dev-manual: Applied review comments to building tiny section.
Fixes YOCTO #2568 These changes are based on Darren Hart's second review of this new section. (From yocto-docs rev: b61ef2b6cf96b45666e0f75753b76e0f875663b5) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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Scott Rifenbark
Richard Purdie
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184a6f0c88
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@ -2209,8 +2209,8 @@
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<para>
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This section presents information that shows you how you can
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trim your distribution to even smaller sizes than the
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8 Mbytes <filename>poky-tiny</filename> distribution that
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can be built out-of-the-box using the Yocto Project.
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<filename>poky-tiny</filename> distribution, which is around
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5 Mbytes, that can be built out-of-the-box using the Yocto Project.
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</para>
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<section id='tiny-system-overview'>
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@ -2269,19 +2269,21 @@
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<title>Understand What Gives Your Image Size</title>
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<para>
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You will need to have an image from which you can
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work.
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The Yocto Project ships with the ability to create a
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It is easiest to have something to start with when creating
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your own distribution.
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You can use the Yocto Project out-of-the-box to create the
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<filename>poky-tiny</filename> distribution.
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This distribution consists of a small, sub-8 Mbyte kernel
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that works with two shipped Board Support Packages (BSPs):
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Fish River Island 2 and QEMU.
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You can use this distribution as a starting point and trim
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the size down from there.
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If you need to build out the <filename>poky-tiny</filename>
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distribution, see the
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"<link linkend='creating-your-own-distribution'>Creating Your Own Distribution</link>"
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section for information.
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Ulitmately, you will want to make changes in your own
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distribution that are likely modeled after
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<filename>poky-tiny</filename>.
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<note>
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To use <filename>poky-tiny</filename> in your build,
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set the <filename>DISTRO</filename> variable in your
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<filename>local.conf</filename> file to "poky-tiny"
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as described in the
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"<link linkend='creating-your-own-distribution'>Creating Your Own Distribution</link>"
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section.
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</note>
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</para>
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<para>
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@ -2292,8 +2294,9 @@
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in the code), and BSS (uninitialized data) sections.
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Dynamic memory contains memory that is allocated at runtime,
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stacks, hash tables, and so forth.
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Temporary memory is decompressed from the expanded kernel
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after boot and also includes the <filename>__init__</filename>
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Temporary memory is recovered after the boot process.
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This memory consists of memory used for decompressing
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the kernel and for the <filename>__init__</filename>
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functions.
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</para>
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@ -2304,7 +2307,8 @@
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the <filename>scripts</filename> directory:
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<itemizedlist>
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<listitem><para><filename>ksize.py</filename>: Reports
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component sizes for the kernel files.</para></listitem>
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component sizes for the kernel build objects.
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</para></listitem>
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<listitem><para><filename>dirsize.py</filename>: Reports
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component sizes for the root filesystem.</para></listitem>
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</itemizedlist>
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@ -2503,6 +2507,55 @@
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</para>
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</section>
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<section id='look-for-other-ways-to-minimize-size'>
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<title>Look for Other Ways to Minimize Size</title>
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<para>
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Depending on your particular circumstances, other areas that you
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can trim likely exist.
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The key to finding these areas is through tools and methods
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described here combined with experimentation and iteration.
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Here are a couple of areas to experiment with:
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<itemizedlist>
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<listitem><para><filename>eglibc</filename>:
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In general, follow this process:
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<orderedlist>
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<listitem><para>Remove <filename>eglibc</filename>
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features from
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<ulink url='&YOCTO_DOCS_REF_URL;#var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></ulink>
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that you think you don't need.</para></listitem>
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<listitem><para>Build your distribution.
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</para></listitem>
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<listitem><para>If the build fails due to missing
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symbols in a package, determine if you can
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reconfigure the package to not need those
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features.
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For example, change the configuration to not
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support wide character support as is done for
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<filename>ncurses</filename>.
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Or, if support for those characters is needed,
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determine what <filename>eglibc</filename>
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features provide the support and restore the
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configuration.
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</para></listitem>
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<listitem><para>Rebuild and repeat the process.
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</para></listitem>
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</orderedlist></para></listitem>
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<listitem><para><filename>busybox</filename>:
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For BusyBox, use a process similar as described for
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<filename>eglibc</filename>.
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A difference is you will need to boot the resulting
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system to see if you are able to do everything you
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expect from the running system.
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You need to be sure to integrate configuration fragments
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into Busybox because BusyBox handles its own core
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features and then allows you to add configuration
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fragments on top.
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='iterate-on-the-process'>
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<title>Iterate on the Process</title>
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