Introduction to OpenEmbedded

An Embedded Linux Distribution Framework

Khem Raj

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Agenda

Introduction

Features

Getting OE

Layout

Bitbake

Building OE

A bit more on features

Adding new package

Rundown

FAQ & QA

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What is OpenEmbedded ?

Framework to build Embedded Linux distributions

Meta-data describing how to build software Includes tools to help build various RFS types. Learn more at http://www.openembedded.org http://wiki.openembedded.net/index.php/Mailing

_lists IRC channel #oe on irc.freenode.net

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OpenEmbedded In Action

Many popular distributions based on OE MontaVista Linux 6 Palm WebOS ( Palm PRE) OpenZaurus Ångström Poky ( Garmin uses poky) http://wiki.openembedded.net/index.php/Success_s

tories

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Features

Builds complete system includes toolchains, SDK, root file system and applications.

Fine granularity in packaging (-dev, -dbg, locale)

Supports Many popular architectures ARM, PowerPC, SH, MIPS, x86, x86-64

Machine specific tuning Supports package management (rpm,

deb, ipk)

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More Features ...

Console, OPIE, GPE, Gnome, etc. GUI tools Qt/Qte, GTK+, tk Choices of packages Varied development tools QA, Tinderbox, insane class, Sepukku, fail-fast Distributed compiling (icecc)

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Prerequisites

Workstation with a lot of RAM :) A large free space on hard-disk (~10G)

Can be less with rm_work feature

Install required software for build machine Internet Connection

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Getting OpenEmbedded

Uses GIT for SCM Cloning the metadata & bitbake

git clone git://git.openembedded.org/openembedded

org.openembedded.dev – Master Stable/2009 – Stable release branch User branches

git clone git://git.openembedded.net/bitbake

You can use master branch

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Meta-data layout

Classes – common tasks and properties Conf – Machine, distribution configurations Docs – Documentation Files – Device table additions MAINTAINERS – List of people responsible Recipes – The metadata to build a package Site – cached autoconf variables Contrib: Contributed scripts and

goodies

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${TMPDIR} layout

TMPDIR denote the working directory used by bitbakecache/

cross/ - Cross tools gcc etc.

deploy/

images/ – Final images e.g. tar, ext2, kernel, uboot

ipk/ – individual packages

staging/ – area to have installations used in build

stamps/ - Time stamps for bitbake

work/ - The build trees for recipes all objects etc.

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Bitbake

Simple tool to execute tasks on meta-data at the heart of OE

Parse recipes Package graph Task graph .conf, .bb, .inc .bbclass files Non executable data e.g. variable

assignment Executable tasks e.g. do_compile

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Bitbake ...

Bitbake parses classes, recipes and conf files For every task there is a shell script generated

and executed Common tasks e.g. fetch unpack etc. packaging tasks – package, package_write_ipk build tasks – configure, compile etc

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Bitbake ...

List of tasks

bitbake -c listtasks hello

do_build

do_fetch

...

Bitbake user Manual at http://bitbake.berlios.de/manual/

More about bitbake some other day

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Useful bitbake operations

Bitbake -c listtasks <recipe>

bitbake -c fetch_all

bitbake -c devshell <recipe>

bitbake helloworld-image

bitbake console-image

bitbake x11-image

bitbake package-index

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Setting up Environment

http://wiki.openembedded.net/index.php/OEandYourDistro

Sanity checkers complains about missing required packages on build machine.

Wide choice of build distributions e.g. debian, ubuntu, gentoo, Fedora, SuSE and much more

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local.conf

Use conf/local.conf.sample as starting point You can pin version numbers and preferred

providers Enable services like QA, tinderbox, devshell Parallel build Add extra packages to image

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local.conf

MACHINE – Machine to build for e.g. qemuarm DISTRO – Selects distributions e.g. minimal TMPDIR – Temp directory for building DEPLOY_DIR – Directory to contain images IMAGE_FSTYPES – File system types e.g.

jffs2 DL_DIR – Place for tar files PARALLEL_MAKE BB_NUMBER_THREADS

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Building OpenEmbedded

Uses bitbake build tool bitbake console-image

Wait for build to finish .. The results are in ${TMPDIR}/deploy

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In the backgroud

Build some -native packages for build machine

autotools, coreutils etc.

