            <itemizedlist>
+                <listitem><para>
+                    <link linkend='var-LAYERDEPENDS'><filename>LAYERDEPENDS</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-LAYERVERSION'><filename>LAYERVERSION</filename></link>
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+
+        <para>
+            Because parsing recipe and append files is a time consuming
+            process, a cache, referred to as the "setscene"
+            is kept to speed up subsequent parsing.
+            The setscene is invalid if the timestamps of a recipe changes,
+            any of the include files change, configuration files change,
+            or class files on which the recipe file depends change.
+        </para>
+    </section>
+
+    <section id='executing-tasks'>
+        <title>Executing Tasks</title>
+
+        <para>
+            Tasks can either be a shell task or a Python task.
+            For shell tasks, BitBake writes a shell script to
+            <filename>${WORKDIR}/temp/run.do_taskname.pid</filename>
+            and then executes the script.
+            The generated shell script contains all the exported variables,
+            and the shell functions with all variables expanded.
+            Output from the shell script goes to the file
+            <filename>${WORKDIR}/temp/log.do_taskname.pid</filename>.
+            Looking at the expanded shell functions in the run file and
+            the output in the log files is a useful debugging technique.
+        </para>
+
+        <para>
+            For Python tasks, BitBake executes the task internally and logs
+            information to the controlling terminal.
+            Future versions of BitBake will write the functions to files
+            similar to the way shell tasks are handled.
+            Logging will be handled in a way similar to shell tasks as well.
+        </para>
+
+        <para>
+            Variables specific to scheduling functionality exist:
+            <itemizedlist>
+                <listitem><para>
+                    <link linkend='var-BB_SCHEDULER'><filename>BB_SCHEDULER</filename></link>
+                    </para></listitem>
+                <listitem><para>
+                    <link linkend='var-BB_SCHEDULERS'><filename>BB_SCHEDULERS</filename></link>
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+    </section>
+
+    <section id='source-fetching-dev-environment'>
+        <title>Source Fetching</title>
+
+        <para>
+            The first stages of building a recipe are to fetch and unpack
+            the source code:
+            <imagedata fileref="figures/source-fetching.png" align="center" width="6.5in" depth="5in" />
+        </para>
+
+        <para>
+            The <filename>do_fetch</filename> and
+            <filename>do_unpack</filename> tasks fetch the source files
+            and unpack them into the work directory.
+            By default, everything is accomplished in the
+            build directory,
+            which has a defined structure.
+        </para>
+
+        <para>
+            Unpacked source files are pointed to by a variable.
+            For example, in the Yocto Project and OpenEmbedded build systems,
+            the <filename>S</filename> variable points to these source files.
+            Each recipe has an area in the Build Directory where the
+            unpacked source code resides.
+            The name of that directory for any given recipe is defined from
+            several different variables.
+            You can see the variables that define these directories
+            by looking at the figure that shows the structure and variables
+            used in the Yocto Project:
+            <itemizedlist>
+                <listitem><para><filename>TMPDIR</filename>
+                    </para></listitem>
+                <listitem><para><filename>PACKAGE_ARCH</filename>
+                    </para></listitem>
+                <listitem><para><filename>TARGET_OS</filename>
+                    </para></listitem>
+                <listitem><para><link linkend='var-PN'><filename>PN</filename></link>
+                    </para></listitem>
+                <listitem><para><link linkend='var-PV'><filename>PV</filename></link>
+                    </para></listitem>
+                <listitem><para><link linkend='var-PR'><filename>PR</filename></link>
+                    </para></listitem>
+                <listitem><para><filename>WORKDIR</filename>
+                    </para></listitem>
+                <listitem><para><filename>S</filename>
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+
+        <para>
+            Briefly, the <filename>S</filename> directory contains the
+            unpacked source files for a recipe.
+            The <filename>WORKDIR</filename> directory is where all the
+            building goes on for a given recipe.
+        </para>
+    </section>
+
+    <section id='patching-dev-environment'>
+        <title>Patching</title>
+
+        <para>
+            Once source code is fetched and unpacked, BitBake locates
+            patch files and applies them to the source files:
+            <imagedata fileref="figures/patching.png" align="center" width="6in" depth="5in" />
+        </para>
+
+        <para>
+            The <filename>do_patch</filename> task processes recipes by
+            using the
+            <link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>
+            variable to locate applicable patch files, which by default
+            are <filename>*.patch</filename> or
+            <filename>*.diff</filename> files, or any file if
+            "apply=yes" is specified for the file in
+            <filename>SRC_URI</filename>.
