Copyright © 2007 OpenedHand Limited
Permission is granted to copy, distribute and/or modify this document under the terms of the Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales as published by Creative Commons.
| Revision History | |
|---|---|
| Revision 3.1 | 15 Feburary 2008 |
| Poky 3.1 (Pinky) Documentation Release | |
Table of Contents
base.bbclassautotools.bbclassupdate-alternatives.bbclassupdate-rc.d.bbclassbinconfig.bbclassdebian.bbclasspkgconfig.bbclasssrc_distribute_local.bbclasscpan.bbclassdistutils.bbclassdevshell.bbclasspackage*.bbclasskernel.bbclassimage.bbclass and rootfs*.bbclasssanity.bbclassinsane.bbclasssiteinfo.bbclassTable of Contents
Poky is an open source platform build tool. It is a complete software development environment for the creation of Linux devices. It aids the design, development, building, debugging, simulation and testing of complete modern software stacks using Linux, the X Window System and GNOME Mobile based application frameworks. It is based on OpenEmbedded but has been customised with a particular focus.
Poky was setup to:
Provide an open source Linux, X11, Matchbox, GTK+, GNOME Mobile platform.
Create a focused, stable, subset of OpenEmbedded that can be easily and reliably built and developed upon.
Fully support a wide range of x86 and ARM hardware
OpenedHand is the principle developer and maintainer of Poky and uses it to:
Provide OpenedHand with stable R&D platform we can build and develop upon.
Demonstrate the skills available within OpenedHand and provide a showcase for our software products (such as the Matchbox and Pimlico software packages and Sato, the default user interface in Poky).
Provide a base we can supply to our clients for building and developing their customised platforms.
Poky is primarily a platform builder which generates filesystem images based on open source software such as the Kdrive X server, the Matchbox window manager, the GTK+ toolkit and the D-Bus message bus system. Images for many kinds of devices can be generated, however the standard example machines target QEMU system emulation (both x86 and ARM) and the ARM based Sharp Zaurus series of devices. Poky's ability to boot inside a QEMU emulator makes it particularly suitable as a test platform for development of embedded software.
An important component integrated within Poky is Sato, a GNOME Mobile based user interface environment. It is designed to work well with screens at very high DPI and restricted size, such as those often found on smartphones and PDAs. It is coded with focus on efficiency and speed so that it works smoothly on hand-held and other embedded hardware. It will sit neatly on top of any device using the GNOME Mobile stack, providing a well defined user experience.
The handbook is split into sections covering different aspects of Poky. The 'Using Poky' section gives an overview of the components that make up Poky followed by information about using and debugging the Poky build system. The 'Extending Poky' section gives information about how to extend and customise Poky along with advice on how to manage these changes. The 'Platform Development with Poky' section gives information about interaction between Poky and target hardware for common platform development tasks such as software development, debugging and profiling. The rest of the manual consists of several reference sections each giving details on a specific section of Poky functionality.
This manual applies to Poky Release 3.1 (Pinky).
We recommend Debian-based distributions, in particular a recent Ubuntu release (7.04 or newer), as the host system for Poky. Nothing in Poky is distribution specific and other distributions will most likely work as long as the appropriate prerequisites are installed - we know of Poky being used successfully on Redhat, SUSE, Gentoo and Slackware host systems.
On a Debian-based system, you need the following packages installed:
build-essential
python
diffstat
texinfo
texi2html
cvs
subversion
wget
gawk
help2man
bochsbios (only to run qemux86 images)
Debian users can add debian.o-hand.com to their APT sources (See http://debian.o-hand.com for instructions on doing this) and then run "apt-get install qemu poky-depends poky-scripts" which will automatically install all these dependencies. OpenedHand can also provide VMware images with Poky and all dependencies pre-installed if required.
Poky can use a system provided QEMU or build its own depending on how it's
configured. See the options in local.conf for more details.
If you want to try Poky, you can do so in a few commands. The example below checks out the Poky source code, sets up a build environment, builds an image and then runs that image under the QEMU emulator in ARM system emulation mode:
$ wget http://pokylinux.org/releases/pinky-3.1.tar.gz $ tar zxvf pinky-3.1.tar.gz $ cd pinky-3.1/ $ source poky-init-build-env $ bitbake poky-image-sato $ runqemu qemuarm
This process will need Internet access, about 3 GB of disk space available, and you should expect the build to take about 4 - 5 hours since it is building an entire Linux system from source including the toolchain!
To build for other machines see the MACHINE variable in build/conf/local.conf
which also contains other configuration information. The images/kernels built
by Poky are placed in the tmp/deploy/images
directory.
You could also run "poky-qemu zImage-qemuarm.bin poky-image-sato-qemuarm.ext2" within the images directory if you have the poky-scripts Debian package installed from debian.o-hand.com. This allows the QEMU images to be used standalone outside the Poky build environment.
To setup networking within QEMU see the QEMU/USB networking with IP masquerading section.
Prebuilt images from Poky are also available if you just want to run the system under QEMU. To use these you need to:
Add debian.o-hand.com to your APT sources (See http://debian.o-hand.com for instructions on doing this)
Install patched QEMU and poky-scripts:
$ apt-get install qemu poky-scripts
Download a Poky QEMU release kernel (*zImage*qemu*.bin) and compressed filesystem image (poky-image-*-qemu*.ext2.bz2) which you'll need to decompress with 'bzip2 -d'. These are available from the last release or from the autobuilder.
Start the image:
$ poky-qemu <kernel> <image>
A patched version of QEMU is required at present. A suitable version is available from http://debian.o-hand.com, it can be built by poky (bitbake qemu-native) or can be downloaded/built as part of the toolchain/SDK tarballs.
Periodically, we make releases of Poky and these are available at http://pokylinux.org/releases/. These are more stable and tested than the nightly development images.
We make nightly builds of Poky for testing purposes and to make the latest developments available. The output from these builds is available at http://pokylinux.org/autobuild/ where the numbers represent the svn revision the builds were made from.
Automated builds are available for "standard" Poky and for Poky SDKs and toolchains as well
as any testing versions we might have such as poky-bleeding. The toolchains can
be used either as external standalone toolchains or can be combined with Poky as a
prebuilt toolchain to reduce build time. Using the external toolchains is simply a
case of untarring the tarball into the root of your system (it only creates files in
/usr/local/poky) and then enabling the option
in local.conf.
Poky is available from our SVN repository located at http://svn.o-hand.com/repos/poky/trunk; a web interface to the repository can be accessed at http://svn.o-hand.com/view/poky/.
'trunk' is where the deveopment work takes place and you should use this if you're after to work with the latest cutting edge developments. It is possible trunk can suffer temporary periods of instability while new features are developed and if this is undesireable we recommend using one of the release branches.
Table of Contents
This section gives an overview of the components that make up Poky following by information about running poky builds and dealing with any problems that may arise.
At the core of Poky is the bitbake task executor together with various types of configuration files. This section gives an overview of bitbake and the configuration files, in particular what they are used for, and how they interact.
Bitbake handles the parsing and execution of the data files. The data itself is of various types; recipes which give details about particular pieces of software, class data which is an abstraction of common build information (e.g. how to build a Linux kernel) and configuration data for machines, policy decisions, etc., which acts as a glue and binds everything together. Bitbake knows how to combine multiple data sources together, each data source being referred to as a 'collection'.
The directory structure walkthrough section gives details on the meaning of specific directories but some brief details on the core components follows:
Bitbake is the tool at the heart of Poky and is responsible for parsing the metadata, generating a list of tasks from it and then executing them. To see a list of the options it supports look at bitbake --help.
The most common usage is bitbake packagename where
packagename is the name of the package you wish to build
(from now on called the target). This often equates to the first part of a .bb
filename, so to run the matchbox-desktop_1.2.3.bb file, you
might type bitbake matchbox-desktop.
Several different versions of matchbox-desktop might exist and
bitbake will choose the one selected by the distribution configuration
(more details about how bitbake chooses between different versions
and providers is available in the
'Preferences and Providers' section). Bitbake will also try to execute any
dependent tasks first so before building matchbox-desktop it
would build a cross compiler and glibc if not already built.
The .bb files are usually referred to as 'recipes'. In general, a recipe contains information about a single piece of software such as where to download the source, any patches that are needed, any special configuration options, how to compile the source files and how to package the compiled output.
'package' can also used to describe recipes but since the same word is used for the packaged output from Poky (i.e. .ipk or .deb files), this document will avoid it.
Class (.bbclass) files contain information which is useful to share between metadata files. An example is the autotools class which contains the common settings that any application using autotools would use. The classes reference section gives details on common classes and how to use them.
The configuration (.conf) files define various configuration variables which govern what Poky does. These are split into several areas, such as machine configuration options, distribution configuration options, compiler tuning options, general common configuration and user configuration (local.conf).
First the Poky build environment needs to be setup using the following command:
$ source poky-init-build-env
Once the Poky build environment is setup, a target can now be built using:
$ bitbake <target>
The target is the name of the recipe you want to build. Common targets are the
images (in meta/packages/images/)
or the name of a recipe for a specific piece of software like
busybox. More details about the standard images
are available in the image reference section.
Once an image has been built it often needs to be installed. The images/kernels built
by Poky are placed in the tmp/deploy/images
directory. Running qemux86 and qemuarm images is covered in the Running an Image section. See your
board/machine documentation for information about how to install these images.
Devices commonly have USB connectivity. To connect to the usbnet interface, on the host machine run:
modprobe usbnet ifconfig usb0 192.168.0.200 route add 192.168.0.202 usb0
On Ubuntu, Debian or similar distributions you can have the network automatically
configured. You can also enable masquerading between the QEMU system and the rest
of your network. To do this you need to edit /etc/network/interfaces to include:
allow-hotplug tap0
iface tap0 inet static
address 192.168.7.200
netmask 255.255.255.0
network 192.168.7.0
post-up iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.7.0/24
post-up echo 1 > /proc/sys/net/ipv4/ip_forward
post-up iptables -P FORWARD ACCEPT
This ensures the tap0 interface will be up everytime you run QEMU and it will have network/internet access.
Under emulation there are two steps to configure for internet access via tap0. The first step is to configure routing:
route add default gw 192.168.7.200 tap0
The second is to configure name resolution which is configured in the
/etc/resolv.conf file. The simplest solution is
to copy it's content from the host machine.
