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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
<chapter id='usingpoky'>
<title>Using the Yocto Project</title>
<para>
This chapter describes common usage for the Yocto Project.
The information is introductory in nature as other manuals in the Yocto Project
documentation set provide more details on how to use the Yocto Project.
</para>
<section id='usingpoky-build'>
<title>Running a Build</title>
<para>
This section provides a summary of the build process and provides information
for less obvious aspects of the build process.
For general information on how to build an image using the OpenEmbedded build
system, see the
"<ulink url='&YOCTO_DOCS_QS_URL;#qs-building-images'>Building Images</ulink>"
section of the Yocto Project Quick Start.
</para>
<section id='build-overview'>
<title>Build Overview</title>
<para>
In the development environment you will need to build an image whenever you change hardware
support, add or change system libraries, or add or change services that have dependencies.
</para>
<mediaobject>
<imageobject>
<imagedata fileref="figures/building-an-image.png" format="PNG" align='center' scalefit='1'/>
</imageobject>
<caption>
<para>Building an Image</para>
</caption>
</mediaobject>
<para>
The first thing you need to do is set up the OpenEmbedded build
environment by sourcing an environment setup script
(i.e.
<link linkend='structure-core-script'><filename>&OE_INIT_FILE;</filename></link>
or
<link linkend='structure-memres-core-script'><filename>oe-init-build-env-memres</filename></link>).
Here is an example:
<literallayout class='monospaced'>
$ source &OE_INIT_FILE; [<replaceable>build_dir</replaceable>]
</literallayout>
</para>
<para>
The <replaceable>build_dir</replaceable> argument is optional and specifies the directory the
OpenEmbedded build system uses for the build -
the <ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
If you do not specify a Build Directory, it defaults to a directory
named <filename>build</filename> in your current working directory.
A common practice is to use a different Build Directory for different targets.
For example, <filename>~/build/x86</filename> for a <filename>qemux86</filename>
target, and <filename>~/build/arm</filename> for a <filename>qemuarm</filename> target.
</para>
<para>
Once the build environment is set up, you can build a target using:
<literallayout class='monospaced'>
$ bitbake <replaceable>target</replaceable>
</literallayout>
</para>
<para>
The <replaceable>target</replaceable> is the name of the recipe you want to build.
Common targets are the images in <filename>meta/recipes-core/images</filename>,
<filename>meta/recipes-sato/images</filename>, etc. all found in the
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
Or, the target can be the name of a recipe for a specific piece of software such as
BusyBox.
For more details about the images the OpenEmbedded build system supports, see the
"<link linkend="ref-images">Images</link>" chapter.
</para>
<note>
Building an image without GNU General Public License Version
3 (GPLv3), or similarly licensed, components is supported for
only minimal and base images.
See the "<link linkend='ref-images'>Images</link>" chapter for more information.
</note>
</section>
<section id='building-an-image-using-gpl-components'>
<title>Building an Image Using GPL Components</title>
<para>
When building an image using GPL components, you need to maintain your original
settings and not switch back and forth applying different versions of the GNU
General Public License.
If you rebuild using different versions of GPL, dependency errors might occur
due to some components not being rebuilt.
</para>
</section>
</section>
<section id='usingpoky-install'>
<title>Installing and Using the Result</title>
<para>
Once an image has been built, it often needs to be installed.
The images and kernels built by the OpenEmbedded build system are placed in the
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink> in
<filename class="directory">tmp/deploy/images</filename>.
For information on how to run pre-built images such as <filename>qemux86</filename>
and <filename>qemuarm</filename>, see the
"<ulink url='&YOCTO_DOCS_QS_URL;#using-pre-built'>Example Using Pre-Built Binaries and QEMU</ulink>"
section in the Yocto Project Application Developer's Guide.
For information about how to install these images, see the documentation for your
particular board or machine.
</para>
</section>
<section id='usingpoky-debugging'>
<title>Debugging Build Failures</title>
<para>
The exact method for debugging build failures depends on the nature of
the problem and on the system's area from which the bug originates.
Standard debugging practices such as comparison against the last
known working version with examination of the changes and the
re-application of steps to identify the one causing the problem are
valid for the Yocto Project just as they are for any other system.
Even though it is impossible to detail every possible potential failure,
this section provides some general tips to aid in debugging.
</para>
<para>
A useful feature for debugging is the error reporting tool.
Configuring the Yocto Project to use this tool causes the
OpenEmbedded build system to produce error reporting commands as
part of the console output.
You can enter the commands after the build completes
to log error information
into a common database, that can help you figure out what might be
going wrong.
For information on how to enable and use this feature, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-the-error-reporting-tool'>Using the Error Reporting Tool</ulink>"
section in the Yocto Project Development Manual.