+        </para>
 
-    <section id='parsing-and-execution'>
-        <title>Parsing and Execution</title>
-
-        <section id='parsing-overview'>
-            <title>Parsing Overview</title>
-
-            <para>
-                BitBake parses configuration files, classes, recipes, and append
-                files.
-            </para>
-
-            <para>
-                The first thing BitBake does is look for the
-                <filename>bitbake.conf</filename> file.
-                This file resides in the <filename>conf</filename>
-                directory, which must be listed in
-                <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
-            </para>
-
-            <para>
-                The <filename>bitbake.conf</filename> file lists other configuration
-                files to include from the <filename>conf</filename> directory below the
-                directories listed in <filename>BBPATH</filename>.
-                In general, the most important of these
-                configuration files from a user's perspective
-                is <filename>local.conf</filename>, which contains the user's
-                customized settings for the build environment.
-            </para>
-
-            <para>
-                Other notable configuration files are the distribution configuration
-                file and the machine configuration file.
-                These configuration files are normally identified by
-                variables unique to the build systems using BitBake.
-                For example, the Yocto Project uses the
-                <filename>DISTRO</filename> and <filename>MACHINE</filename>
-                variables, respectively.
-            </para>
-
-            <para>
-                After parsing of the configuration files, some standard classes are
-                included.
-                The <filename>base.bbclass</filename> file
-                is always included.
-                Other classes that are specified in the configuration using the
-                <link linkend='var-INHERIT'><filename>INHERIT</filename></link>
-                variable are also included.
-                BitBake searches for class files in a "classes" subdirectory under
-                the paths in <filename>BBPATH</filename> in the same way as
-                configuration files.
-            </para>
-
-            <para>
-                After classes are included, the variable
-                <filename>BBFILES</filename> is set, usually in
-                <filename>local.conf</filename>, and defines the list of
-                places to search for recipe and append files.
-                Adding extra content to <filename>BBFILES</filename> is best
-                achieved through the use of BitBake layers.
-            </para>
-
-            <para>
-                BitBake parses each recipe and append file located with
-                <filename>BBFILES</filename> and stores the values of various
-                variables into the datastore.
-                In summary, for each recipe and append file pairing, the configuration
-                plus the base class of variables are set, followed by the data in the
-                recipe file itself, followed by any inherit commands
-                that the recipe file might contain.
-            </para>
-
-            <para>
-                Because parsing recipe and append files is a time consuming
-                process, a cache, referred to as the "setscene"
-                is kept to speed up subsequent parsing.
-                The setscene is invalid if the timestamps of a recipe changes,
-                any of the include files change, configuration files change,
-                or class files on which the recipe file depends change.
-            </para>
-        </section>
-
-        <section id='parsing-configuration-files'>
-            <title>Configuration files</title>
-
-            <para>
-                Prior to parsing configuration files, Bitbake looks
-                at certain variables, including:
-                <itemizedlist>
-                    <listitem><para><link linkend='var-BB_ENV_WHITELIST'><filename>BB_ENV_WHITELIST</filename></link></para></listitem>
-                    <listitem><para><link linkend='var-BB_PRESERVE_ENV'><filename>BB_PRESERVE_ENV</filename></link></para></listitem>
-                    <listitem><para><link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link></para></listitem>
-                    <listitem><para><link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link></para></listitem>
-                    <listitem><para><link linkend='var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></link></para></listitem>
-                    <listitem><para><link linkend='var-PREFERRED_PROVIDERS'><filename>PREFERRED_PROVIDERS</filename></link></para></listitem>
-                </itemizedlist>
-            </para>
-
-            <para>
-                The first kind of metadata in BitBake is configuration metadata.
-                This metadata is global, and therefore affects all packages and
-                tasks that are executed.
-            </para>
-
-            <para>
-                BitBake will first search the current working directory for an
-                optional <filename>conf/bblayers.conf</filename> configuration file.
-                This file is expected to contain a
-                <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link>
-                variable that is a space delimited list of 'layer' directories.
-                For each directory in this list, a <filename>conf/layer.conf</filename>
-                file will be searched for and parsed with the
-                <link linkend='var-LAYERDIR'><filename>LAYERDIR</filename></link>
-                variable being set to the directory where the layer was found.
-                The idea is these files will setup
-                <link linkend='var-BBPATH'><filename>BBPATH</filename></link>
-                and other variables correctly for a given build directory automatically
-                for the user.
-            </para>
-
-            <para>
-                BitBake will then expect to find <filename>conf/bitbake.conf</filename>
-                file somewhere in the user specified <filename>BBPATH</filename>.