USB connections to devices can be setup and automated in a similar way.
First add the following to
/etc/network/interfaces:
allow-hotplug usb0
iface usb0 inet static
address 192.168.0.200
netmask 255.255.255.0
network 192.168.0.0
post-up iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.0.0/24
post-up echo 1 > /proc/sys/net/ipv4/ip_forward
post-up iptables -P FORWARD ACCEPT
and then to configure routing on the device you would use:
route add default gw 192.168.0.202 usb0
The exact method for debugging Poky depends on the nature of the bug(s) and which part of the system they might be from. Standard debugging practises such as comparing to the last known working version and examining the changes, reapplying the changes in steps to identify the one causing the problem etc. are valid for Poky just like any other system. Its impossible to detail every possible potential failure here but there are some general tips to aid debugging:
The log file for shell tasks is available in ${WORKDIR}/temp/log.do_taskname.pid.
For the compile task of busybox 1.01 on the ARM spitz machine, this
might be tmp/work/armv5te-poky-linux-gnueabi/busybox-1.01/temp/log.do_compile.1234
for example. To see what bitbake ran to generate that log, look at the run.do_taskname.pid
file in the same directory.
The output from python tasks is sent directly to the console at present.
Any given package consists of a set of tasks, in most cases the series is fetch, unpack, patch, configure, compile, install, package, package_write and build. The default task is "build" and any tasks this depends on are built first hence the standard bitbake behaviour. There are some tasks such as devshell which are not part of the default build chain. If you wish to run such a task you can use the "-c" option to bitbake e.g. bitbake matchbox-desktop -c devshell.
If you wish to rerun a task you can use the force option "-f". A typical usage session might look like:
% bitbake matchbox-desktop [change some source in the WORKDIR for example] % bitbake matchbox-desktop -c compile -f % bitbake matchbox-desktop
which would build matchbox-desktop, then recompile it. The final command reruns all tasks after the compile (basically the packaging tasks) since bitbake will notice the the compile has been rerun and hence the other tasks also need to run again.
You can view a list of tasks in a given package by running the listtasks task e.g. bitbake matchbox-desktop -c listtasks.
Sometimes it can be hard to see why bitbake wants to build
some other packages before a given package you've specified.
bitbake -g targetname will create
depends.dot and
task-depends.dot files in the current
directory. They show
which packages and tasks depend on which other packages and
tasks and are useful for debugging purposes.
Debug output from bitbake can be seen with the "-D" option. The debug output gives more information about what bitbake is doing and/or why. Each -D option increases the logging level, the most common usage being "-DDD".
The output from bitbake -DDD -v targetname can reveal why a certain version of a package might be chosen, why bitbake picked a certain provider or help in other situations where bitbake does something you're not expecting.
If you really want to build a specific .bb file, you can use the form bitbake -b somepath/somefile.bb. Note that this will not check the dependencies so this option should only be used when you know its dependencies already exist. You can specify fragments of the filename and bitbake will see if it can find a unique match.
The "-e" option will dump the resulting environment for either the configuration (no package specified) or for a specific package when specified with the "-b" option.
When adding new packages it is worth keeping an eye open for bad
things creeping into compiler commandlines such as references to local
system files (/usr/lib/ or /usr/include/ etc.).
If you want to remove the psplash boot splashscreen, add "psplash=false" to the kernel commandline and psplash won't load allowing you to see the console. It's also possible to switch out of the splashscreen by switching virtual console (Fn+Left or Fn+Right on a Zaurus).
Table of Contents
This section gives information about how to extend the functionality already present in Poky, documenting standard tasks such as adding new software packages, extending or customising images or porting poky to new hardware (adding a new machine). It also contains advice about how to manage the process of making changes to Poky to achieve best results.
To add package into Poky you need to write a recipe for it. Writing a recipe means creating a .bb file which sets various variables. The variables useful for recipes are detailed in the recipe reference section along with more detailed information about issues such as recipe naming.
The simplest way to add a new package is to base it on a similar pre-existing recipe. There are some examples below of how to add standard types of packages:
To build an application from a single file stored locally requires a
recipe which has the file listed in the SRC_URI variable. In addition
the do_compile and do_install
tasks need to be manually written. The
S variable defines the directory containing the source
code which in this case is set equal to
WORKDIR, the directory BitBake uses for the build.
DESCRIPTION = "Simple helloworld application"
SECTION = "examples"
LICENSE = "MIT"
SRC_URI = "file://helloworld.c"
S = "${WORKDIR}"
do_compile() {
${CC} helloworld.c -o helloworld
}
do_install() {
install -d ${D}${bindir}
install -m 0755 helloworld ${D}${bindir}
}
As a result of the build process "helloworld" and "helloworld-dbg" packages will be built.
Applications which use autotools (autoconf, automake)
require a recipe which has a source archive listed in
SRC_URI and
inherit autotools to instruct BitBake to use the
autotools.bbclass which has
definitions of all the steps
needed to build an autotooled application.
The result of the build will be automatically packaged and if
the application uses NLS to localise then packages with
locale information will be generated (one package per
language).
DESCRIPTION = "GNU Helloworld application"
SECTION = "examples"
LICENSE = "GPLv2"
SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.bz2"
inherit autotools
Applications which use GNU make require a recipe which has
the source archive listed in SRC_URI.
Adding a do_compile step
is not needed as by default BitBake will start the "make"
command to compile the application. If there is a need for
additional options to make then they should be stored in the
EXTRA_OEMAKE variable - BitBake
will pass them into the GNU
make invocation. A do_install task is required
- otherwise BitBake will run an empty do_install
task by default.
Some applications may require extra parameters to be passed to the compiler, for example an additional header path. This can be done buy adding to the CFLAGS variable, as in the example below.
DESCRIPTION = "Tools for managing memory technology devices."
SECTION = "base"
DEPENDS = "zlib"
HOMEPAGE = "http://www.linux-mtd.infradead.org/"
LICENSE = "GPLv2"
SRC_URI = "ftp://ftp.infradead.org/pub/mtd-utils/mtd-utils-${PV}.tar.gz"
CFLAGS_prepend = "-I ${S}/include "
do_install() {
oe_runmake install DESTDIR=${D}
}
The variables PACKAGES and FILES are used to split an application into multiple packages.
Below the "libXpm" recipe is used as an example. By default the "libXpm" recipe generates one package which contains the library and also a few binaries. The recipe can be adapted to split the binaries into separate packages.
require xorg-lib-common.inc
DESCRIPTION = "X11 Pixmap library"
LICENSE = "X-BSD"
DEPENDS += "libxext"
PE = "1"
XORG_PN = "libXpm"
PACKAGES =+ "sxpm cxpm"
FILES_cxpm = "${bindir}/cxpm"
FILES_sxpm = "${bindir}/sxpm"
In this example we want to ship the "sxpm" and "cxpm" binaries in separate packages. Since "bindir" would be packaged into the main PN package as standard we prepend the PACKAGES variable so additional package names are added to the start of list. The extra FILES_* variables then contain information to specify which files and directories goes into which package.
To add a post-installation script to a package, add
a pkg_postinst_PACKAGENAME()
function to the .bb file
where PACKAGENAME is the name of the package to attach
the postinst script to. A post-installation function has the following structure:
pkg_postinst_PACKAGENAME () {
#!/bin/sh -e
# Commands to carry out
}
The script defined in the post installation function gets called when the rootfs is made. If the script succeeds, the package is marked as installed. If the script fails, the package is marked as unpacked and the script will be executed again on the first boot of the image.
Sometimes it is necessary that the execution of a post-installation script is delayed until the first boot, because the script needs to be executed the device itself. To delay script execution until boot time, the post-installation function should have the following structure:
pkg_postinst_PACKAGENAME () {
#!/bin/sh -e
if [ x"$D" = "x" ]; then
# Actions to carry out on the device go here
else
exit 1
fi
}
The structure above delays execution until first boot because the D variable points to the 'image' directory when the rootfs is being made at build time but is unset when executed on the first boot.
Poky images can be customised to satisfy particular requirements. Several methods are detailed below along with guidelines of when to use them.
One way to get additional software into an image is by creating a custom image. The recipe will contain two lines:
IMAGE_INSTALL = "task-poky-x11-base package1 package2"
inherit poky-image
By creating a custom image, a developer has total control over the contents of the image. It is important use the correct names of packages in the IMAGE_INSTALL variable. The names must be in the OpenEmbedded notation instead of Debian notation, for example "glibc-dev" instead of "libc6-dev" etc.
The other method of creating a new image is by modifying an existing image. For example if a developer wants to add "strace" into "poky-image-sato" the following recipe can be used:
require poky-image-sato.bb
IMAGE_INSTALL += "strace"
For for complex custom images, the best approach is to create a custom
task package which is them used to build the image (or images). A good
example of a tasks package is meta/packages/tasks/task-poky.bb
. The PACKAGES
variable lists the task packages to build (along with the complimentary
-dbg and -dev packages). For each package added,
RDEPENDS and
RRECOMMENDS
entries can then be added each containing a list of packages the parent
task package should contain. An example would be:
DESCRIPTION = "My Custom Tasks"
PACKAGES = "\
task-custom-apps \
task-custom-apps-dbg \
task-custom-apps-dev \
task-custom-tools \
task-custom-tools-dbg \
task-custom-tools-dev \
"
RDEPENDS_task-custom-apps = "\
dropbear \
portmap \
psplash"
RDEPENDS_task-custom-tools = "\
oprofile \
oprofileui-server \
lttng-control \
lttng-viewer"
RRECOMMENDS_task-custom-tools = "\
kernel-module-oprofile"
In this example, two tasks packages are created, task-custom-apps and task-custom-tools with the dependencies and recommended package dependencies listed. To build an image using these task packages, you would then add "task-custom-apps" and/or "task-custom-tools" to IMAGE_INSTALL or other forms of image dependencies as described in other areas of this section.
Ultimately users may want to add extra image "features" as used by Poky with the
IMAGE_FEATURES
variable. To create these, the best reference is meta/classes/poky-image.bbclass
which illustrates how poky achieves this. In summary, the file looks at the contents of the
IMAGE_FEATURES
variable and based on this generates the
IMAGE_INSTALL variable automatically. Extra features can be added by
extending the class or creating a custom class for use with specialised image .bb files.
