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dev-manual: First draft of new init manager section. 

I created a first draft of a section titled "Selecting an
Initialization Manager."  The text was based on information
from Ross burton.  This is for the "systemd" support that
is new for 1.4.  There is a lot of work left on the section.
This is the first draft.

Reported-by: Ross Burton <ross.burton@intel.com>
(From yocto-docs rev: ad358b96834879abe8a10d89e77453e30799ac0a)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark 2013-03-27 18:23:25 -07:00 committed by Richard Purdie
parent 072b38a5c2
commit 4a4d342264
1 changed files with 91 additions and 36 deletions
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documentation/dev-manual/dev-manual-common-tasks.xml
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@ -1184,8 +1184,8 @@
<title>Working With Libraries</title> <title>Working With Libraries</title>
<para> <para>
Libraries are an integral part of your system. Libraries are an integral part of your system.
This section describes some common practices you might find This section describes some common practices you might find
helpful when working with libraries to build your system: helpful when working with libraries to build your system:
<itemizedlist> <itemizedlist>
<listitem><para><link linkend='including-static-library-files'>How to include static library files</link> <listitem><para><link linkend='including-static-library-files'>How to include static library files</link>
@ -1442,46 +1442,46 @@
<title>Installing Multiple Versions of the Same Library</title> <title>Installing Multiple Versions of the Same Library</title>
<para> <para>
Situations can exist where you need to install and use Situations can exist where you need to install and use
multiple versions of the same library on the same system multiple versions of the same library on the same system
at the same time. at the same time.
These situations almost always exist when a library API These situations almost always exist when a library API
changes and you have multiple pieces of software that changes and you have multiple pieces of software that
depend on the separate versions of the library. depend on the separate versions of the library.
To accomodate these situations, you can install multiple To accomodate these situations, you can install multiple
versions of the same library in parallel on the same system. versions of the same library in parallel on the same system.
</para> </para>
<para> <para>
The process is straight forward as long as the libraries use The process is straight forward as long as the libraries use
proper versioning. proper versioning.
With properly versioned libraries, all you need to do to With properly versioned libraries, all you need to do to
individually specify the libraries is create separate, individually specify the libraries is create separate,
appropriately named recipes where the appropriately named recipes where the
<ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink> part of the <ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink> part of the
name includes a portion that differentiates each library version name includes a portion that differentiates each library version
(e.g.the major part of the version number). (e.g.the major part of the version number).
Thus, instead of having a single recipe that loads one version Thus, instead of having a single recipe that loads one version
of a library (e.g. <filename>clutter</filename>), you provide of a library (e.g. <filename>clutter</filename>), you provide
multiple recipes that result in different versions multiple recipes that result in different versions
of the libraries you want. of the libraries you want.
As an example, the following two recipes would allow the As an example, the following two recipes would allow the
two separate versions of the <filename>clutter</filename> two separate versions of the <filename>clutter</filename>
library to co-exist on the same system: library to co-exist on the same system:
<literallayout class='monospaced'> <literallayout class='monospaced'>
clutter-1.6_1.6.20.bb clutter-1.6_1.6.20.bb
clutter-1.8_1.8.4.bb clutter-1.8_1.8.4.bb
</literallayout> </literallayout>
Additionally, if you have other recipes that depend on a given Additionally, if you have other recipes that depend on a given
library, you need to use the library, you need to use the
<ulink url='&YOCTO_DOCS_REF_URL;#var-DEPENDS'><filename>DEPENDS</filename></ulink> <ulink url='&YOCTO_DOCS_REF_URL;#var-DEPENDS'><filename>DEPENDS</filename></ulink>
variable to create the dependency. variable to create the dependency.