-                That configuration file generally has include directives to pull
-                in any other metadata (generally files specific to architecture,
-                machine, local and so on).
-            </para>
-
-            <para>
-                Only variable definitions and include directives are allowed
-                in <filename>.conf</filename> files.
-                The following variables include:
-                <itemizedlist>
-                    <listitem><para>
-                        <link linkend='var-BITBAKE_UI'><filename>BITBAKE_UI</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BBDEBUG'><filename>BBDEBUG</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-MULTI_PROVIDER_WHITELIST'><filename>MULTI_PROVIDER_WHITELIST</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <filename>BBPKGS</filename>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BB_DEFAULT_TASK'><filename>BB_DEFAULT_TASK</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-TOPDIR'><filename>TOPDIR</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BB_VERBOSE_LOGS'><filename>BB_VERBOSE_LOGS</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BB_NICE_LEVEL'><filename>BB_NICE_LEVEL</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BBFILE_COLLECTIONS'><filename>BBFILE_COLLECTIONS</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BB_DANGLINGAPPENDS_WARNONLY'><filename>BB_DANGLINGAPPENDS_WARNONLY</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BBINCLUDED'><filename>BBINCLUDED</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BBFILE_PRIORITY'><filename>BBFILE_PRIORITY</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BUILDNAME'><filename>BUILDNAME</filename></link>
-                        </para></listitem>
-                    <listitem><para>
-                        <link linkend='var-BBMASK'><filename>BBMASK</filename></link>
-                        </para></listitem>
-                </itemizedlist>
-            </para>
-
-            <section id='layers'>
-                <title>Layers</title>
-
-                <para>
-                    Layers allow you to isolate different types of
-                    customizations from each other.
-                    While you might find it tempting to keep everything in one layer
-                    when working on a single project, the more modular you organize
-                    your metadata, the easier it is to cope with future changes.
-                </para>
-
-                <para>
-                    To illustrate how you can use layers to keep things modular,
-                    consider machine customizations.
-                    These types of customizations typically reside in a special layer,
-                    rather than a general layer, called a Board Specific Package (BSP) Layer.
-                    Furthermore, the machine customizations should be isolated from
-                    recipes and metadata that support a new GUI environment, for
-                    example.
-                    This situation gives you a couple of layers: one for the machine
-                    configurations and one for the GUI environment.
-                    It is important to understand, however, that the BSP layer can still
-                    make machine-specific additions to recipes within
-                    the GUI environment layer without polluting the GUI layer itself
-                    with those machine-specific changes.
-                    You can accomplish this through a recipe that is a BitBake append
-                    (<filename>.bbappend</filename>) file.
-                </para>
-
-                <para>
-                    There are certain variables specific to layers:
-                    <itemizedlist>
-                        <listitem><para>
-                            <link linkend='var-LAYERDEPENDS'><filename>LAYERDEPENDS</filename></link>
-                            </para></listitem>
-                        <listitem><para>
-                            <link linkend='var-LAYERVERSION'><filename>LAYERVERSION</filename></link>
-                            </para></listitem>
-                    </itemizedlist>
-                </para>
-            </section>
-
-            <section id='schedulers'>
-                <title>Schedulers</title>
-
-                <para>
-                    Variables specific to scheduling functionality exist:
-                    <itemizedlist>
-                        <listitem><para>
-                            <link linkend='var-BB_SCHEDULER'><filename>BB_SCHEDULER</filename></link>
-                            </para></listitem>
-                        <listitem><para>
-                            <link linkend='var-BB_SCHEDULERS'><filename>BB_SCHEDULERS</filename></link>
-                            </para></listitem>
-                    </itemizedlist>
-                </para>
-            </section>
-        </section>
-
-        <section id='metadata-classes'>
-            <title>Classes</title>
-
-            <para>
-                BitBake's rudimentary inheritance mechanism is accomplished using
-                classes.
-                As briefly mentioned in the metadata introduction, BitBake
-                parses a class when an inherit directive is encountered, and it
-                is located in the <filename>classes</filename> directory
-                relative to the directories in
-                <link linkend='var-BBPATH'><filename>BBPATH</filename></link>.
-            </para>
-        </section>
-
-        <section id='recipe-bb-files'>
-            <title>Recipe (<filename>.bb</filename>) Files</title>
-
-            <para>
-                Recipe files, which are files that have the
-                <filename>.bb</filename> file extension, are logical units of
-                tasks for execution.
-                Normally, that logical unit is a package that needs to be
-                built.
-            </para>
-
-            <para>
-                BitBake obeys all inter-recipe dependencies.