</para>
<para>
For discussions on debugging, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#platdev-gdb-remotedebug'>Debugging With the GNU Project Debugger (GDB) Remotely</ulink>"
and
"<ulink url='&YOCTO_DOCS_DEV_URL;#adt-eclipse'>Working within Eclipse</ulink>"
sections in the Yocto Project Development Manual.
</para>
<note>
The remainder of this section presents many examples of the
<filename>bitbake</filename> command.
You can learn about BitBake by reading the
<ulink url='&YOCTO_DOCS_BB_URL;#bitbake-user-manual'>BitBake User Manual</ulink>.
</note>
<section id='usingpoky-debugging-taskfailures'>
<title>Task Failures</title>
<para>The log file for shell tasks is available in
<filename>${WORKDIR}/temp/log.do_<replaceable>taskname</replaceable>.pid</filename>.
For example, the <filename>do_compile</filename> task for the QEMU minimal image for the x86
machine (<filename>qemux86</filename>) might be
<filename>tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile.20830</filename>.
To see what
<ulink url='&YOCTO_DOCS_DEV_URL;#bitbake-term'>BitBake</ulink>
runs to generate that log, look at the corresponding
<filename>run.do_<replaceable>taskname</replaceable>.pid</filename> file located in the same directory.
</para>
<para>
Presently, the output from Python tasks is sent directly to the console.
</para>
</section>
<section id='usingpoky-debugging-taskrunning'>
<title>Running Specific Tasks</title>
<para>
Any given package consists of a set of tasks.
The standard BitBake behavior in most cases is:
<filename>do_fetch</filename>,
<filename>do_unpack</filename>,
<filename>do_patch</filename>, <filename>do_configure</filename>,
<filename>do_compile</filename>, <filename>do_install</filename>,
<filename>do_package</filename>,
<filename>do_package_write_*</filename>, and
<filename>do_build</filename>.
The default task is <filename>do_build</filename> and any tasks
on which it depends build first.
Some tasks, such as <filename>do_devshell</filename>, are not part
of the default build chain.
If you wish to run a task that is not part of the default build
chain, you can use the <filename>-c</filename> option in BitBake.
Here is an example:
<literallayout class='monospaced'>
$ bitbake matchbox-desktop -c devshell
</literallayout>
</para>
<para>
If you wish to rerun a task, use the <filename>-f</filename> force
option.
For example, the following sequence forces recompilation after
changing files in the work directory.
<literallayout class='monospaced'>
$ bitbake matchbox-desktop
.
.
<replaceable>make some changes to the source code in the work directory</replaceable>
.
.
$ bitbake matchbox-desktop -c compile -f
$ bitbake matchbox-desktop
</literallayout>
</para>
<para>
This sequence first builds and then recompiles
<filename>matchbox-desktop</filename>.
The last command reruns all tasks (basically the packaging tasks)
after the compile.
BitBake recognizes that the <filename>do_compile</filename>
task was rerun and therefore understands that the other tasks
also need to be run again.
</para>
<para>
You can view a list of tasks in a given package by running the
<filename>do_listtasks</filename> task as follows:
<literallayout class='monospaced'>
$ bitbake matchbox-desktop -c listtasks
</literallayout>
The results appear as output to the console and are also in the
file <filename>${WORKDIR}/temp/log.do_listtasks</filename>.
</para>
</section>
<section id='usingpoky-debugging-dependencies'>
<title>Dependency Graphs</title>
<para>
Sometimes it can be hard to see why BitBake wants to build
other packages before building a given package you have specified.
The <filename>bitbake -g <replaceable>targetname</replaceable></filename> command
creates the <filename>pn-buildlist</filename>,
<filename>pn-depends.dot</filename>,
<filename>package-depends.dot</filename>, and
<filename>task-depends.dot</filename> files in the current
directory.
These files show what will be built and the package and task
dependencies, which are useful for debugging problems.
You can use the
<filename>bitbake -g -u depexp <replaceable>targetname</replaceable></filename>
command to display the results in a more human-readable form.
</para>
</section>
<section id='usingpoky-debugging-bitbake'>
<title>General BitBake Problems</title>
<para>
You can see debug output from BitBake by using the <filename>-D</filename> option.
The debug output gives more information about what BitBake
is doing and the reason behind it.
Each <filename>-D</filename> option you use increases the logging level.
The most common usage is <filename>-DDD</filename>.
</para>
<para>
The output from <filename>bitbake -DDD -v</filename> <replaceable>targetname</replaceable> can reveal why
BitBake chose a certain version of a package or why BitBake
picked a certain provider.
This command could also help you in a situation where you think BitBake did something
unexpected.