Continuing with the same example, if you want to have a recipe Continuing with the same example, if you want to have a recipe
depend on the 1.8 version of the <filename>clutter</filename> depend on the 1.8 version of the <filename>clutter</filename>
library, use the following in your recipe: library, use the following in your recipe:
<literallayout class='monospaced'> <literallayout class='monospaced'>
DEPENDS = "clutter-1.8" DEPENDS = "clutter-1.8"
</literallayout> </literallayout>
</para> </para>
</section> </section>
</section> </section>
@ -2197,9 +2197,9 @@
<para> <para>
Very small distributions have some significant advantages such Very small distributions have some significant advantages such
as requiring less on-die or in-package memory (cheaper), better as requiring less on-die or in-package memory (cheaper), better
performance through efficient cache usage, lower power requirements performance through efficient cache usage, lower power requirements
due to less memory, faster boot times, and reduced development due to less memory, faster boot times, and reduced development
overhead. overhead.
Some real-world examples where a very small distribution gives Some real-world examples where a very small distribution gives
you distinct advantages are digital cameras, medical devices, you distinct advantages are digital cameras, medical devices,
@ -2346,7 +2346,7 @@
<title>Trim the Root Filesystem</title> <title>Trim the Root Filesystem</title>
<para> <para>
The root filesystem is made up of packages for booting, The root filesystem is made up of packages for booting,
libraries, and applications. libraries, and applications.
To change things you can configure how the packaging happens, To change things you can configure how the packaging happens,
which changes the way you build them. which changes the way you build them.
@ -2366,7 +2366,7 @@
a certain size. a certain size.
This example filters out anything below 100 Kbytes. This example filters out anything below 100 Kbytes.
The sizes reported by the tool are uncompressed and thus, The sizes reported by the tool are uncompressed and thus,
will be smaller by a relatively constant factor in a will be smaller by a relatively constant factor in a
compressed root filesystem. compressed root filesystem.
When you examine your log file, you can focus on areas of the When you examine your log file, you can focus on areas of the
root filesystem that take up large amounts of memory. root filesystem that take up large amounts of memory.
@ -2390,7 +2390,7 @@
result in minimal impact on the feature set. result in minimal impact on the feature set.
For example, you might not need a VGA display. For example, you might not need a VGA display.
Or, you might be able to get by with <filename>devtmpfs</filename> Or, you might be able to get by with <filename>devtmpfs</filename>
and <filename>mdev</filename> instead of and <filename>mdev</filename> instead of
<filename>udev</filename>. <filename>udev</filename>.
</para> </para>
@ -2406,10 +2406,10 @@
<para> <para>
Finally, you should consider exactly the type of root Finally, you should consider exactly the type of root
filesystem you need to meet your needs while also reducing filesystem you need to meet your needs while also reducing
its size. its size.
For example, consider <filename>cramfs</filename>, For example, consider <filename>cramfs</filename>,
<filename>squashfs</filename>, <filename>ubifs</filename>, <filename>squashfs</filename>, <filename>ubifs</filename>,
<filename>ext2</filename>, or an <filename>initramfs</filename> <filename>ext2</filename>, or an <filename>initramfs</filename>
using <filename>initramfs</filename>. using <filename>initramfs</filename>.
Be aware that <filename>ext3</filename> requires a 1 Mbyte Be aware that <filename>ext3</filename> requires a 1 Mbyte
@ -2455,7 +2455,7 @@
drivers, networking, core kernel files, filesystem, sound, drivers, networking, core kernel files, filesystem, sound,
and so forth. and so forth.
The sizes reported by the tool are uncompressed and thus, The sizes reported by the tool are uncompressed and thus,
will be smaller by a relatively constant factor in a compressed will be smaller by a relatively constant factor in a compressed
kernel image. kernel image.
Look to reduce the areas that are large and taking up around Look to reduce the areas that are large and taking up around
the "90% rule". the "90% rule".
@ -3074,6 +3074,61 @@
</para> </para>
</section> </section>
<section id="selecting-an-initialization-manager">
<title>Selecting an Initialization Manager</title>
<para>
By default, the Yocto Project uses
<filename>SysVinit</filename> as the initialization manager.