-            </para>
-
-            <para>
-                Recipe files must reside in locations found in the
-                <link linkend='var-BBFILES'><filename>BBFILES</filename></link>
-                variable.
-            </para>
-        </section>
-
-        <section id='append-bbappend-files'>
-            <title>Append (<filename>.bbappend</filename>) Files</title>
-
-            <para>
-                Append files, which are files that have the
-                <filename>.bbappend</filename> file extension, add or
-                extend build information to an existing
-                <link linkend='recipe-bb-files'>recipe file</link>.
-            </para>
-
-            <para>
-                BitBake expects every append file to have a corresponding recipe file.
-                Furthermore, the append file and corresponding recipe file
-                must use the same root filename.
-                The filenames can differ only in the file type suffix used
-                (e.g. <filename>formfactor_0.0.bb</filename> and
-                <filename>formfactor_0.0.bbappend</filename>).
-            </para>
-
-            <para>
-                Information in append files overrides the information in the
-                similarly-named recipe file.
-            </para>
-        </section>
+        <para>
+            BitBake finds and applies multiple patches for a single recipe
+            in the order in which it finds the patches.
+            Patches are applied to the recipe's source files located in the
+            <filename>S</filename> directory.
+        </para>
+
+        <para>
+            For more information on how the source directories are
+            created, see the
+            "<link linkend='source-fetching-dev-environment'>Source Fetching</link>"
+            section.
+        </para>
     </section>
 
-    <section id='bitbake-dev-environment'>
-        <title>BitBake</title>
-
-        <para>
-            The OpenEmbedded build system uses BitBake to produce images.
-            BitBake consists of several functional areas.
-            This section takes a closer look at each of those areas.
-        </para>
-
-        <section id='source-fetching-dev-environment'>
-            <title>Source Fetching</title>
-
-            <para>
-                The first stages of building a recipe are to fetch and unpack
-                the source code:
-                <imagedata fileref="figures/source-fetching.png" align="center" width="6.5in" depth="5in" />
-            </para>
-figures/
-            <para>
-                The <filename>do_fetch</filename> and
-                <filename>do_unpack</filename> tasks fetch the source files
-                and unpack them into the work directory.
-                By default, everything is accomplished in the
-                build directory,
-                which has a defined structure.
-            </para>
-
-            <para>
-                Unpacked source files are pointed to by a variable.
-                For example, in the Yocto Project and OpenEmbedded build systems,
-                the <filename>S</filename> variable points to these source files.
-                Each recipe has an area in the Build Directory where the
-                unpacked source code resides.
-                The name of that directory for any given recipe is defined from
-                several different variables.
-                You can see the variables that define these directories
-                by looking at the figure that shows the structure and variables
-                used in the Yocto Project:
-                <itemizedlist>
-                    <listitem><para><filename>TMPDIR</filename>
-                        </para></listitem>
-                    <listitem><para><filename>PACKAGE_ARCH</filename>
-                        </para></listitem>
-                    <listitem><para><filename>TARGET_OS</filename>
-                        </para></listitem>
-                    <listitem><para><link linkend='var-PN'><filename>PN</filename></link>
-                        </para></listitem>
-                    <listitem><para><link linkend='var-PV'><filename>PV</filename></link>
-                        </para></listitem>
-                    <listitem><para><link linkend='var-PR'><filename>PR</filename></link>
-                        </para></listitem>
-                    <listitem><para><filename>WORKDIR</filename>
-                        </para></listitem>
-                    <listitem><para><filename>S</filename>
-                        </para></listitem>
-                </itemizedlist>
-            </para>
-
-            <para>
-                Briefly, the <filename>S</filename> directory contains the
-                unpacked source files for a recipe.
-                The <filename>WORKDIR</filename> directory is where all the
-                building goes on for a given recipe.
-            </para>
-        </section>
-
-        <section id='patching-dev-environment'>
-            <title>Patching</title>
-
-            <para>
-                Once source code is fetched and unpacked, BitBake locates
-                patch files and applies them to the source files:
-                <imagedata fileref="figures/patching.png" align="center" width="6in" depth="5in" />
-            </para>
-
-            <para>
-                The <filename>do_patch</filename> task processes recipes by
-                using the
-                <link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>
-                variable to locate applicable patch files, which by default
-                are <filename>*.patch</filename> or
-                <filename>*.diff</filename> files, or any file if
-                "apply=yes" is specified for the file in
-                <filename>SRC_URI</filename>.
-            </para>
-
-            <para>
-                BitBake finds and applies multiple patches for a single recipe
-                in the order in which it finds the patches.
-                Patches are applied to the recipe's source files located in the
-                <filename>S</filename> directory.
-            </para>
-
-            <para>
-                For more information on how the source directories are
-                created, see the
-                "<link linkend='source-fetching-dev-environment'>Source Fetching</link>"
-                section.
-            </para>
-        </section>
-
-        <section id='configuration-and-compilation-dev-environment'>
-            <title>Configuration and Compilation</title>
-
-            <para>
-                After source code is patched, BitBake executes tasks that
-                configure and compile the source code:
-                <imagedata fileref="figures/configuration-compile-autoreconf.png" align="center" width="7in" depth="5in" />
-            </para>
-
-            <para>
-                This step in the build process consists of three tasks:
-                <itemizedlist>
-                    <listitem><para><emphasis><filename>do_configure</filename>:</emphasis>
-                        This task configures the source by enabling and
-                        disabling any build-time and configuration options for
-                        the software being built.
-                        Configurations can come from the recipe itself as well
-                        as from an inherited class.
-                        Additionally, the software itself might configure itself
-                        depending on the target for which it is being built.
-                        </para>
-
-                        <para>The configurations handled by the
-                        <filename>do_configure</filename> task are specific
-                        to source code configuration for the source code
-                        being built by the recipe.</para>
-
-                        <para>If you are using the Autotools class
-                        (<filename>autotools.bbclass</filename>),
-                        you can add additional configuration options by using
-                        the <filename>EXTRA_OECONF</filename>
-                        variable.
-                        For information on how this variable works within
-                        that class, see the
-                        <filename>meta/classes/autotools.bbclass</filename> file.
-                        </para></listitem>
-                    <listitem><para><emphasis><filename>do_compile</filename>:</emphasis>
-                        Once a configuration task has been satisfied, BitBake
-                        compiles the source using the
-                        <filename>do_compile</filename> task.
-                        Compilation occurs in the directory pointed to by the
-                        <link linkend='var-B'><filename>B</filename></link>
-                        variable.
-                        Realize that the <filename>B</filename> directory is, by
-                        default, the same as the
-                        <filename>S</filename>
-                        directory.</para></listitem>
-                    <listitem><para><emphasis><filename>do_install</filename>:</emphasis>
-                        Once compilation is done, BitBake executes the
-                        <filename>do_install</filename> task.
-                        This task copies files from the <filename>B</filename>
-                        directory and places them in a holding area pointed to
-                        by the <filename>D</filename> variable.</para></listitem>
-                </itemizedlist>
-            </para>
-        </section>
-
-        <section id='package-splitting-dev-environment'>
-            <title>Package Splitting</title>
-
-            <para>
-                After source code is configured and compiled, the
-                OpenEmbedded build system analyzes
-                the results and splits the output into packages:
-                <imagedata fileref="figures/analysis-for-package-splitting.png" align="center" width="7in" depth="7in" />
-            </para>
-
-            <para>
-                The <filename>do_package</filename> and
-                <filename>do_packagedata</filename> tasks combine to analyze
-                the files found in the <filename>D</filename> directory
-                and split them into subsets based on available packages and
-                files.
-                The analyzing process involves the following as well as other
-                items: splitting out debugging symbols,
-                looking at shared library dependencies between packages,
-                and looking at package relationships.
-                The <filename>do_packagedata</filename> task creates package
-                metadata based on the analysis such that the
-                OpenEmbedded build system can generate the final packages.
-                Working, staged, and intermediate results of the analysis
-                and package splitting process use these areas:
-                <itemizedlist>
-                    <listitem><para><filename>PKGD</filename>
-                        </para></listitem>
-                    <listitem><para><filename>PKGDATA_DIR</filename>
-                        </para></listitem>
-                    <listitem><para><filename>PKGDESTWORK</filename>
-                        </para></listitem>
-                    <listitem><para><filename>PKGDEST</filename>
-                        </para></listitem>
-                </itemizedlist>
-                The <filename>FILES</filename>
-                variable defines the files that go into each package in
-                <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>.
-                If you want details on how this is accomplished in the Yocto Project
-                for example, you can look at the <filename>package.bbclass</filename>
-                file in a Yocto tree.
-            </para>
-
-            <para>
-                Depending on the type of packages being created (RPM, DEB, or
-                IPK), the <filename>do_package_write_*</filename> task
-                creates the actual packages and places them in the
-                Package Feed area, which is
-                <filename>${TMPDIR}/deploy</filename>.
-                <note>
-                    Support for creating feeds directly from the
-                    <filename>deploy/*</filename> directories does not exist.