</para>
</section>
<section id='development-host-system-issues'>
<title>Development Host System Issues</title>
<para>
Sometimes issues on the host development system can cause your
build to fail.
Following are known, host-specific problems.
Be sure to always consult the
<ulink url='&YOCTO_RELEASE_NOTES;'>Release Notes</ulink>
for a look at all release-related issues.
<itemizedlist>
<listitem><para><emphasis><filename>glibc-initial</filename> fails to build</emphasis>:
If your development host system has the unpatched
<filename>GNU Make 3.82</filename>,
the
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
task fails for <filename>glibc-initial</filename> during
the build.</para>
<para>Typically, every distribution that ships
<filename>GNU Make 3.82</filename> as
the default already has the patched version.
However, some distributions, such as Debian, have
<filename>GNU Make 3.82</filename> as an option, which
is unpatched.
You will see this error on these types of distributions.
Switch to <filename>GNU Make 3.81</filename> or patch
your <filename>make</filename> to solve the problem.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='usingpoky-debugging-buildfile'>
<title>Building with No Dependencies</title>
<para>
To build a specific recipe (<filename>.bb</filename> file),
you can use the following command form:
<literallayout class='monospaced'>
$ bitbake -b <replaceable>somepath</replaceable>/<replaceable>somerecipe</replaceable>.bb
</literallayout>
This command form does not check for dependencies.
Consequently, you should use it
only when you know existing dependencies have been met.
<note>
You can also specify fragments of the filename.
In this case, BitBake checks for a unique match.
</note>
</para>
</section>
<section id='usingpoky-debugging-variables'>
<title>Variables</title>
<para>
You can use the <filename>-e</filename> BitBake option to
display the parsing environment for a configuration.
The following displays the general parsing environment:
<literallayout class='monospaced'>
$ bitbake -e
</literallayout>
This next example shows the parsing environment for a specific
recipe:
<literallayout class='monospaced'>
$ bitbake -e <replaceable>recipename</replaceable>
</literallayout>
</para>
</section>
<section id='recipe-logging-mechanisms'>
<title>Recipe Logging Mechanisms</title>
<para>
Best practices exist while writing recipes that both log build progress and
act on build conditions such as warnings and errors.
Both Python and Bash language bindings exist for the logging mechanism:
<itemizedlist>
<listitem><para><emphasis>Python:</emphasis> For Python functions, BitBake
supports several loglevels: <filename>bb.fatal</filename>,
<filename>bb.error</filename>, <filename>bb.warn</filename>,
<filename>bb.note</filename>, <filename>bb.plain</filename>,
and <filename>bb.debug</filename>.</para></listitem>
<listitem><para><emphasis>Bash:</emphasis> For Bash functions, the same set
of loglevels exist and are accessed with a similar syntax:
<filename>bbfatal</filename>, <filename>bberror</filename>,
<filename>bbwarn</filename>, <filename>bbnote</filename>,
<filename>bbplain</filename>, and <filename>bbdebug</filename>.</para></listitem>
</itemizedlist>
</para>
<para>
For guidance on how logging is handled in both Python and Bash recipes, see the
<filename>logging.bbclass</filename> file in the
<filename>meta/classes</filename> folder of the
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
</para>
<section id='logging-with-python'>
<title>Logging With Python</title>
<para>
When creating recipes using Python and inserting code that handles build logs,
keep in mind the goal is to have informative logs while keeping the console as
"silent" as possible.
Also, if you want status messages in the log, use the "debug" loglevel.
</para>
<para>
Following is an example written in Python.
The code handles logging for a function that determines the
number of tasks needed to be run.
See the
"<link linkend='ref-tasks-listtasks'><filename>do_listtasks</filename></link>"
section for additional information:
<literallayout class='monospaced'>
python do_listtasks() {
bb.debug(2, "Starting to figure out the task list")
if noteworthy_condition:
bb.note("There are 47 tasks to run")
bb.debug(2, "Got to point xyz")
if warning_trigger:
bb.warn("Detected warning_trigger, this might be a problem later.")
if recoverable_error:
bb.error("Hit recoverable_error, you really need to fix this!")
if fatal_error:
bb.fatal("fatal_error detected, unable to print the task list")
bb.plain("The tasks present are abc")
bb.debug(2, "Finished figuring out the tasklist")
}
</literallayout>
</para>
</section>
<section id='logging-with-bash'>
<title>Logging With Bash</title>
<para>
When creating recipes using Bash and inserting code that handles build
logs, you have the same goals - informative with minimal console output.
The syntax you use for recipes written in Bash is similar to that of
recipes written in Python described in the previous section.
</para>
<para>
Following is an example written in Bash.