It is possible to customise image contents by abusing variables used by distribution maintainers in local.conf. This method only allows the addition of packages and is not recommended.
To add an "strace" package into the image the following is added to local.conf:
DISTRO_EXTRA_RDEPENDS += "strace"
However, since the DISTRO_EXTRA_RDEPENDS variable is for distribution maintainers this method does not make adding packages as simple as a custom .bb file. Using this method, a few packages will need to be recreated and the the image built.
bitbake -cclean task-boot task-base task-poky
bitbake poky-image-sato
Cleaning task-* packages is required because they use the DISTRO_EXTRA_RDEPENDS variable. There is no need to build them by hand as Poky images depend on the packages they contain so dependencies will be built automatically. For this reason we don't use the "rebuild" task in this case since "rebuild" does not care about dependencies - it only rebuilds the specified package.
Adding a new machine to Poky is a straightforward process and this section gives an idea of the changes that are needed. This guide is meant to cover adding machines similar to those Poky already supports. Adding a totally new architecture might require gcc/glibc changes as well as updates to the site information and, whilst well within Poky's capabilities, is outside the scope of this section.
A .conf file needs to be added to conf/machine/ with details of the device being added. The name of the file determines the name Poky will use to reference this machine.
The most important variables to set in this file are TARGET_ARCH (e.g. "arm"), PREFERRED_PROVIDER_virtual/kernel (see below) and MACHINE_FEATURES (e.g. "kernel26 apm screen wifi"). Other variables like SERIAL_CONSOLE (e.g. "115200 ttyS0"), KERNEL_IMAGETYPE (e.g. "zImage") and IMAGE_FSTYPES (e.g. "tar.gz jffs2") might also be needed. Full details on what these variables do and the meaning of their contents is available through the links.
Poky needs to be able to build a kernel for the machine. You need to either create a new kernel recipe for this machine or extend an existing recipe. There are plenty of kernel examples in the packages/linux directory which can be used as references.
If creating a new recipe the "normal" recipe writing rules apply for setting up a SRC_URI including any patches and setting S to point at the source code. You will need to create a configure task which configures the unpacked kernel with a defconfig be that through a "make defconfig" command or more usually though copying in a suitable defconfig and running "make oldconfig". By making use of "inherit kernel" and also maybe some of the linux-*.inc files, most other functionality is centralised and the the defaults of the class normally work well.
If extending an existing kernel it is usually a case of adding a suitable defconfig file in a location similar to that used by other machine's defconfig files in a given kernel, possibly listing it in the SRC_URI and adding the machine to the expression in COMPATIBLE_MACHINES .
A formfactor configuration file provides information about the target hardware on which Poky is running, and that Poky cannot obtain from other sources such as the kernel. Some examples of information contained in a formfactor configuration file include framebuffer orientation, whether or not the system has a keyboard, the positioning of the keyboard in relation to the screen, and screen resolution.
Sane defaults should be used in most cases, but if customisation is
necessary you need to create a machconfig file
under meta/packages/formfactor/files/MACHINENAME/
where MACHINENAME is the name for which this infomation
applies. For information about the settings available and the defaults, please see
meta/packages/formfactor/files/config.
We recognise that people will want to extend/configure/optimise Poky for their specific uses, especially due to the extreme configurability and flexibility Poky offers. To ensure ease of keeping pace with future changes in Poky we recommend making changes to Poky in a controlled way.
Poky supports the idea of "collections" which when used properly can massively ease future upgrades and allow segregation between the Poky core and a given developer's changes. Some other advice on managing changes to Poky is also given in the following section.
Often, people want to extend Poky either through adding packages or overriding files contained within Poky to add their own functionality. Bitbake has a powerful mechanism called collections which provide a way to handle this which is fully supported and actively encouraged within Poky.
In the standard tree, meta-extras is an example of how you can do this. As standard the data in meta-extras is not used on a Poky build but local.conf.sample shows how to enable it:
BBFILES := "${OEROOT}/meta/packages/*/*.bb ${OEROOT}/meta-extras/packages/*/*.bb"
BBFILE_COLLECTIONS = "normal extras"
BBFILE_PATTERN_normal = "^${OEROOT}/meta/"
BBFILE_PATTERN_extras = "^${OEROOT}/meta-extras/"
BBFILE_PRIORITY_normal = "5"
BBFILE_PRIORITY_extras = "5"
As can be seen, the extra recipes are added to BBFILES. The BBFILE_COLLECTIONS variable is then set to contain a list of collection names. The BBFILE_PATTERN variables are regular expressions used to match files from BBFILES into a particular collection in this case by using the base pathname. The BBFILE_PRIORITY variable then assigns the different priorities to the files in different collections. This is useful in situations where the same package might appear in both repositories and allows you to choose which collection should 'win'.
This works well for recipes. For bbclasses and configuration files, you can use the BBPATH environment variable. In this case, the first file with the matching name found in BBPATH is the one that is used, just like the PATH variable for binaries.
Modifications to Poky are often managed under some kind of source revision control system. The policy for committing to such systems is important as some simple policy can significantly improve usability. The tips below are based on the policy that OpenedHand uses for commits to Poky.
It helps to use a consistent style for commit messages when committing changes. We've found a style where the first line of a commit message summarises the change and starts with the name of any package affected work well. Not all changes are to specific packages so the prefix could also be a machine name or class name instead. If a change needs a longer description this should follow the summary.
Any commit should be self contained in that it should leave the metadata in a consistent state, buildable before and after the commit. This helps ensure the autobuilder test results are valid but is good practice regardless.
If a committed change will result in changing the package output then the value of the PR variable needs to be increased (commonly referred to as 'bumped') as part of that commit. Only integer values are used and PR = "r0" should not be added into new recipes as this is default value. When upgrading the version of a package (PV), the PR variable should be removed.
The aim is that the package version will only ever increase. If for some reason PV will change and but not increase, the PE (Package Epoch) can be increased (it defaults to '0'). The version numbers aim to follow the Debian Version Field Policy Guidelines which define how versions are compared and hence what "increasing" means.
There are two reasons for doing this, the first is to ensure that when a developer updates and rebuilds, they get all the changes to the repository and don't have to remember to rebuild any sections. The second is to ensure that target users are able to upgrade their devices via their package manager such as with the ipkg update;ipkg upgrade commands (or similar for dpkg/apt or rpm based systems). The aim is to ensure Poky has upgradable packages in all cases.
Poky is usually used to build software rather than modifying it. However, there are ways Poky can be used to modify software.
During building, the sources are available in WORKDIR directory.
Where exactly this is depends on the type of package and the
architecture of target device. For a standard recipe not
related to MACHINE it will be
tmp/work/PACKAGE_ARCH-poky-TARGET_OS/PN-PV-PR/.
Target device dependent packages use MACHINE
instead of PACKAGE_ARCH
in the directory name.
Check the package recipe sets the S variable to something
other than standard WORKDIR/PN-PV/ value.
After building a package, a user can modify the package source code without problem. The easiest way to test changes is by calling the "compile" task:
bitbake --cmd compile --force NAME_OF_PACKAGE
Other tasks may also be called this way.
By default Poky uses quilt
to manage patches in do_patch task.
It is a powerful tool which can be used to track all
modifications done to package sources.
Before modifying source code it is important to notify quilt so it will track changes into new patch file:
quilt new NAME-OF-PATCH.patch
Then add all files which will be modified into that patch:
quilt add file1 file2 file3
Now start editing. At the end quilt needs to be used to generate final patch which will contain all modifications:
quilt refresh
The resulting patch file can be found in the
patches/ subdirectory of the source
(S) directory. For future builds it
should be copied into
Poky metadata and added into SRC_URI of a recipe:
SRC_URI += "file://NAME-OF-PATCH.patch;patch=1"
This also requires a bump of PR value in the same recipe as we changed resulting packages.
Poky supports several methods of software development. These different forms of development are explained below and can be switched between as needed.
An Anjuta IDE plugin exists to make developing software within the Poky framework easier for the application developer. It presents a graphical IDE from which the developer can cross compile an application then deploy and execute the output in a QEMU emulation session. It also supports cross debugging and profiling.
To use the plugin, a toolchain and SDK built by Poky is required along with Anjuta and the Anjuta plugin. The Poky Anjuta plugin is available from the OpenedHand SVN repository located at http://svn.o-hand.com/repos/anjuta-poky/trunk/anjuta-plugin-sdk/; a web interface to the repository can be accessed at http://svn.o-hand.com/view/anjuta-poky/. See the README file contained in the project for more information.
The meta-toolchain and meta-toolchain-sdk targets (see
the images section) build tarballs which contain toolchains and
libraries suitable for application development outside Poky. These unpack into the
/usr/local/poky directory and contain
a setup script, e.g.
/usr/local/poky/eabi-glibc/arm/environment-setup which
can be sourced to initialise a suitable environment. After sourcing this, the
compiler, QEMU scripts, QEMU binary, a special version of pkgconfig and other
useful utilities are added to the PATH. Variables to assist pkgconfig and
autotools are also set so that, for example, configure can find pre-generated test
results for tests which need target hardware to run.
Using the toolchain with autotool enabled packages is straightforward, just pass the appropriate host option to configure e.g. "./configure --host=arm-poky-linux-gnueabi". For other projects it is usually a case of ensuring the cross tools are used e.g. CC=arm-poky-linux-gnueabi-gcc and LD=arm-poky-linux-gnueabi-ld.
Running Poky QEMU images is covered in the Running an Image section.
Poky's QEMU images contain a complete native toolchain. This means
that applications can be developed within QEMU in the same was as a
normal system. Using qemux86 on an x86 machine is fast since the
guest and host architectures match, qemuarm is slower but gives
faithful emulation of ARM specific issues. To speed things up these
images support using distcc to call a cross-compiler outside the
emulated system too. If runqemu was used to start
QEMU, and distccd is present on the host system, any bitbake cross
compiling toolchain available from the build system will automatically
be used from within qemu simply by calling distcc
(export CC="distcc" can be set in the enviroment).
Alterntatively, if a suitable SDK/toolchain is present in
/usr/local/poky it will also
automatically be used.
