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Kernel and Rootfs Build System

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Contents

Overview

Open Embedded (OE) is a Linux distribution for small computers. It is essentially a set of python scripts and package metadata used to evaluate dependencies and build binaries. The OE community is fairly large and the number of target devices and available packages is also fairly large. Poky Linux is a reduction of the packages and target machines to a known, stable set that is well maintained. While it offers less variety than OE, it works more consistently and has clear documentation. In most cases they can be considered interchangeable as the metadata and tools (bitbake) is the same with both projects.

Note

Recently we have begun providing pre-built packages for many common applications and libraries. These packages are available in our package repository. You may find that what you need already exists and do not need to build it from sources.

External Resources

Open Embedded Wiki: http://oe.linuxtogo.org/

Poky Linux Website: http://www.pokylinux.org/

Embedded Linux Blog Planet: http://planet.linuxtogo.org/

An assortment of OpenEmbedded tips: http://www.uv-ac.de/openembedded/openembedded-11.html

OpenMoko Wiki: http://wiki.openmoko.org/wiki/OpenEmbedded

Setup

System Requirements

Currently we test on Gentoo and Ubuntu 8.04 GNU/Linux. Support is claimed for other distros.

There is a minimal set of packages required to run OE/Poky. The system will tell you what it's missing when you run it. More information is available here.

  • Ubuntu 
sudo apt-get install gawk diffstat help2man texi2html texinfo build-essential subversion cvs unzip texinfo git-core

Also on Ubuntu, you need to switch /bin/sh so that it points to /bin/bash rather than /bin/dash: 

sudo dpkg-reconfigure dash

and choose "<No>" from the menu. (dash is the default in Ubuntu, but newer versions of Poky's sanity check warn about this: Using dash as /bin/sh causes various subtle build problems, please use bash instead.).

  • Fedora 
yum install  help2man texi2html

Install

Source Branch

The sources and build scripts you will want depend on what you want to build. For an R1.4.x compatible build, you can either build from a release tag, which is known to work, or from TRUNK of the R1.4.x release. You can also check out code for R1.5, our next major release, but things may or may not build properly, as there are still many changes happening. Select the most appropriate SVN URL from the following table:

Description SVN URL
R1.4.3 Production Release svn://bugcamp.net/bug/tags/releases/R1.4.3/com.buglabs.build.oe
RC 1.4.1.6 (Release R1.4.1 RC 6) svn://bugcamp.net/bug/tags/RCs/R1.4.1/RC1.4.1.6/com.buglabs.build.oe
R1.4.x Development Build svn://bugcamp.net/bug/branches/R1.4/qa/com.buglabs.build.oe
Branch containing extra repos: svn://bugcamp.net/bug/branches/R1.4/extras-repo/com.buglabs.build.oe


Checkout which ever version you need of com.buglabs.build.oe from bugcamp.net, for example R1.4.3 (the last release before moving on to the new bugbase): 

svn co svn://bugcamp.net/bug/tags/releases/R1.4.3/com.buglabs.build.oe

You'll find a directory meta-bug which contains all the build scripts (metadata) that are BUG specific. The other directories are general Poky directories. Keeping our stuff separate helps when we need to upgrade or change out various parts.

Poky-QEMU

If you would like to use the QEMU emulator, you will need a patched version. For Debian/Ubuntu systems, add the appropriate repository to your /etc/apt/sources.list file Then 

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install poky-scripts

Build

The steps below outline how to build the standard BUG Rootfs for R1.3. If you want to add additional packages, or change some of the configurations, please see the information about Tweaking Your Build.

