Category Archives: Ubuntu Touch

Your own Ubuntu Touch image server

Ubuntu Touch images

For those not yet familiar with this, Ubuntu Touch systems are setup using a read-only root filesystem on top of which writable paths are mounted using bind-mounts from persistent or ephemeral storage.

The default update mechanism is therefore image based. We build new images on our build infrastructure, generate diffs between images and publish the result on the public server.

Each image is made of a bunch of xz compreseed tarballs, the actual number of tarballs may vary, so can their name. At the end of the line, the upgrader simply mounts the partitions and unpacks the tarball in the order it’s given them. It has a list of files to remove and the rest of the files are simply unpacked on top of the existing system.

Delta images only contain the files that are different from the previous image, full images contain them all. Partition images are stored in binary format in a partitions/ directory which the upgrader checks and flashes automatically.

The current list of tarballs we tend to use for the official images are:

  • ubuntu: Ubuntu root filesystem (common to all devices)
  • device: Device specific data (partition images and Android image)
  • custom: Customization tarball (applied on top of the root filesystem in /custom)
  • version: Channel/device/build metadata

For more details on how this all works, I’d recommend reading our wiki pages which act as the go-to specification for the server, clients and upgrader.

Running a server

There are a lot of reasons why you may want to run your own system-image server but the main ones seem to be:

  • Supporting your own Ubuntu Touch port with over-the-air updates
  • Publishing your own customized version of an official image
  • QA infrastructure for Ubuntu Touch images
  • Using it as an internal buffer/mirror for your devices

Up until now, doing this was pretty tricky as there wasn’t an easy way to import files from the public system-image server into a local one nor was there a simple way to replace the official GPG keys by your own (which would result in your updates to be considered invalid).

This was finally resolved on Friday when I landed the code for a few new file generators in the main system-image server branch.

It’s now reasonably easy to setup your own server, have it mirror some bits from the main public server, swap GPG keys and include your local tarballs.

Before I start with step by step instructions, please note that due to bug 1278589, you need a valid SSL certificate (https) on your server. This may be a problem to some porters who don’t have a separate IP for their server or can’t afford an SSL certificate. We plan on having this resolved in the system-image client soon.

Installing your server

Those instructions have been tried on a clean Ubuntu 13.10 cloud instance, it assumes that you are running them as an “ubuntu” user with “/home/ubuntu” as its home directory.

Install some required packages:

sudo apt-get install -y bzr abootimg android-tools-fsutils 
    python-gnupg fakeroot pxz pep8 pyflakes python-mock apache2

You’ll need a fair amount of available entropy to generate all the keys used by the test suite and production server. If you are doing this for testing only and don’t care much about getting strong keys, you may want to install “haveged” too.

Then setup the web server:

sudo adduser $USER www-data
sudo chgrp www-data /var/www/
sudo chmod g+rwX /var/www/
sudo rm -f /var/www/index.html
newgroups www-data

That being done, now let’s grab the server code, generate some keys and run the testsuite:

bzr branch lp:~ubuntu-system-image/ubuntu-system-image/server system-image
cd system-image
cp -R tests/keys/*/ secret/gpg/keys/

Now all you need is some configuration. We’ll define a single “test” channel which will contain a single device “mako” (nexus4). It’ll mirror both the ubuntu and device tarball from the main public server (using the trusty-proposed channel over there), repack the device tarball to swap the GPG keys, then download a customization tarball from an http server, stack a keyring tarball (overriding the keys in the ubuntu tarball) and finally generating a version tarball. This channel will contain up to 15 images and will start at image ID “1”.