There are several options for connecting into the emulated system. QEMU provides a framebuffer interface which has standard consoles available. There is also a serial connection available which has a console to the system running on it and IP networking as standard. The images have a dropbear ssh server running with the root password disabled allowing standard ssh and scp commands to work. The images also contain an NFS server exporting the guest's root filesystem allowing that to be made available to the host.
If you have a system that matches the architecture of the Poky machine you're using, such as qemux86, you can run binaries directly from the image on the host system using a chroot combined with tools like Xephyr.
Poky has some scripts to make using its qemux86 images within a chroot easier. To use
these you need to install the poky-scripts package or otherwise obtain the
poky-chroot-setup and poky-chroot-run scripts.
You also need Xephyr and chrootuid binaries available. To initialize a system use the setup script:
# poky-chroot-setup <qemux86-rootfs.tgz> <target-directory>
which will unpack the specified qemux86 rootfs tarball into the target-directory. You can then start the system with:
# poky-chroot-run <target-directory> <command>
where the target-directory is the place the rootfs was unpacked to and command is an optional command to run. If no command is specified, the system will drop you within a bash shell. A Xephyr window will be displayed containing the emulated system and you may be asked for a password since some of the commands used for bind mounting directories need to be run using sudo.
There are limits as to how far the the realism of the chroot environment extends. It is useful for simple development work or quick tests but full system emulation with QEMU offers a much more realistic environment for more complex development tasks. Note that chroot support within Poky is still experimental.
Working directly in Poky is a fast and effective development technique. The idea is that you can directly edit files in WORKDIR or the source directory S and then force specific tasks to rerun in order to test the changes. An example session working on the matchbox-desktop package might look like this:
$ bitbake matchbox-desktop $ sh $ cd tmp/work/armv5te-poky-linux-gnueabi/matchbox-desktop-2.0+svnr1708-r0/ $ cd matchbox-desktop-2 $ vi src/main.c $ exit $ bitbake matchbox-desktop -c compile -f $ bitbake matchbox-desktop
Here, we build the package, change into the work directory for the package, change a file, then recompile the package. Instead of using sh like this, you can also use two different terminals. The risk with working like this is that a command like unpack could wipe out the changes you've made to the work directory so you need to work carefully.
It is useful when making changes directly to the work directory files to do so using quilt as detailed in the modifying packages with quilt section. The resulting patches can be copied into the recipe directory and used directly in the SRC_URI.
For a review of the skills used in this section see Sections 2.1.1 and 2.4.2.
When debugging certain commands or even to just edit packages, the 'devshell' can be a useful tool. To start it you run a command like:
$ bitbake matchbox-desktop -c devshell
which will open a terminal with a shell prompt within the Poky environment. This means PATH is setup to include the cross toolchain, the pkgconfig variables are setup to find the right .pc files, configure will be able to find the Poky site files etc. Within this environment, you can run configure or compile command as if they were being run by Poky itself. You are also changed into the source (S) directory automatically. When finished with the shell just exit it or close the terminal window.
The default shell used by devshell is the gnome-terminal. Other
forms of terminal can also be used by setting the
TERMCMD and
TERMCMDRUN variables
in local.conf. For examples of the other options available, see
meta/conf/bitbake.conf. An external shell is
launched rather than opening directly into the original terminal
window to make interaction with bitbakes multiple threads easier
and also allow a client/server split of bitbake in the future
(devshell will still work over X11 forwarding or similar).
It is worth remembering that inside devshell you need to use the full compiler name such as arm-poky-linux-gnueabi-gcc instead of just gcc and the same applies to other applications from gcc, bintuils, libtool etc. Poky will have setup environmental variables such as CC to assist applications, such as make, find the correct tools.
If you're working on a recipe which pulls from an external SCM it is possible to have Poky notice new changes added to the SCM and then build the latest version. This only works for SCMs where its possible to get a sensible revision number for changes. Currently it works for svn, git and bzr repositories.
To enable this behaviour it is simply a case of adding SRCREV_pn- PN = "${AUTOREV}" to local.conf where PN is the name of the package for which you want to enable automatic source revision updating.
GDB (The GNU Project Debugger) allows you to examine running programs to understand and fix problems and also to perform postmortem style analsys of program crashes. It is available as a package within poky and installed by default in sdk images. It works best when -dbg packages for the application being debugged are installed as the extra symbols give more meaningful output from GDB.
Sometimes, due to memory or disk space constraints, it is not possible to use GDB directly on the remote target to debug applications. This is due to the fact that GDB needs to load the debugging information and the binaries of the process being debugged. GDB then needs to perform many computations to locate information such as function names, variable names and values, stack traces, etc. even before starting the debugging process. This places load on the target system and can alter the characteristics of the program being debugged.
This is where GDBSERVER comes into play as it runs on the remote target and does not load any debugging information from the debugged process. Instead, the debugging information processing is done by a GDB instance running on a distant computer - the host GDB. The host GDB then sends control commands to GDBSERVER to make it stop or start the debugged program, as well as read or write some memory regions of that debugged program. All the debugging information loading and processing as well as the heavy debugging duty is done by the host GDB, giving the GDBSERVER running on the target a chance to remain small and fast.
As the host GDB is responsible for loading the debugging information and doing the necessary processing to make actual debugging happen, the user has to make sure it can access the unstripped binaries complete with their debugging information and compiled with no optimisations. The host GDB must also have local access to all the libraries used by the debugged program. On the remote target the binaries can remain stripped as GDBSERVER does not need any debugging information there. However they must also be compiled without optimisation matching the host's binaries.
The binary being debugged on the remote target machine is hence referred to as the 'inferior' in keeping with GDB documentation and terminology. Further documentation on GDB, is available on on their site.
First, make sure gdbserver is installed on the target. If not, install the gdbserver package (which needs the libthread-db1 package).
To launch GDBSERVER on the target and make it ready to "debug" a program located at /path/to/inferior, connect to the target and launch:
$ gdbserver localhost:2345 /path/to/inferior
After that, gdbserver should be listening on port 2345 for debugging commands coming from a remote GDB process running on the host computer. Communication between the GDBSERVER and the host GDB will be done using TCP. To use other communication protocols please refer to the GDBSERVER documentation.
Running GDB on the host computer takes a number of stages, described in the following sections.
A suitable gdb cross binary is required which runs on your host computer but
knows about the the ABI of the remote target. This can be obtained from
the the Poky toolchain, e.g.
/usr/local/poky/eabi-glibc/arm/bin/arm-poky-linux-gnueabi-gdb
which "arm" is the target architecture and "linux-gnueabi" the target ABI.
Alternatively this can be built directly by Poky. To do this you would build the gdb-cross package so for example you would run:
bitbake gdb-cross
Once built, the cross gdb binary can be found at
tmp/cross/bin/<target-abi>-gdb
The inferior binary needs to be available to GDB complete with all debugging symbols in order to get the best possible results along with any libraries the inferior depends on and their debugging symbols. There are a number of ways this can be done.
Perhaps the easiest is to have an 'sdk' image corresponding to the plain image installed on the device. In the case of 'pky-image-sato', 'poky-image-sdk' would contain suitable symbols. The sdk images already have the debugging symbols installed so its just a question expanding the archive to some location and telling GDB where this is.
Alternatively, poky can build a custom directory of files for a specific debugging purpose by reusing its tmp/rootfs directory, on the host computer in a slightly different way to normal. This directory contains the contents of the last built image. This process assumes the image running on the target was the last image to be built by Poky, the package foo contains the inferior binary to be debugged has been built without without optimisation and has debugging information available.
Firstly you want to install the foo package to tmp/rootfs by doing:
tmp/staging/i686-linux/usr/bin/ipkg-cl -f \ tmp/work/<target-abi>/poky-image-sato-1.0-r0/temp/ipkg.conf -o \ tmp/rootfs/ update
then,
tmp/staging/i686-linux/usr/bin/ipkg-cl -f \ tmp/work/<target-abi>/poky-image-sato-1.0-r0/temp/ipkg.conf \ -o tmp/rootfs install foo tmp/staging/i686-linux/usr/bin/ipkg-cl -f \ tmp/work/<target-abi>/poky-image-sato-1.0-r0/temp/ipkg.conf \ -o tmp/rootfs install foo-dbg
which installs the debugging information too.
To launch the host GDB, run the cross gdb binary identified above with the inferior binary specified on the commandline:
<target-abi>-gdb rootfs/usr/bin/foo
This loads the binary of program foo as well as its debugging information. Once the gdb prompt appears, you must instruct GDB to load all the libraries of the inferior from tmp/rootfs:
set solib-absolute-prefix /path/to/tmp/rootfs
where /path/to/tmp/rootfs must be
the absolute path to tmp/rootfs or wherever the
binaries with debugging information are located.
Now, tell GDB to connect to the GDBSERVER running on the remote target:
target remote remote-target-ip-address:2345
Where remote-target-ip-address is the IP address of the remote target where the GDBSERVER is running. 2345 is the port on which the GDBSERVER is running.
Debugging can now proceed as normal, as if the debugging were being done on the local machine, for example to tell GDB to break in the main function, for instance:
break main
and then to tell GDB to "continue" the inferior execution,
continue
For more information about using GDB please see the project's online documentation at http://sourceware.org/gdb/download/onlinedocs/.
OProfile is a statistical profiler well suited to finding performance bottlenecks in both userspace software and the kernel. It provides answers to questions like "Which functions does my application spend the most time in when doing X?". Poky is well integrated with OProfile to make profiling applications on target hardware straightforward.
To use OProfile you need an image with OProfile installed. The easiest way to do this is with "tools-profile" in IMAGE_FEATURES. You also need debugging symbols to be available on the system where the analysis will take place. This can be achieved with "dbg-pkgs" in IMAGE_FEATURES or by installing the appropriate -dbg packages. For successful call graph analysis the binaries must preserve the frame pointer register and hence should be compiled with the "-fno-omit-framepointer" flag. In Poky this can be achieved with SELECTED_OPTIMIZATION = "-fexpensive-optimizations -fno-omit-framepointer -frename-registers -O2" or by setting DEBUG_BUILD = "1" in local.conf (the latter will also add extra debug information making the debug packages large).