However, support also exists for <filename>systemd</filename>.
If you want to use <filename>SysVinit</filename>, you do
not have to do anything.
But, if you want to use <filename>systemd</filename>, you must
take some steps as described in the following sections.
</para>
<section id='using-systemd-exclusively'>
<title>Using systemd Exclusively</title>
<para>
Set the following variables in your
<filename>local.conf</filename> file as follows:
<literallayout class='monospaced'>
DISTRO_FEATURES = "systemd"
VIRTUAL-RUNTIME_init-manager = "systemd"
</literallayout>
You can save some disk space by adding
<filename>sysvinit</filename> to the distribution features
considered for backfill as follows:
<literallayout class='monospaced'>
DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit"
</literallayout>
Doing so removes any redundant <filename>sysvinit</filename>
scripts.
</para>
</section>
<section id='use-systemd-for-the-main-image-and-use-sysvinit-for-the-rescue-image'>
<title>Use systemd for the Main Image and Use SysVinit for the Rescue Image</title>
<para>
Set the following variables in your
<filename>local.conf</filename> file as follows:
<literallayout class='monospaced'>
DISTRO_FEATURES = "systemd"
VIRTUAL-RUNTIME_init-manager = "systemd"
</literallayout>
Doing so causes your main image to use
<filename>packagegroup-core-boot</filename> and
<filename>systemd</filename>.
The rescue/minimal image cannot use this group.
However, it can install <filename>sysvinit</filename>
and the appropriate packages with have both
<filename>systemd</filename> and <filename>sysvinit</filename>.
</para>
</section>
</section>
<section id='excluding-recipes-from-the-build'> <section id='excluding-recipes-from-the-build'>
<title>Excluding Recipes From the Build</title> <title>Excluding Recipes From the Build</title>
@ -3269,10 +3324,10 @@
<para> <para>
Aside from the GDB cross-binary, you also need a GDB Aside from the GDB cross-binary, you also need a GDB
initialization file in the same top directory in which initialization file in the same top directory in which
your binary resides. your binary resides.
When you start GDB on your host development system, GDB When you start GDB on your host development system, GDB
finds this initialization file and executes all the finds this initialization file and executes all the
commands within. commands within.
For information on the <filename>.gdbinit</filename>, see For information on the <filename>.gdbinit</filename>, see
"<ulink url='http://sourceware.org/gdb/onlinedocs/gdb/'>Debugging with GDB</ulink>" "<ulink url='http://sourceware.org/gdb/onlinedocs/gdb/'>Debugging with GDB</ulink>"
@ -3289,7 +3344,7 @@
the following to set your root filesystem location the following to set your root filesystem location
by using a command with this form: by using a command with this form:
<literallayout class='monospaced'> <literallayout class='monospaced'>
set sysroot &lt;your-sysroot-path&gt; set sysroot &lt;your-sysroot-path&gt;
</literallayout> </literallayout>
</para> </para>
</section> </section>
@ -3298,17 +3353,17 @@
<title>Launch the Host GDB</title> <title>Launch the Host GDB</title>
<para> <para>
To launch the host GDB, you need to source the To launch the host GDB, you need to source the
cross-debugging environment script, which if you installed cross-debugging environment script, which if you installed
the root filesystem in the default location is at the root filesystem in the default location is at
<filename>/opt/poky/&DISTRO;</filename> and begins with the <filename>/opt/poky/&DISTRO;</filename> and begins with the
string "environment-setup". string "environment-setup".
</para> </para>
<para> <para>
Finally, run the <filename>cross-gdb</filename> binary Finally, run the <filename>cross-gdb</filename> binary
and provide the inferior binary as part of the command line. and provide the inferior binary as part of the command line.
For example, the following command form continues with the For example, the following command form continues with the
example used in the previous section. example used in the previous section.
This command form loads the <filename>foo</filename> binary This command form loads the <filename>foo</filename> binary
as well as the debugging information: as well as the debugging information: