How to change the Ubuntu installation to read-write mode on a mobile device

You can use the experimental writable flag, as explained in the system images announcement.

Note that once you've changed a RO installation to RW there is no going back. The only way to go back to RO mode is to reflash your device with ubuntu-device-flash.

OTA updates are still delivered to your device, but each one is at your own risk –you may have made changes that mean the OTA has bad side effects. If your device becomes unbootable, use ubuntu-device-flash to recover.

All that said, here's how to switch your device's Ubuntu installation to RW mode:

  1. Ensure your device is connected to the host computer via USB, Developer Mode is enabled and the screen is unlocked.
  2. Start a terminal on your host computer with (Ctrl+Alt+t) and run the following command:

    phablet-config writable-image
    

After reboot your device will be in RW mode and you should be able to write to the file system to e.g. install packages for testing.