Preparing For a Build

Begin by setting the environment variables. This primarily means the $BBPATH, and on Ubuntu systems the mmap_min_addr

On all systems begin by setting the $BBPATH. Change into the directory where you checked out com.buglabs.build.oe above, and do: 

source reinstate-build-env

On Ubuntu systems, reset mmap_min_addr to 0 (without this you will get an error trying to build ecj). 

sudo -i
echo 0 > /proc/sys/vm/mmap_min_addr

You will need to do that every time you turn your machine on, which might not be such a bad thing as it's a potential security risk to leave it like that. However if you want to make it stick you can:

  • On 8.04: edit /etc/sysctl.conf and change the mmap_min_addr value to 0.
  • On 8.10: create /etc/sysctl.d/60-forbug.conf and put this in it: 
vm.mmap_min_addr=0
Once you've saved the file, execute the following command: 
invoke-rc.d procps start

BUG Kernel

You can see our kernel package in the meta-bug directory: 

$ ls meta-bug/packages/linux/
linux-bug-2.6.19.2  linux-bug-2.6.24.4  linux-bug.inc  linux-bug_2.6.19.2.bb  linux-bug_2.6.24.4.bb

The .inc file is the base "recipe" or configuration file for the kernel. Executing bitbake with the package name will generate the kernel: 

bitbake linux-bug

The binary image is available in your temp directory: 

$ ls build/tmp/deploy/images/
modules-2.6.19.2-bug.tgz  zImage-2.6.19.2-bug-20080528151613.bin  zImage-bug.bin

Building Java

CacaoVM & GNU Classpath

This is a replacement for PhoneME, based off Java SE, it is a package provided by OpenEmbedded

Required packages on Ubuntu: 

 sudo apt-get install gawk diffstat help2man texi2html texinfo build-essential

Potential Problems & Their Solutions:

  • ERROR: Nothing PROVIDES 'cacao' (but '[]' DEPENDS on or otherwise requires it)
    • Solution: source reinstate-build-env
    • Check build/conf/local.conf for 
BBFILES = "\
   ${OEROOT}/meta/packages/*/*.bb \
   ${OEROOT}/meta-bug/packages/*/*.bb \
   ${OEROOT}/meta-oe/packages/*/*.bb \
   ${OEROOT}/meta-jalimo/packages/*/*.bb \
   "
  • ERROR: Could not inherit file classes/qt3x11.bbclass while parsing /home/kschultz/kgilmer/com.buglabs.build.oe/meta-oe/packages/qt/qt-x11-free_3.3.6.bb
    • Solution: source reinstate-build-env
  • ERROR: system_mmap_anonymous: mmap failed: Permission denied
    • Solution: 
sudo -i
$echo 0 > /proc/sys/vm/mmap_min_addr

PhoneME

PhoneME is a package provided by us. It's in the meta-bug directory: 

$ ls meta-bug/packages/phoneme-advanced/
phoneme-advanced-foundation_0.0.bb  phoneme-advanced-personal_0.0.bb  phoneme-advanced.inc

There are two recipes: foundation and personal. To build the headless JVM simply run: 

bitbake phoneme-advanced-foundation

For the full Phoneme Advanced stack 

bitbake phoneme-advanced-personal

Concierge

To build Java packages such as Concierge other recipies are required. Jalimo is a project that is working to bring more Java stuff into Open Embedded. We fetch it as meta-jalimo.

You should be able to build Java packages such as Concierge: 

$ bitbake concierge

Execute OSGI with: 

cd /opt/concierge
cacao -cp concierge.jar:ch.ethz.iks.concierge.framework.jar ch.ethz.iks.concierge.framework.Framework

Complete Rootfs

The recipe that defines the root filesystem for the production bug is called: 

bug-image-production

The recipie that defines the root filesystem for the testing bug is called: 

bug-image-testing

They both live in the images directory in the bug metadata section: 

[POKY ROOT]/meta-bug/packages/images

To build the full production root filesystem, simply run bitbake with the image name: 

$ bitbake bug-image-production

Putting the Rootfs and Kernel onto your BUG

You now have several choices as to the means of deployment for your rootfs and kernel image. The latter is a touch harder to deploy, but see the Poky Deployment wiki about how to do this.