All the profiling work can be performed on the target device. A simple OProfile session might look like:
# opcontrol --reset # opcontrol --start --separate=lib --no-vmlinux -c 5 [do whatever is being profiled] # opcontrol --stop $ opreport -cl
Here, the reset command clears any previously profiled data,
OProfile is then started. The options used to start OProfile mean
dynamic library data is kept separately per application, kernel
profiling is disabled and callgraphing is enabled up to 5 levels
deep. To profile the kernel, you would specify the
--vmlinux=/path/to/vmlinux option (the vmlinux file is usually in
/boot/ in Poky and must match the running kernel). The profile is
then stopped and the results viewed with opreport with options
to see the separate library symbols and callgraph information.
Callgraphing means OProfile not only logs infomation about which functions time is being spent in but also which functions called those functions (their parents) and which functions that function calls (its children). The higher the callgraphing depth, the more accurate the results but this also increased the loging overhead so it should be used with caution. On ARM, binaries need to have the frame pointer enabled for callgraphing to work (compile with the gcc option -fno-omit-framepointer).
For more information on using OProfile please see the OProfile online documentation at http://oprofile.sourceforge.net/docs/.
A graphical user interface for OProfile is also available. You can either use prebuilt Debian packages from the OpenedHand repository or download and build from svn at http://svn.o-hand.com/repos/oprofileui/trunk/. If the "tools-profile" image feature is selected, all necessary binaries are installed onto the target device for OProfileUI interaction.
In order to convert the data in the sample format from the target
to the host the opimport program is needed.
This is not included in standard Debian OProfile packages but an
OProfile package with this addition is also available from the OpenedHand repository.
We recommend using OProfile 0.9.3 or greater. Other patches to
OProfile may be needed for recent OProfileUI features, but Poky
usually includes all needed patches on the target device. Please
see the
OProfileUI README for up to date information, and the
OProfileUI website
for more information on the OProfileUI project.
This assumes a working network connection with the target
hardware. In this case you just need to run
"oprofile-server" on the device. By default it listens
on port 4224. This can be changed with the --port command line
option.
The client program is called oprofile-viewer. The UI is relatively straightforward, the key functionality is accessed through the buttons on the toolbar (which are duplicated in the menus.) These buttons are:
Connect - connect to the remote host, the IP address or hostname for the target can be supplied here.
Disconnect - disconnect from the target.
Start - start the profiling on the device.
Stop - stop the profiling on the device and download the data to the local host. This will generate the profile and show it in the viewer.
Download - download the data from the target, generate the profile and show it in the viewer.
Reset - reset the sample data on the device. This will remove the sample information that was collected on a previous sampling run. Ensure you do this if you do not want to include old sample information.
Save - save the data downloaded from the target to another directory for later examination.
Open - load data that was previously saved.
The behaviour of the client is to download the complete 'profile archive' from the target to the host for processing. This archive is a directory containing the sample data, the object files and the debug information for said object files. This archive is then converted using a script included in this distribution ('oparchconv') that uses 'opimport' to convert the archive from the target to something that can be processed on the host.
Downloaded archives are kept in /tmp and cleared up when they are no longer in use.
If you wish to profile into the kernel, this is possible, you just need to ensure a vmlinux file matching the running kernel is available. In Poky this is usually located in /boot/vmlinux-KERNELVERSION, where KERNEL-version is the version of the kernel e.g. 2.6.23. Poky generates separate vmlinux packages for each kernel it builds so it should be a question of just ensuring a matching package is installed ( ipkg install kernel-vmlinux. These are automatically installed into development and profiling images alongside OProfile. There is a configuration option within the OProfileUI settings page where the location of the vmlinux file can be entered.
Waiting for debug symbols to transfer from the device can be slow and it's not always necessary to actually have them on device for OProfile use. All that is needed is a copy of the filesystem with the debug symbols present on the viewer system. The GDB remote debug section covers how to create such a directory with Poky and the location of this directory can again be specified in the OProfileUI settings dialog. If specified, it will be used where the file checksums match those on the system being profiled.
If no network access to the target is available an archive for processing in 'oprofile-viewer' can be generated with the following set of command.
# opcontrol --reset # opcontrol --start --separate=lib --no-vmlinux -c 5 [do whatever is being profiled] # opcontrol --stop # oparchive -o my_archive
Where my_archive is the name of the archive directory where you would like the profile archive to be kept. The directory will be created for you. This can then be copied to another host and loaded using 'oprofile-viewer''s open functionality. The archive will be converted if necessary.
Poky consists of several components and understanding what these are and where they're located is one of the keys to using it. This section walks through the Poky directory structure giving information about the various files and directories.
A copy of BitBake is included within Poky for ease of use, and should
usually match the current BitBake stable release from the BitBake project.
Bitbake, a metadata interpreter, reads the Poky metadata and runs the tasks
defined in the Poky metadata. Failures are usually from the metadata, not
BitBake itself, so most users don't need to worry about BitBake. The
bitbake/bin/ directory is placed
into the PATH environment variable by the poky-init-build-env script.
For more information on BitBake please see the BitBake project site at http://bitbake.berlios.de/ and the BitBake on-line manual at http://bitbake.berlios.de/manual/.
This directory contains the core metadata, a key part of Poky. Within this directory there are definitions of the machines, the Poky distribution and the packages that make up a given system.
This directory is similar to meta/,
and contains some extra metadata not included in standard Poky. These are
disabled by default, and are not supported as part of Poky.
This directory contains various integration scripts which implement extra functionality in the Poky environment, such as the QEMU scripts. This directory is appended to the PATH environment variable by the poky-init-build-env script.
While not part of a checkout, Poky will create this directory as
part of any build. Any downloads are placed in this directory (as
specified by the DL_DIR
variable). This directory can be shared between Poky
builds to save downloading files multiple times. SCM checkouts are
also stored here as e.g. sources/svn/
, sources/cvs/ or
sources/git/ and the
sources directory may contain archives of checkouts for various
revisions or dates.
It's worth noting that BitBake creates .md5
stamp files for downloads. It uses these to mark downloads as
complete as well as for checksum and access accounting purposes. If you add
a file manually to the directory, you need to touch the corresponding
.md5 file too.
This location can be overridden by setting DL_DIR in local.conf
. This directory can be shared between builds and even between
machines via NFS, so downloads are only made once, speeding up builds.
This script is used to setup the Poky build environment. Sourcing this file in
a shell makes changes to PATH and sets other core BitBake variables based on the
current working directory. You need to use this before running Poky commands.
Internally it uses scripts within the scripts/
directory to do the bulk of the work.
This file contains all the local user configuration of Poky. If there
is no local.conf present, it is created from
local.conf.sample. The local.conf
file contains documentation on the various configuration options. Any
variable set here overrides any variable set elsewhere within Poky unless
that variable is hardcoded within Poky (e.g. by using '=' instead of '?=').
Some variables are hardcoded for various reasons but these variables are
relatively rare.
Edit this file to set the MACHINE for which you want to build, which package types you wish to use (PACKAGE_CLASSES) or where downloaded files should go (DL_DIR).
This is created by BitBake if it doesn't exist and is where all the Poky output
is placed. To clean Poky and start a build from scratch (other than downloads),
you can wipe this directory. The tmp/
directory has some important sub-components detailed below.
When BitBake parses the metadata it creates a cache file of the result which can be used when subsequently running commands. These are stored here on a per machine basis.
The cross compiler when generated is placed into this directory and those beneath it.
Any .deb packages emitted by Poky are placed here, sorted into feeds for different architecture types.
Complete filesystem images are placed here. If you want to flash the resulting image from a build onto a device, look here for them.
This is a temporary scratch area used when creating filesystem images. It is run under fakeroot and is not useful once that fakeroot session has ended as information is lost. It is left around since it is still useful in debugging image creation problems.
Any package needing to share output with other packages does so within staging. This means it contains any shared header files and any shared libraries amongst other data. It is subdivided by architecture so multiple builds can run within the one build directory.
This is used by BitBake for accounting purposes to keep track of which tasks have been run and when. It is also subdivided by architecture. The files are empty and the important information is the filenames and timestamps.
This directory contains various subdirectories for each architecture, and each package built by BitBake has its own work directory under the appropriate architecture subdirectory. All tasks are executed from this work directory. As an example, the source for a particular package will be unpacked, patched, configured and compiled all within its own work directory.
It is worth considering the structure of a typical work directory. An
example is the linux-rp kernel, version 2.6.20 r7 on the machine spitz
built within Poky. For this package a work directory of tmp/work/spitz-poky-linux-gnueabi/linux-rp-2.6.20-r7/
, referred to as WORKDIR
, is created. Within this directory, the source is
unpacked to linux-2.6.20 and then patched by quilt (see Section 3.5.1).
Within the linux-2.6.20 directory,
standard Quilt directories linux-2.6.20/patches
and linux-2.6.20/.pc are created,
and standard quilt commands can be used.
There are other directories generated within WORKDIR. The most important
is WORKDIR/temp/ which has log files for each
task (log.do_*.pid) and the scripts BitBake runs for
each task (run.do_*.pid). The WORKDIR/image/ directory is where make
install places its output which is then split into subpackages
within WORKDIR/install/.
As mentioned previously, this is the core of Poky. It has several important subdivisions:
Contains the *.bbclass files. Class
files are used to abstract common code allowing it to be reused by multiple
packages. The base.bbclass file is inherited by every
package. Examples of other important classes are
autotools.bbclass that in theory allows any
Autotool-enabled package to work with Poky with minimal effort, or
kernel.bbclass that contains common code and functions
for working with the linux kernel. Functions like image generation or
packaging also have their specific class files (image.bbclass
, rootfs_*.bbclass and
package*.bbclass).
This is the core set of configuration files which start from
bitbake.conf and from which all other configuration
files are included (see the includes at the end of the file, even
local.conf is loaded from there!). While
bitbake.conf sets up the defaults, these can often be
overridden by user (local.conf), machine or
distribution configuration files.
Contains all the machine configuration files. If you set MACHINE="spitz", the
end result is Poky looking for a spitz.conf file in this directory. The includes
directory contains various data common to multiple machines. If you want to add
support for a new machine to Poky, this is the directory to look in.
Any distribution specific configuration is controlled from here. OpenEmbedded supports multiple distributions of which Poky is one. Poky only contains the Poky distribution so poky.conf is the main file here. This includes the versions and SRCDATES for applications which are configured here. An example of an alternative configuration is poky-bleeding.conf although this mainly inherits its configuration from Poky itself.