-                    Creating such feeds usually requires some kind of feed
-                    maintenance mechanism that would upload the new packages
-                    into an official package feed (e.g. the
-                    Ångström distribution).
-                    This functionality is highly distribution-specific
-                    and thus is not provided out of the box.
-                </note>
-            </para>
-        </section>
-
-        <section id='image-generation-dev-environment'>
-            <title>Image Generation</title>
-
-            <para>
-                Once packages are split and stored in the Package Feeds area,
-                the OpenEmbedded build system uses BitBake to generate the
-                root filesystem image:
-                <imagedata fileref="figures/image-generation.png" align="center" width="6in" depth="7in" />
-            </para>
-
-            <para>
-                The image generation process consists of several stages and
-                depends on many variables.
-                The <filename>do_rootfs</filename> task uses these key variables
-                to help create the list of packages to actually install:
-                <itemizedlist>
-                    <listitem><para><filename>IMAGE_INSTALL</filename>:
-                        Lists out the base set of packages to install from
-                        the Package Feeds area.</para></listitem>
-                    <listitem><para><filename>PACKAGE_EXCLUDE</filename>:
-                        Specifies packages that should not be installed.
-                        </para></listitem>
-                    <listitem><para><filename>IMAGE_FEATURES</filename>:
-                        Specifies features to include in the image.
-                        Most of these features map to additional packages for
-                        installation.</para></listitem>
-                    <listitem><para><filename>PACKAGE_CLASSES</filename>:
-                        Specifies the package backend to use and consequently
-                        helps determine where to locate packages within the
-                        Package Feeds area.</para></listitem>
-                    <listitem><para><filename>IMAGE_LINGUAS</filename>:
-                        Determines the language(s) for which additional
-                        language support packages are installed.
-                        </para></listitem>
-                </itemizedlist>
-            </para>
-
-            <para>
-                Package installation is under control of the package manager
-                (e.g. smart/rpm, opkg, or apt/dpkg) regardless of whether or
-                not package management is enabled for the target.
-                At the end of the process, if package management is not
-                enabled for the target, the package manager's data files
-                are deleted from the root filesystem.
-            </para>
-
-            <para>
-                During image generation, the build system attempts to run
-                all post-installation scripts.
-                Any that fail to run on the build host are run on the
-                target when the target system is first booted.
-                If you are using a
-                read-only root filesystem,
-                all the post installation scripts must succeed during the
-                package installation phase since the root filesystem cannot be
-                written into.
-            </para>
-
-            <para>
-                During Optimization, optimizing processes are run across
-                the image.
-                These processes include <filename>mklibs</filename> and
-                <filename>prelink</filename>.
-                The <filename>mklibs</filename> process optimizes the size
-                of the libraries.
-                A <filename>prelink</filename> process optimizes the dynamic
-                linking of shared libraries to reduce start up time of
-                executables.
-            </para>
-
-            <para>
-                Part of the image generation process includes compressing the
-                root filesystem image.
-                Compression is accomplished through several optimization
-                routines designed to reduce the overall size of the image.
-            </para>
-
-            <para>
-                After the root filesystem has been constructed, the image
-                generation process turns everything into an image file or
-                a set of image files.
-                The formats used for the root filesystem depend on the
-                <filename>IMAGE_FSTYPES</filename> variable.
-            </para>
+    <section id='configuration-and-compilation-dev-environment'>
+        <title>Configuration and Compilation</title>
 
+        <para>
+            After source code is patched, BitBake executes tasks that
+            configure and compile the source code:
+            <imagedata fileref="figures/configuration-compile-autoreconf.png" align="center" width="7in" depth="5in" />
+        </para>
+
+        <para>
+            This step in the build process consists of three tasks:
+            <itemizedlist>
+                <listitem><para><emphasis><filename>do_configure</filename>:</emphasis>
+                    This task configures the source by enabling and
+                    disabling any build-time and configuration options for
+                    the software being built.
+                    Configurations can come from the recipe itself as well
+                    as from an inherited class.
+                    Additionally, the software itself might configure itself
+                    depending on the target for which it is being built.
+                    </para>
+
+                    <para>The configurations handled by the
+                    <filename>do_configure</filename> task are specific
+                    to source code configuration for the source code
+                    being built by the recipe.</para>
+
+                    <para>If you are using the Autotools class
+                    (<filename>autotools.bbclass</filename>),
+                    you can add additional configuration options by using
+                    the <filename>EXTRA_OECONF</filename>
+                    variable.
+                    For information on how this variable works within
+                    that class, see the
+                    <filename>meta/classes/autotools.bbclass</filename> file.
