Ubuntu Wiki

This page describe the process to build a root filesystem for an armel target (ARM based) device from scratch using a builder script.

Note the Jaunty repository is still going through many changes so your build may fail

Using the builder script

A script that automates this process in ubuntu jaunty (9.04) was created by the ubuntu mobile team, it can be downloaded

Download Script HERE

• Note: this script requires the most recent debootstrap version from ubuntu jaunty.

You will need to install on your Ubuntu machine:

• qemu

• debootstrap_1.0.10ubuntu3_all.deb or newer

The following example will create a tarball of xubuntu-desktop based image for your target device (i.e. a beagleboard):

sudo ./build-arm-rootfs --fqdn beagleboard --login ubuntu --password temppwd --imagesize 2G --seed xubuntu-desktop

The following example will create a tarball of ubuntu-desktop based image for your target device:

sudo ./build-arm-rootfs --fqdn ubuntu --login ubuntu --password ubuntu --imagesize 3G --seed ubuntu-desktop

The options --fqdn (or -f), --login (or -l) and --password (-p) are required for the initial setup. Calling the script with --help shows you all the additional options that can be used to change the setup of the created rootfs.

• Recommendation: Don't pick a serious password if you plan to install this rootfs on other systems as well, rather pick something trivial and change your user password after the first login.

Building a qemu-only image

In case you want to just create an image for usage with qemu instead of building a rootfs tarball, the build-armel-rootfs script has the --notarball option, just call it like below and you will get a qemu image for usage with qemu-system-arm

sudo ./build-arm-rootfs --fqdn qemu-test --login qemu --password qemupwd --notarball

Settings

It is usually not necessary to set any additional options, things like the locale, keyboard setup and timezone will be automatically determined from the building host and will just be set accordingly in your target system, use the script options if you want any of these settings to differ from the build machine.

Typical images (example settings):

To build a xubuntu-desktop image use the following options:

--imagesize 2G --seed xubuntu-desktop

For an ubuntu-desktop image (a similar size is needed if you want a kubuntu image):

--imagesize 3G --seed ubuntu-desktop

A typical remote development comandline environment if you run an armel board headless (note that you should edit /etc/network/interfaces and set up your network device on first login for this):

--imagesize 3G --seed build-essential,openssh-server

A very light desktop (lxde):

--seed lxde,gdm

Creating qemu image from rootfs.tgz

If you don't want to use the --notarball option as described above but want to manually create a qemu Image from a tgz file containing a roofs you can do the following:

After creating the arm rootfs using the builder script, you will get two files:

• build-arm-rootfs-<datetime>.log (contains the build log)

• armel-rootfs-<datetime>.tgz (the rootfs)

To create qemu image from this rootfs file:

• 1) Create the blank image file using dd. In this example, I made a 1GB image. You can change count=3072 for 3GB or count=2048 for 2GB image file.

   dd if=/dev/zero of=ubuntu-arm.img bs=1MB count=1024

  2) Create linux filesystem on the newly created image:

   sudo mke2fs -F -m 0 -b 1024 ubuntu-arm.img 

  3) Loop mount the new image:

   mkdir myqemu
   sudo mount -t ext2 -o loop ubuntu-arm.img myqemu

  4) Extract the rootfs tarball inside the mounted dir (use -p to preserve permissions):

   cd myqemu
   sudo tar zxpf ../armel-rootfs-200904151837.tgz 
   cd ..
   sudo umount myqemu

  5) Now you are set and ready to use the ubuntu-arm.img

   sudo qemu-system-arm -M versatilepb -kernel ./vmlinuz-2.6.28-versatile -hda ubuntu-arm.img -m 256 -append "root=/dev/sda mem=256M ro"

Using a qemu image

If you created your qemu image and want to start a work environment (to compile packages or build applications), grab the kernel from:

qemu kernel

and start qemu with the following command (indeed, you need to adjust the rootfs img name to whatever your image is called)

sudo qemu-system-arm -M versatilepb -kernel ./vmlinuz-2.6.28-versatile -hda arm-rootfs.img -m 256 -append "root=/dev/sda mem=256M ro"

In the booted image you can then log in with the user and password you defined during image creation.

• To be able to copy files from or to the host system it is helpful to install openssh-server on the host and use the scp command inside qemu.

Bugs and Problems

If you run into any problems, please contact "ogra" in #ubuntu-arm on irc.freenode.net or send a mail to ogra@ubuntu.com

If you run into an error please keep the log of your failed build

A known issue is that language-pack handling is not implemented yet, please install the packages for your language manually post install.