Cross-compiler Essential packages e.g. linux-kernel-headers Other target packages needed for the image image

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OE Variables

There are many variables to control the OE and bitbake functionality

Defined in .conf files most important one is conf/bitbake.conf

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Classes

Base – common functions calls make Autotools – configure and install tasks Kernel – Tasks to compile kernel and modules Module – Tasks to compile external kernel

modules Debian – package naming based on SONAME Etc...

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Packaging

Package utility puts together files needed to be shipped in a package

PACKAGES variable defines what to build FILES_<packages> defines what files are part

of a package Rootfs installs the complete root file system and

packages it into a flashable file system Support cramfs, jffs2, ext2fs, squashfs

ubifs, tar

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Package support

Many packages supported (over 8200 recipes) Supports uclibc, glibc, eglibc, klibc Network applications Console utilities Window managers Development tools

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Updating device

Package repositories can be published as feeds with opkg installed on the device

Feeds are configured in /etc/opkg on device

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OE Tasks

Found in recipes/tasks They are virtual packages One task can inherit another task Common tasks

task-bootstrap

task-base

task-boot

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OE images

A set of packages as a virtual package Image rules are under recipes/images Various formats for packaing e.g. tar Commonly used images

console-image

helloworld-image

x11-image

opie-image

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Overlay

Provides layer where user can add own recipes and configs or redefine existing one

Specify using BBPATH e.g. export BBPATH=${OE_DIR}/overlay:${OE_DIR}/openembedded

Overlay directory contains Conf/ which has any redefined configurations Recipes/ - New or redefines recipes

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Adding new recipe

Create a directory to hold the new recipe files mkdir recipes/hello

Edit the recipe for new application vi recipes/hello/hello_2.5.bb

Add DESCRIPTION, HOMEPAGE LICENSE Locate the download URL and add to SRC_URI

SRC_URI =

“${GNU_MIRROR}/hello/hello-${PV}.tar.gz”

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Adding new recipe ...

bitbake hello This will fail because we do not have MD5/SHA

checksums yet. But... it will generate the required checksums for

you

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Adding New Recipe ...

Add the proper checksums to bb file. Redo bitbake hello Define the real source directory

S = “${WORKDIR}/hello-2.5” Inherit autoools for packages using autotools Customize various build steps by prepending

and appending

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Adding New Recipe

Finished Recipe

bitbake -c clean hello; bitbake hello

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Adding a New machine

Its easy ! Use existing board close to your machine

Create a conf/machine/yourmachine.conf Size of root flash image Type of root file system Kernel Console information MACHINE_FEATURES TARGET_ARCH Tuning for sub-arch

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Adding a new DISTRO

You can add your own distribution Add it under conf/distro/yourdistro.conf Define

DISTRO_NAME, DISTRO_VERSION

Package format e.g. INHERIT += “package_ipk”

LIBC

TARGET_OS

TARGET_FPU

PREFERRED_PROVIDERS

PREFERRED_VERSIONS

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FAQ

Its too slow, can I improve that ? Use BBMASK to mask out packages

How can I create multiple packages from a bb Use PACKAGES and FILES_<packages>

How can I apply patch only for a given machine Use overrides

My package needs a cross tool that you don't have Add native package for it

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Rundown

Make build area

mkdir ${HOME}/oe;cd ${HOME}/oe Install required packages on build system Checkout OE and bitbake

git clone git://git.openembedded.org/openembedded

git://git.openembedded.net/bitbake

Takes around 5-15 mins, depends upon how big hose is running into your computer.

Meta-data should be in ${HOME}/oe/openembedded

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Rundown ...

Create build directory

mkdir ${HOME}/oe/build

Create setup.sh in ${HOME}/oe/build

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Rundown ...

Create local.conf in ${HOME}/oe/build

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Rundown ...

Setup Environment

$ source ${HOME}/oe/build/setup.sh Build an image

bitbake console-image Wait for build to churn

Images are in ${HOME}/oe/build/deploy

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Rundown ...

Boot it up in QEMUqemu-system-arm -M versatilepb --snapshot -gdb tcp::1234 -m 256 -kernel /scratch/oe/qemuarm/deploy/eglibc/images/qemuarm/zImage-qemuarm.bin -hda /scratch/oe/qemuarm/deploy/eglibc/images/qemuarm/console-image-qemuarm.ext2 -usb -usbdevice wacom-tablet -nographic --no-reboot -localtime -append 'console=ttyAMA0 console=ttyS0 root=/dev/sda rw debug user_debug=-1' -net none

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Rundown ...

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Future

BBCLASSEXTEND Sysroot-ing the native packages Moving cross-toolchains under native sysroot Removal of obsoleted packages