Doing all this can be done with that bit of configuration (you’ll need to change your server’s FQDN accordingly) in etc/config:

base_path = /home/ubuntu/system-image/
channels = test
gpg_key_path = secret/gpg/keys/
gpg_keyring_path = secret/gpg/keyrings/
publish_path = /var/www/
state_path = state/
public_fqdn =
public_http_port = 80
public_https_port = 443

type = auto
versionbase = 1
fullcount = 15
files = ubuntu, device, custom-savilerow, keyring, version
file_ubuntu = remote-system-image;;trusty-proposed;ubuntu
file_device = remote-system-image;;trusty-proposed;device;keyring=archive-master
file_custom-savilerow = http;;name=custom-savilerow,monitor=
file_keyring = keyring;archive-master
file_version = version

Lastly we need to actual create the channel and device in the server, this is done by calling “bin/si-shell” and then doing:

pub.create_device("test", "mako")
for keyring in ("archive-master", "image-master", "image-signing", "blacklist"):

And that’s it! Your server is now ready to use.
To generate your first image, simply run “bin/import-images”.
This will take a while as it’ll need to download files from those external servers, repack some bits but once it’s done, you’ll have a new image published.

You’ll probably want to run that command from cron every few minutes so that whenever any of the referenced files change a new image is generated and published (deltas will also be automatically generated).

To look at the result of the above, I have setup a server here:

To use that server, you’d flash using: phablet-flash ubuntu-system –alternate-server –channel test

Posted in Canonical voices, Planet Ubuntu, Ubuntu Touch | Tagged | 5 Comments

LXC 1.0: Some more advanced container usage [4/10]

This is post 4 out of 10 in the LXC 1.0 blog post series.

Running foreign architectures

By default LXC will only let you run containers of one of the architectures supported by the host. That makes sense since after all, your CPU doesn’t know what to do with anything else.

Except that we have this convenient package called “qemu-user-static” which contains a whole bunch of emulators for quite a few interesting architectures. The most common and useful of those is qemu-arm-static which will let you run most armv7 binaries directly on x86.

The “ubuntu” template knows how to make use of qemu-user-static, so you can simply check that you have the “qemu-user-static” package installed, then run:

sudo lxc-create -t ubuntu -n p3 -- -a armhf

After a rather long bootstrap, you’ll get a new p3 container which will be mostly running Ubuntu armhf. I’m saying mostly because the qemu emulation comes with a few limitations, the biggest of which is that any piece of software using the ptrace() syscall will fail and so will anything using netlink. As a result, LXC will install the host architecture version of upstart and a few of the networking tools so that the containers can boot properly.

stgraber@castiana:~$ file /bin/ls
/bin/ls: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, """BuildID[sha1]""" =e50e0a5dadb8a7f4eaa2fd715cacb9842e157dc7, stripped
stgraber@castiana:~$ sudo lxc-start -n p3 -d
stgraber@castiana:~$ sudo lxc-attach -n p3
root@p3:/# file /bin/ls
/bin/ls: ELF 32-bit LSB  executable, ARM, EABI5 version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, """BuildID[sha1]""" =88ff013a8fd9389747fb1fea1c898547fb0f650a, stripped
root@p3:/# exit
stgraber@castiana:~$ sudo lxc-stop -n p3


As we know people like to script their containers and that our configuration can’t always accommodate every single use case, we’ve introduced a set of hooks which you may use.

Those hooks are simple paths to an executable file which LXC will run at some specific time in the lifetime of the container. Those executables will also be passed a set of useful environment variables so they can easily know what container invoked them and what to do.

The currently available hooks are (details in lxc.conf(5)):

  • lxc.hook.pre-start (called before any initialization is done)
  • lxc.hook.pre-mount (called after creating the mount namespace but before mounting anything)
  • lxc.hook.mount (called after the mounts but before pivot_root)
  • lxc.hook.autodev (identical to mount but only called if using autodev)
  • lxc.hook.start (called in the container right before /sbin/init)
  • (run after the container has been shutdown)
  • lxc.hook.clone (called when cloning a container into a new one)

Additionally each network section may also define two additional hooks:

  • (called in the network namespace after the interface was created)
  • (called in the network namespace before destroying the interface)

All of those hooks may be specified as many times as you want in the configuration so you can use each hooking point multiple times.

As a simple example, let’s add the following to our “p1” container:

lxc.hook.pre-start = /var/lib/lxc/p1/

And create the hook itself at /var/lib/lxc/p1/

echo "arguments: $*" > /tmp/test
echo "environment:" >> /tmp/test
env | grep LXC >> /tmp/test

Make it executable (chmod 755) and then start the container.
Checking /tmp/test you should see:

arguments: p1 lxc pre-start

Android containers

I’ve often been asked whether it was possible to run Android in an LXC container. Well, the short answer is yes. However it’s not very simple and it really depends on what you want to do with it.

The first thing you’ll need if you want to do this is get your machine to run an Android kernel, you’ll need to have any modules needed by Android built and loaded before you can start the container.

Once you have that, you’ll need to create a new container by hand.
Let’s put it in “/var/lib/lxc/android/”, in there, you need a configuration file similar to this one:

lxc.rootfs = /var/lib/lxc/android/rootfs
lxc.utsname = armhf = none

lxc.devttydir = lxc
lxc.tty = 4
lxc.pts = 1024
lxc.arch = armhf
lxc.cap.drop = mac_admin mac_override
lxc.pivotdir = lxc_putold

lxc.hook.pre-start = /var/lib/lxc/android/

lxc.aa_profile = unconfined

/var/lib/lxc/android/ is where the interesting bits happen. It needs to be an executable shell script, containing something along the lines of:

mount -n -t tmpfs tmpfs $LXC_ROOTFS_PATH

cat /var/lib/lxc/android/initrd.gz | gzip -d | cpio -i

# Create /dev/pts if missing
mkdir -p $LXC_ROOTFS_PATH/dev/pts

Then get the initrd for your device and place it in /var/lib/lxc/android/initrd.gz.

At that point, when starting the LXC container, the Android initrd will be unpacked on a tmpfs (similar to Android’s ramfs) and Android’s init will be started which in turn should mount any partition that Android requires and then start all of the usual services.

Because there are no apparmor, cgroup or even network configuration applied to it, the container will have a lot of rights and will typically completely crash the machine. You unfortunately have to be familiar with the way Android works and not be afraid to modify its init scripts if not even its init process to only start the bits you actually want.

I can’t provide a generic recipe there as it completely depends on what you’re interested on, what version of Android and what device you’re using. But it’s clearly possible to do and you may want to look at Ubuntu Touch to see how we’re doing it by default there.

One last note, Android’s init script isn’t in /sbin/init, so you need to tell LXC where to load it with:

lxc-start -n android -- /init

LXC on Android devices

So now that we’ve seen how to run Android in LXC, let’s talk about running Ubuntu on Android in LXC.

LXC has been ported to bionic (Android’s C library) and while not feature-equivalent with its glibc build, it’s still good enough to be used.

Unfortunately due to the kind of low level access LXC requires and the fact that our primary focus isn’t Android, installation could be easier…You won’t be finding LXC on the Google PlayStore and we won’t provide you with a .apk that you can install.

Instead every time something changes in the upstream git branch, we produce a new tarball which can be downloaded here:

This build is known to work with Android >= 4.2 but will quite likely work on older versions too.

For this to work, you’ll need to grab your device’s kernel configuration and run lxc-checkconfig against it to see whether it’s compatible with LXC or not. Unfortunately it’s very likely that it won’t be… In that case, you’ll need to go hunt for the kernel source for your device, add the missing feature flags, rebuild it and update your device to boot your updated kernel.

As scary as this may sound, it’s usually not that difficult as long as your device is unlocked and you’re already using an alternate ROM like Cyanogen which usually make their kernel git tree easily available.

Once your device has a working kernel, all you need to do is unpack our tarball as root in your device’s / directory, copy an arm container to /data/lxc/containers/<container name>, get into /data/lxc and run “./run-lxc lxc-start -n <container name>”.
A few seconds later you’ll be greeted by a login prompt.

Posted in Canonical voices, LXC, Planet Ubuntu, Ubuntu Touch | Tagged | 24 Comments

System images now the recommended way to deploy and update Ubuntu Touch

After over 3 months of development and experimentation, I’m now glad to announce that the system images are now the recommended way to deploy and update the 4 supported Ubuntu Touch devices, maguro (Galaxy Nexus), mako (Nexus 4), grouper (Nexus 7) and manta (Nexus 10).