Each application (package) Poky can build has an associated .bb file which are all stored under this directory. Poky finds them through the BBFILES variable which defaults to packages/*/*.bb. Adding a new piece of software to Poky consists of adding the appropriate .bb file. The .bb files from OpenEmbedded upstream are usually compatible although they are not supported.
Table of Contents
Bitbake a program written in Python which interprets the metadata that makes up Poky. At some point, people wonder what actually happens when you type bitbake poky-image-sato. This section aims to give an overview of what happens behind the scenes from a BitBake perspective.
It is worth noting that bitbake aims to be a generic "task" executor capable of handling complex dependency relationships. As such it has no real knowledge of what the tasks its executing actually do. It just considers a list of tasks with dependencies and handles metadata consisting of variables in a certain format which get passed to the tasks.
The first thing BitBake does is work out its configuration by
looking for a file called bitbake.conf.
Bitbake searches through the BBPATH environment
variable looking for a conf/
directory containing a bitbake.conf file and
adds the first bitbake.conf file found in
BBPATH (similar to the PATH environment variable).
For Poky, bitbake.conf is found in meta/conf/.
In Poky, bitbake.conf lists other configuration
files to include from a conf/
directory below the directories listed in BBPATH.
In general the most important configuration file from a user's perspective
is local.conf, which contains a users customized
settings for Poky. Other notable configuration files are the distribution
configuration file (set by the
DISTRO variable) and the machine configuration file
(set by the MACHINE
variable). The
DISTRO and
MACHINE environment variables are both usually set in
the local.conf file. Valid distribution
configuration files are available in the
meta/conf/distro/ directory and valid machine configuration
files in the meta/conf/machine/
directory. Within the
meta/conf/machine/include/ directory are various
tune-*.inc configuration files which provide common
"tuning" settings specific to and shared between particular
architectures and machines.
After the parsing of the configuration files some standard classes
are included. In particular, base.bbclass is
always included, as will any other classes
specified in the configuration using the INHERIT
variable. Class files are searched for in a classes subdirectory
under the paths in BBPATH in the same way as
configuration files.
After the parsing of the configuration files is complete, the
variable BBFILES
is set, usually in
local.conf, and defines the list of places to search for
.bb files. By
default this specifies the meta/packages/
directory within Poky, but other directories such as
meta-extras/ can be included
too. If multiple directories are specified a system referred to as
"collections" is used to
determine which files have priority.
Bitbake parses each .bb file in
BBFILES and
stores the values of various variables. In summary, for each
.bb
file the configuration + base class of variables are set, followed
by the data in the .bb file
itself, followed by any inherit commands that
.bb file might contain.
Parsing .bb files is a time
consuming process, so a cache is kept to speed up subsequent parsing.
This cache is invalid if the timestamp of the .bb
file itself has changed, or if the timestamps of any of the include,
configuration or class files the .bb
file depends on have changed.
Once all the .bb files have been
parsed, BitBake will proceed to build "poky-image-sato" (or whatever was
specified on the commandline) and looks for providers of that target.
Once a provider is selected, BitBake resolves all the dependencies for
the target. In the case of "poky-image-sato", it would lead to
task-oh.bb and task-base.bb
which in turn would lead to packages like Contacts,
Dates, BusyBox
and these in turn depend on glibc and the toolchain.
Sometimes a target might have multiple providers and a common example is "virtual/kernel" that is provided by each kernel package. Each machine will often elect the best provider of its kernel with a line like the following in the machine configuration file:
PREFERRED_PROVIDER_virtual/kernel = "linux-rp"
The default PREFERRED_PROVIDER is the provider with the same name as the target.
Understanding how providers are chosen is complicated by the fact multiple versions might be present. Bitbake defaults to the highest version of a provider by default. Version comparisons are made using the same method as Debian. The PREFERRED_VERSION variable can be used to specify a particular version (usually in the distro configuration) but the order can also be influenced by the DEFAULT_PREFERENCE variable. By default files have a preference of "0". Setting the DEFAULT_PREFERENCE to "-1" will make a package unlikely to be used unless it was explicitly referenced and "1" makes it likely the package will be used. PREFERRED_VERSION overrides any default preference. DEFAULT_PREFERENCE is often used to mark more experimental new versions of packages until they've undergone sufficient testing to be considered stable.
The end result is that internally, BitBake has now built a list of providers for each target it needs in order of priority.
Each target BitBake builds consists of multiple tasks (e.g. fetch, unpack, patch, configure, compile etc.). For best performance on multi-core systems, BitBake considers each task as an independent entity with a set of dependencies. There are many variables that are used to signify these dependencies and more information can be found found about these in the BitBake manual. At a basic level it is sufficient to know that BitBake uses the DEPENDS and RDEPENDS variables when calculating dependencies and descriptions of these variables are available through the links.
Based on the generated list of providers and the dependency information, BitBake can now calculate exactly which tasks it needs to run and in what order. The build now starts with BitBake forking off threads up to the limit set in the BB_NUMBER_THREADS variable as long there are tasks ready to run, i.e. tasks with all their dependencies met.
As each task completes, a timestamp is written to the directory
specified by the STAMPS variable (usually
build/tmp/stamps/*/). On
subsequent runs, BitBake looks at the STAMPS
directory and will not rerun
tasks its already completed unless a timestamp is found to be invalid.
Currently, invalid timestamps are only considered on a per .bb file basis so if for example the configure stamp has a timestamp greater than the
compile timestamp for a given target the compile task would rerun but this
has no effect on other providers depending on that target. This could
change or become configurable in future versions of BitBake. Some tasks
are marked as "nostamp" tasks which means no timestamp file will be written
and the task will always rerun.
Once all the tasks have been completed BitBake exits.
It's worth noting what BitBake does to run a task. A task can either
be a shell task or a python task. For shell tasks, BitBake writes a
shell script to ${WORKDIR}/temp/run.do_taskname.pid
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 is
sent to the file ${WORKDIR}/temp/log.do_taskname.pid.
Looking at the
expanded shell functions in the run file and the output in the log files
is a useful debugging technique.
Python functions are executed internally to BitBake itself and logging goes to the controlling terminal. Future versions of BitBake will write the functions to files in a similar way to shell functions and logging will also go to the log files in a similar way.
To quote from "bitbake --help":
Usage: bitbake [options] [package ...]
Executes the specified task (default is 'build') for a given set of BitBake files.
It expects that BBFILES is defined, which is a space separated list of files to
be executed. BBFILES does support wildcards.
Default BBFILES are the .bb files in the current directory.
Options:
--version show program's version number and exit
-h, --help show this help message and exit
-b BUILDFILE, --buildfile=BUILDFILE
execute the task against this .bb file, rather than a
package from BBFILES.
-k, --continue continue as much as possible after an error. While the
target that failed, and those that depend on it,
cannot be remade, the other dependencies of these
targets can be processed all the same.
-f, --force force run of specified cmd, regardless of stamp status
-i, --interactive drop into the interactive mode also called the BitBake
shell.
-c CMD, --cmd=CMD Specify task to execute. Note that this only executes
the specified task for the providee and the packages
it depends on, i.e. 'compile' does not implicitly call
stage for the dependencies (IOW: use only if you know
what you are doing). Depending on the base.bbclass a
listtasks tasks is defined and will show available
tasks
-r FILE, --read=FILE read the specified file before bitbake.conf
-v, --verbose output more chit-chat to the terminal
-D, --debug Increase the debug level. You can specify this more
than once.
-n, --dry-run don't execute, just go through the motions
-p, --parse-only quit after parsing the BB files (developers only)
-d, --disable-psyco disable using the psyco just-in-time compiler (not
recommended)
-s, --show-versions show current and preferred versions of all packages
-e, --environment show the global or per-package environment (this is
what used to be bbread)
-g, --graphviz emit the dependency trees of the specified packages in
the dot syntax
-I IGNORED_DOT_DEPS, --ignore-deps=IGNORED_DOT_DEPS
Stop processing at the given list of dependencies when
generating dependency graphs. This can help to make
the graph more appealing
-l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS
Show debug logging for the specified logging domains
-P, --profile profile the command and print a reportAs well as the containing the parsing and task/dependency handling code, bitbake also contains a set of "fetcher" modules which allow fetching of source code from various types of sources. Example sources might be from disk with the metadata, from websites, from remote shell accounts or from SCM systems like cvs/subversion/git.
The fetchers are usually triggered by entries in SRC_URI. Information about the options and formats of entries for specific fetchers can be found in the BitBake manual.
One useful feature for certain SCM fetchers is the ability to "auto-update" when the upstream SCM changes version. Since this requires certain functionality from the SCM only certain systems support it, currently Subversion, Bazaar and to a limited extent, Git. It works using the SRCREV variable. See the developing with an external SCM based project section for more information.
Table of Contents
base.bbclassautotools.bbclassupdate-alternatives.bbclassupdate-rc.d.bbclassbinconfig.bbclassdebian.bbclasspkgconfig.bbclasssrc_distribute_local.bbclasscpan.bbclassdistutils.bbclassdevshell.bbclasspackage*.bbclasskernel.bbclassimage.bbclass and rootfs*.bbclasssanity.bbclassinsane.bbclasssiteinfo.bbclass
Class files are used to abstract common functionality and share it amongst multiple
.bb files. Any metadata usually found in a
.bb file can also be placed in a class
file. Class files are identified by the extension
.bbclass and are usually placed
in a classes/ directory beneath the
meta/ directory or the build/ directory in the same way as .conf files in the conf directory. Class files are searched for
in BBPATH in the same was as .conf files too.
In most cases inheriting the class is enough to enable its features, although for some classes you may need to set variables and/or override some of the default behaviour.
The base class is special in that every .bb
file inherits it automatically. It contains definitions of standard basic
tasks such as fetching, unpacking, configuring (empty by default), compiling
(runs any Makefile present), installing (empty by default) and packaging
(empty by default). These are often overridden or extended by other classes
such as autotools.bbclass or
package.bbclass. The class contains some commonly
some commonly used functions such as oe_libinstall
and oe_runmake. The end of the class file has a
list of standard mirrors for software projects for use by the fetcher code.
Autotools (autoconf, automake, libtool) brings standardisation and this class aims to define a set of tasks (configure, compile etc.) that will work for all autotooled packages. It should usualy be enough to define a few standard variables as documented in the simple autotools example section and then simply "inherit autotools". This class can also work with software that emulates autotools.