The code logs the progress of the <filename>do_my_function</filename> function.
<literallayout class='monospaced'>
do_my_function() {
bbdebug 2 "Running do_my_function"
if [ exceptional_condition ]; then
bbnote "Hit exceptional_condition"
fi
bbdebug 2 "Got to point xyz"
if [ warning_trigger ]; then
bbwarn "Detected warning_trigger, this might cause a problem later."
fi
if [ recoverable_error ]; then
bberror "Hit recoverable_error, correcting"
fi
if [ fatal_error ]; then
bbfatal "fatal_error detected"
fi
bbdebug 2 "Completed do_my_function"
}
</literallayout>
</para>
</section>
</section>
<section id='usingpoky-debugging-others'>
<title>Other Tips</title>
<para>
Here are some other tips that you might find useful:
<itemizedlist>
<listitem><para>When adding new packages, it is worth watching for
undesirable items making their way into compiler command lines.
For example, you do not want references to local system files like
<filename>/usr/lib/</filename> or <filename>/usr/include/</filename>.
</para></listitem>
<listitem><para>If you want to remove the <filename>psplash</filename>
boot splashscreen,
add <filename>psplash=false</filename> to the kernel command line.
Doing so prevents <filename>psplash</filename> from loading
and thus allows you to see the console.
It is also possible to switch out of the splashscreen by
switching the virtual console (e.g. Fn+Left or Fn+Right on a Zaurus).
</para></listitem>
</itemizedlist>
</para>
</section>
</section>
<section id='maintaining-build-output-quality'>
<title>Maintaining Build Output Quality</title>
<para>
Many factors can influence the quality of a build.
For example, if you upgrade a recipe to use a new version of an upstream software
package or you experiment with some new configuration options, subtle changes
can occur that you might not detect until later.
Consider the case where your recipe is using a newer version of an upstream package.
In this case, a new version of a piece of software might introduce an optional
dependency on another library, which is auto-detected.
If that library has already been built when the software is building,
the software will link to the built library and that library will be pulled
into your image along with the new software even if you did not want the
library.
</para>
<para>
The
<link linkend='ref-classes-buildhistory'><filename>buildhistory</filename></link>
class exists to help you maintain
the quality of your build output.
You can use the class to highlight unexpected and possibly unwanted
changes in the build output.
When you enable build history, it records information about the contents of
each package and image and then commits that information to a local Git
repository where you can examine the information.
</para>
<para>
The remainder of this section describes the following:
<itemizedlist>
<listitem><para>How you can enable and disable
build history</para></listitem>
<listitem><para>How to understand what the build history contains
</para></listitem>
<listitem><para>How to limit the information used for build history
</para></listitem>
<listitem><para>How to examine the build history from both a
command-line and web interface</para></listitem>
</itemizedlist>
</para>
<section id='enabling-and-disabling-build-history'>
<title>Enabling and Disabling Build History</title>
<para>
Build history is disabled by default.
To enable it, add the following <filename>INHERIT</filename>
statement and set the
<link linkend='var-BUILDHISTORY_COMMIT'><filename>BUILDHISTORY_COMMIT</filename></link>
variable to "1" at the end of your
<filename>conf/local.conf</filename> file found in the
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>:
<literallayout class='monospaced'>
INHERIT += "buildhistory"
BUILDHISTORY_COMMIT = "1"
</literallayout>
Enabling build history as previously described
causes the build process to collect build
output information and commit it to a local
<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink> repository.
<note>
Enabling build history increases your build times slightly,
particularly for images, and increases the amount of disk
space used during the build.
</note>
</para>
<para>
You can disable build history by removing the previous statements
from your <filename>conf/local.conf</filename> file.
</para>
</section>
<section id='understanding-what-the-build-history-contains'>
<title>Understanding What the Build History Contains</title>
<para>
Build history information is kept in
<filename>${</filename><link linkend='var-TOPDIR'><filename>TOPDIR</filename></link><filename>}/buildhistory</filename>
in the Build Directory as defined by the
<link linkend='var-BUILDHISTORY_DIR'><filename>BUILDHISTORY_DIR</filename></link>
variable.
The following is an example abbreviated listing:
<imagedata fileref="figures/buildhistory.png" align="center" width="6in" depth="4in" />
</para>
<para>
At the top level, there is a <filename>metadata-revs</filename> file
that lists the revisions of the repositories for the layers enabled
when the build was produced.
The rest of the data splits into separate
<filename>packages</filename>, <filename>images</filename> and
<filename>sdk</filename> directories, the contents of which are
described below.
</para>
<section id='build-history-package-information'>
<title>Build History Package Information</title>
<para>
The history for each package contains a text file that has
name-value pairs with information about the package.
