Ubuntu Touch Devices

Introduction

For now we're assuming that Ubuntu Touch runs in a container on top of an Android system. However the design is sufficiently flexible to easily adapt if we decide to drop that split or flip the two (make android the container).

Paritioning and file system

We're currently assuming we can't easily repartition the device and so make use of the standard partitions. The Android system lives on the system partition, usually accessible as android:/system.

Temporary storage can be found at android:/cache and will be used to store the update images.

The Ubuntu system is installed in android:/data/ubuntu/, that directory will then contain at least two files:

• system.img - ext4 file containing the system. This partition will become ubuntu:/ (/ of the container) and mounted read-only.
• data.img - ext4 file contaiing the userdata. This partition will be mounted to ubuntu:/data (for example) and contain all user data and configuration.

The current version of the system is stored in ubuntu:/etc/ubuntu-build

Recovery partition

The recovery partition will include a custom kernel+initrd used for our updates and factory reset. This will support:

• Menu based options allowing the user to flash from eMMC and do factory reset.
• Automated update mode that can be triggered by the update client and which will automatically apply any pending update.