Its useful to have some idea of the tasks this class defines work and what they do behind the scenes.
'do_configure' regenearates the configure script and then launches it with a standard set of arguments used during cross-compilation. Additional parameters can be passed to configure through the EXTRA_OECONF variable.
'do_compile' runs make with arguments specifying the compiler and linker. Additional arguments can be passed through the EXTRA_OEMAKE variable.
'do_install' runs make install passing a DESTDIR option taking its value from the standard DESTDIR variable.
By default the class does not stage headers and libraries so
the recipe author needs to add their own do_stage()
task. For typical recipes the following example code will usually be
enough:
do_stage() {
autotools_stage_all
}
Several programs can fulfill the same or similar function and they can be installed with the same name. For example the ar command is available from the "busybox", "binutils" and "elfutils" packages. This class handles the renaming of the binaries so multiple packages can be installed which would otherwise conflict and yet the ar command still works regardless of which are installed or subsequently removed. It renames the conflicting binary in each package and symlinks the highest priority binary during installation or removal of packages. Four variables control this class:
Name of binary which will be replaced (ar in this example)
Path to resulting binary ("/bin/ar" in this example)
Path to real binary ("/usr/bin/ar.binutils" in this example)
Priority of binary, the version with the most features should have the highest priority
This class uses update-rc.d to safely install an initscript on behalf of the package. Details such as making sure the initscript is stopped before a package is removed and started when the package is installed are taken care of. Three variables control this class, INITSCRIPT_PACKAGES, INITSCRIPT_NAME and INITSCRIPT_PARAMS. See the links for details.
Before pkg-config became widespread, libraries shipped shell scripts to give information about the libraries and include paths needed to build software (usually named 'LIBNAME-config'). This class assists any recipe using such scripts.
During staging Bitbake installs such scripts into the staging/ directory. It also changes all
paths to point into the staging/
directory so all builds which use the script will use the correct
directories for the cross compiling layout.
This class renames packages so that they follow the Debian naming policy, i.e. 'glibc' becomes 'libc6' and 'glibc-devel' becomes 'libc6-dev'.
Pkg-config brought standardisation and this class aims to make its integration smooth for all libraries which make use of it.
During staging Bitbake installs pkg-config data into the staging/ directory. By making use of
sysroot functionality within pkgconfig this class no longer has to
manipulate the files.
Many software licenses require providing the sources for compiled
binaries. To simplify this process two classes were created:
src_distribute.bbclass and
src_distribute_local.bbclass.
Result of their work are tmp/deploy/source/
subdirs with sources sorted by LICENSE
field. If recipe lists few licenses (or has entries like "Bitstream Vera") source archive is put in each
license dir.
Src_distribute_local class has three modes of operating:
copy - copies the files to the distribute dir
symlink - symlinks the files to the distribute dir
move+symlink - moves the files into distribute dir, and symlinks them back
Recipes for Perl modules are simple - usually needs only pointing to source archive and inheriting of proper bbclass. Building is split into two methods dependly on method used by module authors.
Modules which use old Makefile.PL based build system require
using of cpan.bbclass in their recipes.
Modules which use Build.PL based build system require
using of cpan_build.bbclass in their recipes.
Recipes for Python extensions are simple - usually needs only pointing to source archive and inheriting of proper bbclass. Building is split into two methods dependly on method used by module authors.
Extensions which use autotools based build system require using of autotools and distutils-base bbclasses in their recipes.
Extensions which use distutils build system require using
of distutils.bbclass in their recipes.
This class adds the devshell task. Its usually up to distribution policy to include this class (Poky does). See the developing with 'devshell' section for more information about using devshell.
The packaging classes add support for generating packages from the output
from builds. The core generic functionality is in
package.bbclass, code specific to particular package
types is contained in various sub classes such as
package_deb.bbclass and package_ipk.bbclass.
Most users will
want one or more of these classes and this is controlled by the
PACKAGE_CLASSES
variable. The first class listed in this variable will be used for image
generation. Since images are generated from packages a packaging class is
needed to enable image generation.
This class handle building of Linux kernels and the class contains code to know how to build both 2.4 and 2.6 kernel trees. All needed headers are
staged into STAGING_KERNEL_DIR
directory to allow building of out-of-tree modules using module.bbclass.
The means that each kerel module built is packaged separately and inter-modules dependencies are created by parsing the modinfo output. If all modules are required then installing "kernel-modules" package will install all packages with modules and various other kernel packages such as "kernel-vmlinux" are also generated.
Various other classes are used by the kernel and module classes internally including
kernel-arch.bbclass, module_strip.bbclass,
module-base.bbclass and linux-kernel-base.bbclass.
Those classes add support for creating images in many formats. First the
rootfs is created from packages by one of the rootfs_*.bbclass
files (depending on package format used) and then image is created.
The IMAGE_FSTYPES
variable controls which types of image to generate.
The list of packages to install into the image is controlled by the
IMAGE_INSTALL
variable.
This class checks prerequisite software is present to try and identify and notify the user of problems which will affect their build. It also performs basic checks of the users configuration from local.conf to prevent common mistakes and resulting build failures. Its usually up to distribution policy to include this class (Poky does).
This class adds a step to package generation which sanity checks the packages generated by Poky. There are an ever increasing range of checks this makes, checking for common problems which break builds/packages/images, see the bbclass file for more information. Its usually up to distribution policy to include this class (Poky doesn't at the time of writing but plans to soon).
Autotools can require tests which have to execute on the target hardware. Since this isn't possible in general when cross compiling, siteinfo is used to provide cached test results so these tests can be skipped over but the correct values used. The meta/site directory contains test results sorted into different categories like architecture, endianess and the libc used. Siteinfo provides a list of files containing data relevant to the current build in the CONFIG_SITE variable which autotools will automatically pick up.
The class also provides variables like SITEINFO_ENDIANESS and SITEINFO_BITS which can be used elsewhere in the metadata.
This class is included from base.bbclass and is hence always active.
Poky has several standard images covering most people's standard needs. A full
list of image targets can be found by looking in the
meta/packages/images/ directory. The standard images are listed below
along with details of what they contain:
poky-image-minimal - A small image, just enough to allow a device to boot
poky-image-base - console only image with full support of target device hardware
poky-image-core - X11 image with simple apps like terminal, editor and file manager
poky-image-sato - X11 image with Sato theme and Pimlico applications. Also contains terminal, editor and file manager.
poky-image-sdk - X11 image like poky-image-sato but also include native toolchain and libraries needed to build applications on the device itself. Also includes testing and profiling tools and debug symbols.
meta-toolchain - This generates a tarball containing
a standalone toolchain which can be used externally to Poky. It is self
contained and unpacks to the /usr/local/poky
directory. It also contains a copy of QEMU and the scripts neccessary to run
poky QEMU images.
meta-toolchain-sdk - This includes everything in meta-toolchain but also includes development headers and libraries forming a complete standalone SDK. See the Developing using the Poky SDK and Developing using the Anjuta Plugin sections for more information.
Table of Contents
'Features' provide a mechanism for working out which packages should be included in the generated images. Distributions can select which features they want to support through the DISTRO_FEATURES variable which is set in the distribution configuration file (poky.conf for Poky). Machine features are set in the MACHINE_FEATURES variable which is set in the machine configuration file and specifies which hardware features a given machine has.
These two variables are combined to work out which kernel modules, utilities and other packages to include. A given distribution can support a selected subset of features so some machine features might not be included if the distribution itself doesn't support them.
The items below are valid options for DISTRO_FEATURES.
alsa - ALSA support will be included (OSS compatibility kernel modules will be installed if available)
bluetooth - Include bluetooth support (integrated BT only)
ext2 - Include tools for supporting for devices with internal HDD/Microdrive for storing files (instead of Flash only devices)
irda - Include Irda support
keyboard - Include keyboard support (e.g. keymaps will be loaded during boot).
pci - Include PCI bus support
pcmcia - Include PCMCIA/CompactFlash support
usbgadget - USB Gadget Device support (for USB networking/serial/storage)
usbhost - USB Host support (allows to connect external keyboard, mouse, storage, network etc)
wifi - WiFi support (integrated only)
cramfs - CramFS support
ipsec - IPSec support
ipv6 - IPv6 support
nfs - NFS client support (for mounting NFS exports on device)
ppp - PPP dialup support
smbfs - SMB networks client support (for mounting Samba/Microsoft Windows shares on device)
The items below are valid options for MACHINE_FEATURES.
acpi - Hardware has ACPI (x86/x86_64 only)
alsa - Hardware has ALSA audio drivers
apm - Hardware uses APM (or APM emulation)
bluetooth - Hardware has integrated BT
ext2 - Hardware HDD or Microdrive
irda - Hardware has Irda support
keyboard - Hardware has a keyboard
pci - Hardware has a PCI bus
pcmcia - Hardware has PCMCIA or CompactFlash sockets
screen - Hardware has a screen
serial - Hardware has serial support (usually RS232)
touchscreen - Hardware has a touchscreen
usbgadget - Hardware is USB gadget device capable
usbhost - Hardware is USB Host capable
wifi - Hardware has integrated WiFi
The contents of images generated by Poky can be controlled by the IMAGE_FEATURES variable in local.conf. Through this you can add several different predefined packages such as development utilities or packages with debug information needed to investigate application problems or profile applications.
Current list of IMAGE_FEATURES contains:
apps-console-core - Core console applications such as ssh daemon, avahi daemon, portmap (for mounting NFS shares)
x11-base - X11 server + minimal desktop
x11-sato - OpenedHand Sato environment
apps-x11-core - Core X11 applications such as an X Terminal, file manager, file editor
apps-x11-games - A set of X11 games
apps-x11-pimlico - OpenedHand Pimlico application suite
tools-sdk - A full SDK which runs on device
tools-debug - Debugging tools such as strace and gdb
tools-profile - Profiling tools such as oprofile, exmap and LTTng
tools-testapps - Device testing tools (e.g. touchscreen debugging)
nfs-server - NFS server (exports / over NFS to everybody)
dev-pkgs - Development packages (headers and extra library links) for all packages installed in a given image
dbg-pkgs - Debug packages for all packages installed in a given image
Table of Contents
This section lists common variables used in Poky and gives an overview of their function and contents.