For example, <filename>buildhistory/packages/i586-poky-linux/busybox/busybox/latest</filename>
contains the following:
<literallayout class='monospaced'>
PV = 1.22.1
PR = r32
RPROVIDES =
RDEPENDS = glibc (>= 2.20) update-alternatives-opkg
RRECOMMENDS = busybox-syslog busybox-udhcpc update-rc.d
PKGSIZE = 540168
FILES = /usr/bin/* /usr/sbin/* /usr/lib/busybox/* /usr/lib/lib*.so.* \
/etc /com /var /bin/* /sbin/* /lib/*.so.* /lib/udev/rules.d \
/usr/lib/udev/rules.d /usr/share/busybox /usr/lib/busybox/* \
/usr/share/pixmaps /usr/share/applications /usr/share/idl \
/usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers
FILELIST = /bin/busybox /bin/busybox.nosuid /bin/busybox.suid /bin/sh \
/etc/busybox.links.nosuid /etc/busybox.links.suid
</literallayout>
Most of these name-value pairs correspond to variables used
to produce the package.
The exceptions are <filename>FILELIST</filename>, which is the
actual list of files in the package, and
<filename>PKGSIZE</filename>, which is the total size of files
in the package in bytes.
</para>
<para>
There is also a file corresponding to the recipe from which the
package came (e.g.
<filename>buildhistory/packages/i586-poky-linux/busybox/latest</filename>):
<literallayout class='monospaced'>
PV = 1.22.1
PR = r32
DEPENDS = initscripts kern-tools-native update-rc.d-native \
virtual/i586-poky-linux-compilerlibs virtual/i586-poky-linux-gcc \
virtual/libc virtual/update-alternatives
PACKAGES = busybox-ptest busybox-httpd busybox-udhcpd busybox-udhcpc \
busybox-syslog busybox-mdev busybox-hwclock busybox-dbg \
busybox-staticdev busybox-dev busybox-doc busybox-locale busybox
</literallayout>
</para>
<para>
Finally, for those recipes fetched from a version control
system (e.g., Git), a file exists that lists source revisions
that are specified in the recipe and lists the actual revisions
used during the build.
Listed and actual revisions might differ when
<link linkend='var-SRCREV'><filename>SRCREV</filename></link>
is set to
<filename>${<link linkend='var-AUTOREV'>AUTOREV</link>}</filename>.
Here is an example assuming
<filename>buildhistory/packages/qemux86-poky-linux/linux-yocto/latest_srcrev</filename>):
<literallayout class='monospaced'>
# SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
# SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f"
SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f"
</literallayout>
You can use the <filename>buildhistory-collect-srcrevs</filename>
command with the <filename>-a</filename> option to
collect the stored <filename>SRCREV</filename> values
from build history and report them in a format suitable for
use in global configuration (e.g.,
<filename>local.conf</filename> or a distro include file) to
override floating <filename>AUTOREV</filename> values to a
fixed set of revisions.
Here is some example output from this command:
<literallayout class='monospaced'>
$ buildhistory-collect-srcrevs -a
# i586-poky-linux
SRCREV_pn-glibc = "b8079dd0d360648e4e8de48656c5c38972621072"
SRCREV_pn-glibc-initial = "b8079dd0d360648e4e8de48656c5c38972621072"
SRCREV_pn-opkg-utils = "53274f087565fd45d8452c5367997ba6a682a37a"
SRCREV_pn-kmod = "fd56638aed3fe147015bfa10ed4a5f7491303cb4"
# x86_64-linux
SRCREV_pn-gtk-doc-stub-native = "1dea266593edb766d6d898c79451ef193eb17cfa"
SRCREV_pn-dtc-native = "65cc4d2748a2c2e6f27f1cf39e07a5dbabd80ebf"
SRCREV_pn-update-rc.d-native = "eca680ddf28d024954895f59a241a622dd575c11"
SRCREV_glibc_pn-cross-localedef-native = "b8079dd0d360648e4e8de48656c5c38972621072"
SRCREV_localedef_pn-cross-localedef-native = "c833367348d39dad7ba018990bfdaffaec8e9ed3"
SRCREV_pn-prelink-native = "faa069deec99bf61418d0bab831c83d7c1b797ca"
SRCREV_pn-opkg-utils-native = "53274f087565fd45d8452c5367997ba6a682a37a"
SRCREV_pn-kern-tools-native = "23345b8846fe4bd167efdf1bd8a1224b2ba9a5ff"
SRCREV_pn-kmod-native = "fd56638aed3fe147015bfa10ed4a5f7491303cb4"
# qemux86-poky-linux
SRCREV_machine_pn-linux-yocto = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
SRCREV_meta_pn-linux-yocto = "a227f20eff056e511d504b2e490f3774ab260d6f"
# all-poky-linux
SRCREV_pn-update-rc.d = "eca680ddf28d024954895f59a241a622dd575c11"
</literallayout>
<note>
Here are some notes on using the
<filename>buildhistory-collect-srcrevs</filename> command:
<itemizedlist>
<listitem><para>By default, only values where the
<filename>SRCREV</filename> was
not hardcoded (usually when <filename>AUTOREV</filename>
was used) are reported.
