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ref-manual: Rewrite of "Image Generation" and devtool text.
Rewrite of devtool reference section. This was a separate commit but got squashed wrong so it ended up with this commit. The changes to "Image Generation" section reflect the new, more detailed image generation figure (From yocto-docs rev: 827c6872b88c17d2d0c8d44b1024fff19076e505) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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Scott Rifenbark
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Richard Purdie
Richard Purdie
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@@ -993,11 +993,13 @@
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<para>
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The image generation process consists of several stages and
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depends on many variables.
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depends on several tasks and variables.
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The
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<link linkend='ref-tasks-rootfs'><filename>do_rootfs</filename></link>
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task uses these key variables
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to help create the list of packages to actually install:
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task creates the root filesystem (file and directory structure)
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for an image.
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This task uses several key variables to help create the list
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of packages to actually install:
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<itemizedlist>
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<listitem><para><link linkend='var-IMAGE_INSTALL'><filename>IMAGE_INSTALL</filename></link>:
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Lists out the base set of packages to install from
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@@ -1017,9 +1019,22 @@
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Determines the language(s) for which additional
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language support packages are installed.
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</para></listitem>
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<listitem><para><link linkend='var-PACKAGE_INSTALL'><filename>PACKAGE_INSTALL</filename></link>:
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The final list of packages passed to the package manager
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for installation into the image.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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With
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<link linkend='var-IMAGE_ROOTFS'><filename>IMAGE_ROOTFS</filename></link>
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pointing to the location of the filesystem under construction and
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the <filename>PACKAGE_INSTALL</filename> variable providing the
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final list of packages to install, the root file system is
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created.
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</para>
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<para>
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Package installation is under control of the package manager
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(e.g. smart/rpm, opkg, or apt/dpkg) regardless of whether or
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@@ -1027,13 +1042,11 @@
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At the end of the process, if package management is not
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enabled for the target, the package manager's data files
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are deleted from the root filesystem.
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</para>
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<para>
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During image generation, the build system attempts to run
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all post-installation scripts.
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Any that fail to run on the build host are run on the
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target when the target system is first booted.
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As part of the final stage of package installation, postinstall
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scripts that are part of the packages are run.
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Any scripts that fail to run
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on the build host are run on the target when the target system
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is first booted.
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If you are using a
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<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-read-only-root-filesystem'>read-only root filesystem</ulink>,
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all the post installation scripts must succeed during the
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@@ -1042,24 +1055,17 @@
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</para>
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<para>
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During Optimization, optimizing processes are run across
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the image.
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These processes include <filename>mklibs</filename> and
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<filename>prelink</filename>.
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The <filename>mklibs</filename> process optimizes the size
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of the libraries.
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A <filename>prelink</filename> process optimizes the dynamic
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linking of shared libraries to reduce start up time of
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executables.
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The final stages of the <filename>do_rootfs</filename> task
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handle post processing.
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Post processing includes creation of a manifest file and
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optimizations.
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</para>
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<para>
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Along with writing out the root filesystem image, the
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<filename>do_rootfs</filename> task creates a manifest file
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(<filename>.manifest</filename>) in the same directory as
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the root filesystem image that lists out, line-by-line, the
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installed packages.
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This manifest file is useful for the
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The manifest file (<filename>.manifest</filename>) resides
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in the same directory as the root filesystem image.
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This file lists out, line-by-line, the installed packages.
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The manifest file is useful for the
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<link linkend='ref-classes-testimage*'><filename>testimage</filename></link>
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class, for example, to determine whether or not to run
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specific tests.
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@@ -1069,21 +1075,54 @@
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</para>
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<para>
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Part of the image generation process includes compressing the
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root filesystem image.
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Compression is accomplished through several optimization
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routines designed to reduce the overall size of the image.
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Optimizing processes run across the image include
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<filename>mklibs</filename>, <filename>prelink</filename>,
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and any other post-processing commands as defined by the
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<link linkend='var-ROOTFS_POSTPROCESS_COMMAND'><filename>ROOTFS_POSTPROCESS_COMMAND</filename></link>
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variable.
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The <filename>mklibs</filename> process optimizes the size
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of the libraries, while the
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<filename>prelink</filename> process optimizes the dynamic
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linking of shared libraries to reduce start up time of
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executables.
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</para>
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<para>
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After the root filesystem has been constructed, the image
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generation process turns everything into an image file or
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a set of image files.
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After the root filesystem is built, processing begins on
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the image through the <filename>do_image</filename> task.
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The build system runs any pre-processing commands as defined
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by the
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<link linkend='var-IMAGE_PREPROCESS_COMMAND'><filename>IMAGE_PREPROCESS_COMMAND</filename></link>
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variable.
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This variable specifies a list of functions to call before
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the OpenEmbedded build system creates the final image output
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files.
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</para>
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<para>
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The <filename>do_image</filename> task dynamically creates
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other <filename>do_image_*</filename> tasks as needed, which
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include compressing the root filesystem image to reduce the
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overall size of the image.
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The process turns everything into an image file or a set of
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image files.
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The formats used for the root filesystem depend on the
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<link linkend='var-IMAGE_FSTYPES'><filename>IMAGE_FSTYPES</filename></link>
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variable.
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</para>
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<para>
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The final task involved in image creation is the
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<filename>do_image_complete</filename> task.
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This task completes the image by applying any image
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post processing as defined through the
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<link linkend='var-IMAGE_POSTPROCESS_COMMAND'><filename>IMAGE_POSTPROCESS_COMMAND</filename></link>
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variable.
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The variable specifies a list of functions to call once the
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OpenEmbedded build system has created the final image output
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files.
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</para>
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<note>
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The entire image generation process is run under Pseudo.
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Running under Pseudo ensures that the files in the root
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