Run Kernel and Root Filesystem in QEMU

If you haven't downloaded the poky scripts for qemu, please see Downloading and Using Prebuilt Images on the poky site. The instructions there apply just to getting the tools. You'll need to set up your repositories (if you use debian) and 

sudo apt-get install qemu poky-scripts

You will also want the poky/qemu kernel, as our kernel may be incompatible with qemu. Download the Kernel Image and run qemu in the form poky-qemu zImage-2.6.23-pinky-3.1-qemuarm.bin <rootfs image> 

$ poky-qemu path/to/zImage-2.6.23-pinky-3.1-qemuarm.bin tmp/deploy/images/bug-image-production-bug-<date-time>.rootfs.ext2

Networking in QEMU

Off the bat you're probably going to want to get networking set up so you don't have to use the terminal and its tiny font. This is taken from the Poky Handbook... 

above not tested yet with this exact config.  jconnolly 02:41, 6 August 2008 (UTC)

Host Setup

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 on your host system 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, created by QEMU as the virtual interface, will be up everytime you run QEMU and it will have network/internet access.

BUG emulated environment

Under emulation there are two steps to configure for internet access via tap0. The first step is to configure routing: 

ifconfig eth0 up
ifconfig eth0 192.168.7.200
route add default gw 192.168.7.1

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, or pass an external dns, like 4.2.2.2 

echo "nameserver     4.2.2.2">>/etc/resolv.conf


Notes and Tips

Bitbake Tips

Debugging

To see the contents of all bitbake variables: 

$ bitbake -e

To run bitbake on a particular bb recipe, use 

$ bitbake -b path/to/recipe.bb

This is especially helpful in debugging, as is the devshell...

To run bitbake in interactive mode (devshell): 

$ bitbake [recipe name] -c devshell

phoneME SVN

There seems to be a problem with the phoneME svn and authentication sessions. To get around this you can either modify your phoneme-advanced.inc SRC_URI flag to log in using your SVN credentials: 

svn://username:password@phoneme.dev.java.net/svn/phoneme/builds/phoneme_advanced-mr2-dev-${PR};module=cdc;proto=https;rev=${SVN_REV};localdir=cdc \

or log into the svn server prior to running the bitbake script. This does some svn session handling magic behind the scenes and everything works okay. More info, see here about a similar issue with the Gumstix team:

http://www.nabble.com/OpenEmbedded-and-I2C-IO-td15622831.html

QEMU & OpenVPN

There is a conflict with using qemu and openvpn simultaneously. Namely, that openvpn owns /dev/net/tun while it's running. A sample error message: 

$ sudo poky-qemu tmp/deploy/images/zImage-qemuarm.bin tmp/deploy/images/poky-image-sato-bug.ext2
Warning: distccd not present, no distcc support loaded.
Running qemu-system-arm using sudo...
/usr/bin/qemu-system-arm -kernel tmp/deploy/images/zImage-qemuarm.bin -net nic,vlan=0 -net  tap,vlan=0,ifname=tap0,script=/usr/share/poky-scripts/poky-qemu-ifup,downscript=/usr/share/poky-scripts/poky- qemu-ifdown -M versatilepb -hda tmp/deploy/images/poky-image-sato-bug.ext2 -usb -usbdevice wacom-tablet -no-reboot  --append root=/dev/sda console=ttyAMA0 console=tty0 mem=64M
warning: could not configure /dev/net/tun: no virtual network emulation
Could not initialize device 'tap'

As a workaround, you'll have to stop openvpn 

$ sudo /etc/init.d/openvpn stop
$ sudo tunctl -d tap0

Letting QEMU create interface tap0. You can also change the interface that QEMU creates, probably to tap1. You'll have to do more work for that though.

U-Boot compilation issues on Gentoo

These instructions also fix u-boot build issues on Ubuntu 9.04

The u-boot sources we used have some code that fails to compile on Gentoo systems, and maybe others. Go to the u-boot-1.3.2+svnr9272-r5 source tree, and edit fdt.h so that the top looks like this: 

#ifndef _FDT_H
#define _FDT_H 

#ifndef __ASSEMBLY__

#include <stdint.h>

struct fdt_header {
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