Use the <filename>-a</filename> option to see all
<filename>SRCREV</filename> values.
</para></listitem>
<listitem><para>The output statements might not have any effect
if overrides are applied elsewhere in the build system
configuration.
Use the <filename>-f</filename> option to add the
<filename>forcevariable</filename> override to each output line
if you need to work around this restriction.
</para></listitem>
<listitem><para>The script does apply special handling when
building for multiple machines.
However, the script does place a
comment before each set of values that specifies
which triplet to which they belong as shown above
(e.g., <filename>i586-poky-linux</filename>).
</para></listitem>
</itemizedlist>
</note>
</para>
</section>
<section id='build-history-image-information'>
<title>Build History Image Information</title>
<para>
The files produced for each image are as follows:
<itemizedlist>
<listitem><para><filename>image-files:</filename>
A directory containing selected files from the root
filesystem.
The files are defined by
<link linkend='var-BUILDHISTORY_IMAGE_FILES'><filename>BUILDHISTORY_IMAGE_FILES</filename></link>.
</para></listitem>
<listitem><para><filename>build-id.txt:</filename>
Human-readable information about the build configuration
and metadata source revisions.
This file contains the full build header as printed
by BitBake.</para></listitem>
<listitem><para><filename>*.dot:</filename>
Dependency graphs for the image that are
compatible with <filename>graphviz</filename>.
</para></listitem>
<listitem><para><filename>files-in-image.txt:</filename>
A list of files in the image with permissions,
owner, group, size, and symlink information.
</para></listitem>
<listitem><para><filename>image-info.txt:</filename>
A text file containing name-value pairs with information
about the image.
See the following listing example for more information.
</para></listitem>
<listitem><para><filename>installed-package-names.txt:</filename>
A list of installed packages by name only.</para></listitem>
<listitem><para><filename>installed-package-sizes.txt:</filename>
A list of installed packages ordered by size.
</para></listitem>
<listitem><para><filename>installed-packages.txt:</filename>
A list of installed packages with full package
filenames.</para></listitem>
</itemizedlist>
<note>
Installed package information is able to be gathered and
produced even if package management is disabled for the final
image.
</note>
</para>
<para>
Here is an example of <filename>image-info.txt</filename>:
<literallayout class='monospaced'>
DISTRO = poky
DISTRO_VERSION = 1.7
USER_CLASSES = buildstats image-mklibs image-prelink
IMAGE_CLASSES = image_types
IMAGE_FEATURES = debug-tweaks
IMAGE_LINGUAS =
IMAGE_INSTALL = packagegroup-core-boot run-postinsts
BAD_RECOMMENDATIONS =
NO_RECOMMENDATIONS =
PACKAGE_EXCLUDE =
ROOTFS_POSTPROCESS_COMMAND = write_package_manifest; license_create_manifest; \
write_image_manifest ; buildhistory_list_installed_image ; \
buildhistory_get_image_installed ; ssh_allow_empty_password; \
postinst_enable_logging; rootfs_update_timestamp ; ssh_disable_dns_lookup ;
IMAGE_POSTPROCESS_COMMAND = buildhistory_get_imageinfo ;
IMAGESIZE = 6900
</literallayout>
Other than <filename>IMAGESIZE</filename>, which is the
total size of the files in the image in Kbytes, the
name-value pairs are variables that may have influenced the
content of the image.
This information is often useful when you are trying to determine
why a change in the package or file listings has occurred.
</para>
</section>
<section id='using-build-history-to-gather-image-information-only'>
<title>Using Build History to Gather Image Information Only</title>
<para>
As you can see, build history produces image information,
including dependency graphs, so you can see why something
was pulled into the image.
If you are just interested in this information and not
interested in collecting specific package or SDK information,
you can enable writing only image information without
any history by adding the following to your
<filename>conf/local.conf</filename> file found in the
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>:
<literallayout class='monospaced'>
INHERIT += "buildhistory"
BUILDHISTORY_COMMIT = "0"
BUILDHISTORY_FEATURES = "image"
</literallayout>
Here, you set the
<link linkend='var-BUILDHISTORY_FEATURES'><filename>BUILDHISTORY_FEATURES</filename></link>
variable to use the image feature only.