+                    </para></listitem>
+                <listitem><para><emphasis><filename>do_compile</filename>:</emphasis>
+                    Once a configuration task has been satisfied, BitBake
+                    compiles the source using the
+                    <filename>do_compile</filename> task.
+                    Compilation occurs in the directory pointed to by the
+                    <link linkend='var-B'><filename>B</filename></link>
+                    variable.
+                    Realize that the <filename>B</filename> directory is, by
+                    default, the same as the
+                    <filename>S</filename>
+                    directory.</para></listitem>
+                <listitem><para><emphasis><filename>do_install</filename>:</emphasis>
+                    Once compilation is done, BitBake executes the
+                    <filename>do_install</filename> task.
+                    This task copies files from the <filename>B</filename>
+                    directory and places them in a holding area pointed to
+                    by the <filename>D</filename> variable.</para></listitem>
+            </itemizedlist>
+        </para>
+    </section>
+
+    <section id='package-splitting-dev-environment'>
+        <title>Package Splitting</title>
+
+        <para>
+            After source code is configured and compiled, the
+            OpenEmbedded build system analyzes
+            the results and splits the output into packages:
+            <imagedata fileref="figures/analysis-for-package-splitting.png" align="center" width="7in" depth="7in" />
+        </para>
+
+        <para>
+            The <filename>do_package</filename> and
+            <filename>do_packagedata</filename> tasks combine to analyze
+            the files found in the <filename>D</filename> directory
+            and split them into subsets based on available packages and
+            files.
+            The analyzing process involves the following as well as other
+            items: splitting out debugging symbols,
+            looking at shared library dependencies between packages,
+            and looking at package relationships.
+            The <filename>do_packagedata</filename> task creates package
+            metadata based on the analysis such that the
+            OpenEmbedded build system can generate the final packages.
+            Working, staged, and intermediate results of the analysis
+            and package splitting process use these areas:
+            <itemizedlist>
+                <listitem><para><filename>PKGD</filename>
+                    </para></listitem>
+                <listitem><para><filename>PKGDATA_DIR</filename>
+                    </para></listitem>
+                <listitem><para><filename>PKGDESTWORK</filename>
+                    </para></listitem>
+                <listitem><para><filename>PKGDEST</filename>
+                    </para></listitem>
+            </itemizedlist>
+            The <filename>FILES</filename>
+            variable defines the files that go into each package in
+            <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>.
+            If you want details on how this is accomplished in the Yocto Project
+            for example, you can look at the <filename>package.bbclass</filename>
+            file in a Yocto tree.
+        </para>
+
+        <para>
+            Depending on the type of packages being created (RPM, DEB, or
+            IPK), the <filename>do_package_write_*</filename> task
+            creates the actual packages and places them in the
+            Package Feed area, which is
+            <filename>${TMPDIR}/deploy</filename>.
             <note>
-                The entire image generation process is run under Pseudo.
-                Running under Pseudo ensures that the files in the root
-                filesystem have correct ownership.
+                Support for creating feeds directly from the
+                <filename>deploy/*</filename> directories does not exist.
+                Creating such feeds usually requires some kind of feed
+                maintenance mechanism that would upload the new packages
+                into an official package feed (e.g. the
+                Ångström distribution).
+                This functionality is highly distribution-specific
+                and thus is not provided out of the box.
             </note>
-        </section>
-
-        <section id='sdk-generation-dev-environment'>
-            <title>SDK Generation</title>
-
-            <para>
-                The OpenEmbedded build system uses BitBake to generate the
-                Software Development Kit (SDK) installer script:
-                <imagedata fileref="figures/sdk-generation.png" align="center" width="6in" depth="7in" />
-            </para>
-
-            <para>
-                Like image generation, the SDK script process consists of
-                several stages and depends on many variables.
-                The <filename>do_populate_sdk</filename> task uses these
-                key variables to help create the list of packages to actually
-                install.
-            </para>
-
-            <para>
-                The <filename>do_populate_sdk</filename> task handles two
-                parts: a target part and a host part.
-                The target part is the part built for the target hardware and
-                includes libraries and headers.
-                The host part is the part of the SDK that runs on the
-                <filename>SDKMACHINE</filename>.
-            </para>
-
-            <para>
-                Once both parts are constructed, the
-                <filename>do_populate_sdk</filename> task performs some cleanup
-                on both parts.
-                After the cleanup, the task creates a cross-development
-                environment setup script and any configuration files that
-                might be needed.
-            </para>
-
-            <para>
-                The final output of the task is the Cross-development
-                toolchain installation script (<filename>.sh</filename> file),
-                which includes the environment setup script.
-            </para>
-        </section>
+        </para>
+    </section>
+
+    <section id='image-generation-dev-environment'>
+        <title>Image Generation</title>
+
+        <para>
+            Once packages are split and stored in the Package Feeds area,
+            the OpenEmbedded build system uses BitBake to generate the
+            root filesystem image:
+            <imagedata fileref="figures/image-generation.png" align="center" width="6in" depth="7in" />
+        </para>
+
+        <para>
+            The image generation process consists of several stages and
+            depends on many variables.
+            The <filename>do_rootfs</filename> task uses these key variables
+            to help create the list of packages to actually install:
+            <itemizedlist>
+                <listitem><para><filename>IMAGE_INSTALL</filename>:
+                    Lists out the base set of packages to install from
+                    the Package Feeds area.</para></listitem>
+                <listitem><para><filename>PACKAGE_EXCLUDE</filename>:
+                    Specifies packages that should not be installed.
+                    </para></listitem>
+                <listitem><para><filename>IMAGE_FEATURES</filename>:
+                    Specifies features to include in the image.
+                    Most of these features map to additional packages for
+                    installation.</para></listitem>
+                <listitem><para><filename>PACKAGE_CLASSES</filename>:
+                    Specifies the package backend to use and consequently
+                    helps determine where to locate packages within the
+                    Package Feeds area.</para></listitem>
+                <listitem><para><filename>IMAGE_LINGUAS</filename>:
+                    Determines the language(s) for which additional
+                    language support packages are installed.
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+
+        <para>
+            Package installation is under control of the package manager
+            (e.g. smart/rpm, opkg, or apt/dpkg) regardless of whether or
+            not package management is enabled for the target.
+            At the end of the process, if package management is not
+            enabled for the target, the package manager's data files
+            are deleted from the root filesystem.
+        </para>
+
+        <para>
+            During image generation, the build system attempts to run
+            all post-installation scripts.
+            Any that fail to run on the build host are run on the
+            target when the target system is first booted.
+            If you are using a
+            read-only root filesystem,
+            all the post installation scripts must succeed during the
+            package installation phase since the root filesystem cannot be
+            written into.
+        </para>
+
+        <para>
+            During Optimization, optimizing processes are run across
+            the image.
+            These processes include <filename>mklibs</filename> and
+            <filename>prelink</filename>.
+            The <filename>mklibs</filename> process optimizes the size
+            of the libraries.
+            A <filename>prelink</filename> process optimizes the dynamic
+            linking of shared libraries to reduce start up time of
+            executables.
+        </para>
+
+        <para>
+            Part of the image generation process includes compressing the
+            root filesystem image.
+            Compression is accomplished through several optimization
+            routines designed to reduce the overall size of the image.
+        </para>
+
+        <para>
+            After the root filesystem has been constructed, the image
+            generation process turns everything into an image file or
+            a set of image files.
+            The formats used for the root filesystem depend on the
+            <filename>IMAGE_FSTYPES</filename> variable.
+        </para>
+
+        <note>
+            The entire image generation process is run under Pseudo.
+            Running under Pseudo ensures that the files in the root
+            filesystem have correct ownership.
+        </note>
+    </section>
+
+    <section id='sdk-generation-dev-environment'>
+        <title>SDK Generation</title>
+
+        <para>
+            The OpenEmbedded build system uses BitBake to generate the
+            Software Development Kit (SDK) installer script:
+            <imagedata fileref="figures/sdk-generation.png" align="center" width="6in" depth="7in" />
+        </para>
+
+        <para>
+            Like image generation, the SDK script process consists of
+            several stages and depends on many variables.
+            The <filename>do_populate_sdk</filename> task uses these
+            key variables to help create the list of packages to actually
+            install.
+        </para>
+
+        <para>
+            The <filename>do_populate_sdk</filename> task handles two
+            parts: a target part and a host part.
+            The target part is the part built for the target hardware and
+            includes libraries and headers.
+            The host part is the part of the SDK that runs on the
+            <filename>SDKMACHINE</filename>.
+        </para>
+
+        <para>
+            Once both parts are constructed, the
+            <filename>do_populate_sdk</filename> task performs some cleanup
+            on both parts.
+            After the cleanup, the task creates a cross-development
+            environment setup script and any configuration files that
+            might be needed.
+        </para>
+
+        <para>
+            The final output of the task is the Cross-development
+            toolchain installation script (<filename>.sh</filename> file),
+            which includes the environment setup script.
+        </para>
     </section>
 </chapter>