A B C D E F H I K L M P R S T W
E-mail address to contact original author(s) - to send patches, forward bugs...
Use current (newest) source revision - used with SRCREV variable.
Flags passed to C compiler for the target system. Evaluates to the same as TARGET_CFLAGS.
A regular expression which evalutates to match the machines the recipe works with. It stops recipes being run on machines they're incompatible with which is partciuarly useful with kernels. It also helps to to increase parsing speed as if its found the current machine is not compatible, further parsing of the recipe is skipped.
Contains a list of files which containing autoconf test results relevant to the current build. This variable is used by the autotools utilities when running configure.
Location to search for pre-generated tarballs when fetching from remote SCM repositories (CVS/SVN/GIT)
Destination directory
Build packages with debugging information. This influences the value SELECTED_OPTIMIZATION takes.
The options to pass in TARGET_CFLAGS and CFLAGS when compiling a system for debugging. This defaults to "-O -fno-omit-frame-pointer -g".
Priority of recipe
A list of build time dependencies for a given recipe. These indicate recipes that must have staged before this recipe can configure.
Package description used by package managers
Destination directory
Short name of distribution
List of packages required by distribution.
List of packages which extend usability of image. Those packages will be automatically installed but can be removed by user.
Features of the distribution.
Long name of distribution
Version of distribution
Directory where all fetched sources will be stored
list of directories/files which will be placed in packages
The options to pass in TARGET_CFLAGS and CFLAGS when compiling an optimised system. This defaults to "-fexpensive-optimizations -fomit-frame-pointer -frename-registers -O2".
List of features present in resulting images
Formats of rootfs images which we want to have created
List of packages used to build image
This variable causes the build to not strip binaries in resulting packages.
This variable causes the named class to be inherited at this point during parsing. Its only valid in configuration files.
Scope: Used in recipes when using update-rc.d.bbclass. Optional, defaults to PN.
A list of the packages which contain initscripts. If multiple packages are specified you need to append the package name to the other INITSCRIPT_* as an override.
Scope: Used in recipes when using update-rc.d.bbclass. Mandatory.
The filename of the initscript (as installed to ${etcdir}/init.d).
Scope: Used in recipes when using update-rc.d.bbclass. Mandatory.
Specifies the options to pass to update-rc.d. An example is "start 99 5 2 . stop 20 0 1 6 ." which gives the script a runlevel of 99, starts the script in initlevels 2 and 5 and stops it in levels 0, 1 and 6.
Target device
List of packages required to boot device
List of packages required to boot device (usually additional kernel modules)
List of packages required to use device
List of packages useful to use device (for example additional kernel modules)
List of device features - defined in machine features section
E-mail of distribution maintainer
Architecture of resulting package
List of resulting packages formats
List of architectures compatible with device CPU. Usable when build is done for few different devices with misc processors (like XScale and ARM926-EJS)
List of packages to be created from recipe. The default value is "${PN}-dbg ${PN} ${PN}-doc ${PN}-dev"
Name of package.
Revision of package.
Version of package. The default value is "1.0"
Epoch of the package. The default value is "1". The field is used to make upgrades possible when the versioning scheme changes in some backwards incompatible way.
If multiple recipes provide an item, this variable determines which one should be given preference. It should be set to the "$PN" of the recipe to be preferred.
If there are multiple versions of recipe available, this variable determines which one should be given preference. It should be set to the "$PV" of the recipe to be preferred.
Libc implementation selector - glibc or uclibc can be selected.
Toolchain selector. It can be external toolchain built from Poky or few supported combinations of upstream GCC or CodeSourcery Labs toolchain.
List of packages which which conflict with this one. Package will not be installed if they will not be removed first.
A list of run-time dependencies for a package. These packages need to be installed alongside the package it applies to so the package will run correctly, an example is a perl script which would rdepend on perl. Since this variable applies to output packages there would usually be an override attached to this variable like RDEPENDS_${PN}-dev. Names in this field should be as they are in PACKAGES namespave before any renaming of the output package by classes like debian.bbclass.
Size of rootfs in megabytes
List of packages which extend usability of package. Those packages will be automatically installed but can be removed by user.
List of packages which are replaced with this one.
Path to unpacked sources (by default: "${WORKDIR}/${PN}-${PV}")
Section where package should be put - used by package managers
The variable takes the value of FULL_OPTIMIZATION unless DEBUG_BUILD = "1" in which case DEBUG_OPTIMIZATION is used.
Speed and device for serial port used to attach serial console. This is given to kernel as "console" param and after boot getty is started on that port so remote login is possible.
A list of commands to run within the a shell, used by TERMCMDRUN. It defaults to SHELLRCCMD.
How to launch a shell, defaults to bash.
Contains "le" for little-endian or "be" for big-endian depending on the endian byte order of the target system.
Contains "32" or "64" depending on the number of bits for the CPU of the target system.
List of source files (local or remote ones)
By default there is code which automatically detects whether SRC_URI contains files which are machine specific and if this is the case it automatically changes PACKAGE_ARCH. Setting this variable to "0" disables that behaviour.
Date of source code used to build package (if it was fetched from SCM).
Revision of source code used to build package (Subversion, GIT, Bazaar only).
Directory with kernel headers required to build out-of-tree modules.
Directory (usually TMPDIR/stamps) with timestamps of executed tasks.
The architecture of the device we're building for. A number of values are possible but Poky primarily supports "arm" and "i586".
Flags passed to C compiler for the target system. Evaluates to the same as CFLAGS.
Method of handling FPU code. For FPU-less targets (most of ARM cpus) it has to be set to "soft" otherwise kernel emulation will get used which will result in performance penalty.
Type of target operating system. Can be "linux" for glibc based system, "linux-uclibc" for uClibc. For ARM/EABI targets there are also "linux-gnueabi" and "linux-uclibc-gnueabi" values possible.
This command is used by bitbake to lauch a terminal window with a shell. The shell is unspecified so the user's default shell is used. By default it is set to gnome-terminal but it can be any X11 terminal application or terminal multiplexers like screen.
This command is similar to TERMCMD however instead of the users shell it runs the command specified by the SHELLCMDS variable.
Table of Contents
Whilst most variables can be used in almost any context (.conf, .bbclass, .inc or .bb file), variables are often associated with a particular locality/context. This section describes some common associations.
| 8.1. | How does Poky differ from OpenEmbedded? |
Poky is a derivative of OpenEmbedded, a stable, smaller subset focused on the GNOME Mobile environment. Development in Poky is closely tied to OpenEmbedded with features being merged regularly between the two for mutual benefit. | |
| 8.2. | How can you claim Poky is stable? |
There are three areas that help with stability;
| |
| 8.3. | How do I get support for my board added to Poky? |
There are two main ways to get a board supported in Poky;
Usually if it's not a completely exotic board then adding support in Poky should be fairly straightforward. | |
| 8.4. | Are there any products running poky ? |
The Vernier Labquest is using Poky (for more about the Labquest see the case study at OpenedHand). There are a number of pre-production devices using Poky and we will announce those as soon as they are released. | |
| 8.5. | What is the Poky output ? |
The output of a Poky build will depend on how it was started, as the same set of recipes can be used to output various formats. Usually the output is a flashable image ready for the target device. | |
| 8.6. | How do I add my package to Poky? |
To add a package you need to create a bitbake recipe - see the Poky handbook to find out how to create a recipe. | |
| 8.7. | Do I have to reflash my entire board with a new poky image when recompiling a package? |
Poky can build packages in various formats, ipkg, Debian package, or RPM. The package can then be upgraded using the package tools on the device, much like on a desktop distribution like Ubuntu or Fedora. | |
| 8.8. | What is GNOME Mobile? What's the difference between GNOME Mobile and GNOME? |
GNOME Mobile is a subset of the GNOME platform targeted at mobile and embedded devices. The the main difference between GNOME Mobile and standard GNOME is that desktop-orientated libraries have been removed, along with deprecated libraries, creating a much smaller footprint. | |
| 8.9. | How do I make Poky work in RHEL/CentOS? |
To get Poky working under RHEL/CentOS 5.1 you need to first install some required packages. The standard CentOS packages needed are:
On top of those the following external packages are needed:
Once these packages are installed Poky will be able to build standard images however there may be a problem with QEMU segfaulting. You can either disable the generation of binary locales by setting ENABLE_BINARY_LOCALE_GENERATION to "0" or remove the linux-2.6-execshield.patch from the kernel and rebuild it since its that patch which causes the problems with QEMU. | |
| 8.10. | I see lots of 404 responses for files on http://folks.o-hand.com/~richard/poky/sources/*. Is something wrong? |
Nothing is wrong, Poky will check any configured source mirrors before downloading from the upstream sources. It does this searching for both source archives and pre-checked out versions of SCM managed software. This is so in large installations, it can reduce load on the SCM servers themselves. The address above is one of the default mirrors configured into standard Poky so if an upstream source disappears, we can place sources there so builds continue to work. | |
| 8.11. | I have a machine specific data in a package for one machine only but the package is being marked as machine specific in all cases, how do I stop it? |
Set SRC_URI_OVERRIDES_PACKAGE_ARCH = "0" in the .bb file but make sure the package is manually marked as machine specific in the case that needs it. The code which handles SRC_URI_OVERRIDES_PACKAGE_ARCH is in base.bbclass. |
Table of Contents
We're happy for people to experiment with Poky and there are a number of places to find help if you run into difficulties or find bugs. To find out how to download source code see the Obtaining Poky section of the Introduction.
Problems with Poky should be reported in the bug tracker.
To subscribe to the mailing list send mail to:
poky+subscribe <at> openedhand <dot> com
Then follow the simple instructions in subsequent reply. Archives are available here.
OpenedHand - The company behind Poky.
OpenEmbedded - The upstream generic embedded distribution Poky derives from (and contributes to).
Bitbake - The tool used to process Poky metadata.
Pimlico - A suite of lightweight Personal Information Management (PIM) applications designed primarily for handheld and mobile devices.
QEMU - An open source machine emulator and virtualizer.
OpenedHand Ltd
Unit R, Homesdale Business Center
216-218 Homesdale Rd
Bromley, BR1 2QZ
England
+44 (0) 208 819 6559
info@openedhand.com