</para>
</section>
<section id='build-history-sdk-information'>
<title>Build History SDK Information</title>
<para>
Build history collects similar information on the contents
of SDKs (e.g. <filename>meta-toolchain</filename>
or <filename>bitbake -c populate_sdk imagename</filename>)
as compared to information it collects for images.
The following list shows the files produced for each SDK:
<itemizedlist>
<listitem><para><filename>files-in-sdk.txt:</filename>
A list of files in the SDK with permissions,
owner, group, size, and symlink information.
This list includes both the host and target parts
of the SDK.
</para></listitem>
<listitem><para><filename>sdk-info.txt:</filename>
A text file containing name-value pairs with information
about the SDK.
See the following listing example for more information.
</para></listitem>
<listitem><para>The following information appears under
each of the <filename>host</filename>
and <filename>target</filename> directories
for the portions of the SDK that run on the host and
on the target, respectively:
<itemizedlist>
<listitem><para><filename>depends.dot:</filename>
Dependency graph for the SDK that is
compatible with <filename>graphviz</filename>.
</para></listitem>
<listitem><para><filename>installed-package-names.txt:</filename>
A list of installed packages by name only.
</para></listitem>
<listitem><para><filename>installed-package-sizes.txt:</filename>
A list of installed packages ordered by size.
</para></listitem>
<listitem><para><filename>installed-packages.txt:</filename>
A list of installed packages with full package
filenames.</para></listitem>
</itemizedlist>
</para></listitem>
</itemizedlist>
</para>
<para>
Here is an example of <filename>sdk-info.txt</filename>:
<literallayout class='monospaced'>
DISTRO = poky
DISTRO_VERSION = 1.3+snapshot-20130327
SDK_NAME = poky-glibc-i686-arm
SDK_VERSION = 1.3+snapshot
SDKMACHINE =
SDKIMAGE_FEATURES = dev-pkgs dbg-pkgs
BAD_RECOMMENDATIONS =
SDKSIZE = 352712
</literallayout>
Other than <filename>SDKSIZE</filename>, which is the
total size of the files in the SDK in Kbytes, the
name-value pairs are variables that might have influenced the
content of the SDK.
This information is often useful when you are trying to
determine why a change in the package or file listings
has occurred.
</para>
</section>
<section id='examining-build-history-information'>
<title>Examining Build History Information</title>
<para>
You can examine build history output from the command line or
from a web interface.
</para>
<para>
To see any changes that have occurred (assuming you have
<link linkend='var-BUILDHISTORY_COMMIT'><filename>BUILDHISTORY_COMMIT = "1"</filename></link>),
you can simply
use any Git command that allows you to view the history of
a repository.
Here is one method:
<literallayout class='monospaced'>
$ git log -p
</literallayout>
You need to realize, however, that this method does show
changes that are not significant (e.g. a package's size
changing by a few bytes).
</para>
<para>
A command-line tool called <filename>buildhistory-diff</filename>
does exist, though, that queries the Git repository and prints just
the differences that might be significant in human-readable form.
Here is an example:
<literallayout class='monospaced'>
$ ~/poky/poky/scripts/buildhistory-diff . HEAD^
Changes to images/qemux86_64/glibc/core-image-minimal (files-in-image.txt):
/etc/anotherpkg.conf was added
/sbin/anotherpkg was added
* (installed-package-names.txt):
* anotherpkg was added
Changes to images/qemux86_64/glibc/core-image-minimal (installed-package-names.txt):
anotherpkg was added
packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras"
* PR changed from "r0" to "r1"
* PV changed from "0.1.10" to "0.1.12"
packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%)
* PR changed from "r0" to "r1"
* PV changed from "0.1.10" to "0.1.12"
</literallayout>
</para>
<para>
To see changes to the build history using a web interface, follow
the instruction in the <filename>README</filename> file here.
<ulink url='http://git.yoctoproject.org/cgit/cgit.cgi/buildhistory-web/'></ulink>.
</para>
<para>
Here is a sample screenshot of the interface:
<imagedata fileref="figures/buildhistory-web.png" align="center" scalefit="1" width="130%" contentdepth="130%" />
</para>
</section>
</section>
</section>
<section id='speeding-up-the-build'>
<title>Speeding Up the Build</title>
<para>
Build time can be an issue.
By default, the build system uses simple controls to try and maximize
build efficiency.
In general, the default settings for all the following variables
result in the most efficient build times when dealing with single
socket systems (i.e. a single CPU).
If you have multiple CPUs, you might try increasing the default
values to gain more speed.