Anyone using one of those devices can choose to switch to the new images using: phablet-flash ubuntu-system

Once that’s done, further updates will be pushed over the air and can be applied through the Updates panel in the System Settings.

Ubuntu Touch Upgrader

You should be getting a new update every few days, whenever an image is deemed of sufficient quality for public consumption. Note that the downloader UI doesn’t yet show progress, so if it doesn’t do anything, it doesn’t mean it’s not working.

Those new images are read-only except for a few selected files and for the user profile and data, this is a base requirement for the delta updates to work properly.
However if the work you’re doing requires installation of extra non-click packages, such as developing on your device using the SDK, you have two options:

  1. Stick to the current flipped images which we’ll continue to generate for the foreseeable future.
  2. Use the experimental writable flag by doing touch /userdata/.writable_image and rebooting your device.
    This will make / writable again, however beware that applying image updates on such a system will lead to unknown results, so if you do choose to use this flag, you’ll have to manually update your device using apt-get (and possibly have to unmount/remount some of the bind-mounted files depending on which package needs to be updated).

From now on, the QA testing effort will focus on those new images rather than the standard flipped ones. I’d also highly recommend to all our application developers to at least test their apps with those images and report any bug that they see in #ubuntu-touch (


Posted in Canonical voices, Planet Ubuntu, Ubuntu Touch | Tagged | 6 Comments

Introducing the Ubuntu Touch image based upgrader

Some of you may be aware that I along with Barry Warsaw and Ondrej Kubik have been working on image based upgrades for Ubuntu Touch.
This is going to be the official method to update any Ubuntu Touch devices. When using this system, the system will effectively be read-only with updates being downloaded over the air from a central server and applied in a consistent way across all devices.
Design details may be found at:

After several months of careful design and implementation, we are now ready to get more testers. We are producing daily images for our 4 usual devices, Galaxy Nexus (maguro), Nexus 4 (mako), Nexus 7 (grouper) and Nexus 10 (manta).
At this point, only those devices are supported. We’ll soon be working with the various ports to see how to get them running on the new system.

So what’s working at this point?

  • Daily delta images are generated and published to
  • We have a command line client tool (system-image-cli), an update server and an upgrader sitting in the recovery partition
  • The images usually boot and work

What doesn’t work?

  • Installing apps as the system partition is read-only and we’re waiting for click packages to be fully implemented in our images
  • Data migration. We haven’t implemented any migration script from the current images to the new ones, so switching will wipe everything from your device
  • Possibly quite some more features I haven’t tested yet

So how can I help?

You can help us if:

  • You have one of the 4 supported devices
  • You don’t use that device for your everyday work
  • You don’t need to install any extra apps
  • You don’t care about losing all your existing data
  • You’re usually able to use adb/fastboot to recover from any problems that might happen

If you don’t fit all of the above criteria, please stick to the current flipped images.
If you think you’re able to help us and want to test those new images, then here’s how to switch to them:

  1. Get the latest version of phablet-tools (>= 0.15+13.10.20130720.1-0ubuntu1)
  2. Boot your device
  3. Backup anything you may want to keep as it’ll be wiped clean!!!
  4. Run: phablet-flash --ubuntu-bootstrap
  5. Wait for it to finish downloading and installing
  6. You’re done!
  7. To apply any further update, use: adb shell system-image-cli
    (never use phablet-flash after the initial flash, updates can only be applied through system-image-cli!)

Reverting to standard flipped images:

  • Boot your device
  • Backup anything you may want to keep as it’ll be wiped clean!!!
  • Run: phablet-flash –bootstrap
  • Wait for it to finish downloading and installing
  • You’re back to standard flipped images!

To report bugs, the easiest is to go to:

We also all hangout in #ubuntu-touch on


Posted in Canonical voices, Planet Ubuntu, Ubuntu Touch | Tagged | 11 Comments