See the descriptions in the glossary for each variable for more
information:
<itemizedlist>
<listitem><para>
<link linkend='var-BB_NUMBER_THREADS'><filename>BB_NUMBER_THREADS</filename>:</link>
The maximum number of threads BitBake simultaneously executes.
</para></listitem>
<listitem><para>
<ulink url='&YOCTO_DOCS_BB_URL;#var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename>:</ulink>
The number of threads BitBake uses during parsing.
</para></listitem>
<listitem><para>
<link linkend='var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename>:</link>
Extra options passed to the <filename>make</filename> command
during the
<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>
task in order to specify parallel compilation on the
local build host.
</para></listitem>
<listitem><para>
<link linkend='var-PARALLEL_MAKEINST'><filename>PARALLEL_MAKEINST</filename>:</link>
Extra options passed to the <filename>make</filename> command
during the
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
task in order to specify parallel installation on the
local build host.
</para></listitem>
</itemizedlist>
As mentioned, these variables all scale to the number of processor
cores available on the build system.
For single socket systems, this auto-scaling ensures that the build
system fundamentally takes advantage of potential parallel operations
during the build based on the build machine's capabilities.
</para>
<para>
Following are additional factors that can affect build speed:
<itemizedlist>
<listitem><para>
File system type:
The file system type that the build is being performed on can
also influence performance.
Using <filename>ext4</filename> is recommended as compared
to <filename>ext2</filename> and <filename>ext3</filename>
due to <filename>ext4</filename> improved features
such as extents.
</para></listitem>
<listitem><para>
Disabling the updating of access time using
<filename>noatime</filename>:
The <filename>noatime</filename> mount option prevents the
build system from updating file and directory access times.
</para></listitem>
<listitem><para>
Setting a longer commit:
Using the "commit=" mount option increases the interval
in seconds between disk cache writes.
Changing this interval from the five second default to
something longer increases the risk of data loss but decreases
the need to write to the disk, thus increasing the build
performance.
</para></listitem>
<listitem><para>
Choosing the packaging backend:
Of the available packaging backends, IPK is the fastest.
Additionally, selecting a singular packaging backend also
helps.
</para></listitem>
<listitem><para>
Using <filename>tmpfs</filename> for
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>
as a temporary file system:
While this can help speed up the build, the benefits are
limited due to the compiler using
<filename>-pipe</filename>.
The build system goes to some lengths to avoid
<filename>sync()</filename> calls into the
file system on the principle that if there was a significant
failure, the
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>
contents could easily be rebuilt.
</para></listitem>
<listitem><para>
Inheriting the
<link linkend='ref-classes-rm-work'><filename>rm_work</filename></link>
class:
Inheriting this class has shown to speed up builds due to
significantly lower amounts of data stored in the data
cache as well as on disk.
Inheriting this class also makes cleanup of
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>
faster, at the expense of being easily able to dive into the
source code.
File system maintainers have recommended that the fastest way
to clean up large numbers of files is to reformat partitions
rather than delete files due to the linear nature of partitions.
This, of course, assumes you structure the disk partitions and
file systems in a way that this is practical.
</para></listitem>
</itemizedlist>
Aside from the previous list, you should keep some trade offs in
mind that can help you speed up the build:
<itemizedlist>
<listitem><para>
Remove items from
<link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>
that you might not need.
</para></listitem>
<listitem><para>
Exclude debug symbols and other debug information:
If you do not need these symbols and other debug information,
disabling the <filename>*-dbg</filename> package generation
can speed up the build.
You can disable this generation by setting the
<link linkend='var-INHIBIT_PACKAGE_DEBUG_SPLIT'><filename>INHIBIT_PACKAGE_DEBUG_SPLIT</filename></link>
variable to "1".
</para></listitem>
<listitem><para>
Disable static library generation for recipes derived from
<filename>autoconf</filename> or <filename>libtool</filename>:
Following is an example showing how to disable static
libraries and still provide an override to handle exceptions:
<literallayout class='monospaced'>
STATICLIBCONF = "--disable-static"
STATICLIBCONF_sqlite3-native = ""
EXTRA_OECONF += "${STATICLIBCONF}"
</literallayout>
<note><title>Notes</title>
<itemizedlist>
<listitem><para>
Some recipes need static libraries in order to work
correctly (e.g. <filename>pseudo-native</filename>
needs <filename>sqlite3-native</filename>).
Overrides, as in the previous example, account for
these kinds of exceptions.
</para></listitem>
<listitem><para>
Some packages have packaging code that assumes the
presence of the static libraries.
If so, you might need to exclude them as well.
</para></listitem>
</itemizedlist>
</note>
</para></listitem>
</itemizedlist>
</para>
</section>
</chapter>
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