Not to be outshone by the big-boys, the GNU-Linux distributor Canonical has developed its very own touch-optimised build of its Ubuntu desktop operating system suitable for ARM devices.
Before you go any further this is the Ubuntu Touch Developer Preview. We think even calling it a Preview is a stretch, as there's little you can do with it other than build your own apps. Put another way, if you're not a developer or enthusiast this isn't for you.
We also want to emphasis this process REQUIRES that you entirely wipe your Nexus device. There's no getting around that, so if there's anything precious on your Nexus, again this isn't for you. We'd also say the OS is currently not in any day-to-day usable state, it looks lovely but lacks all the basic applications and tools. So it's likely you'll give it a whirl, have a bit of fun and go back to Android.
If you've installed a custom ROM on a tablet or phone before then the process is effectively identical to that, but slightly more official. The main steps that we'll take you through are switching Android to its developer mode, unlocking the bootloader, rooting the device and finally flashing the new Ubuntu Touch image. As we're nice, we'll also explain how you can use the same tools to restore your Nexus 7 back.
Disclaimer: Future Publishing Limited provides the information for this project in good faith and makes no representations as to its completeness or accuracy. Individuals carrying out the instructions in this project do so at their own risk.
Let's note some details about your Nexus down. Select Settings > About and note the version of Android it's running and the Build Number at the bottom. We're also going to be heavily using Google Nexus 7 Toolkit created by the geniuses over at XDA Developers, download and install it.
Before starting you might want to have on hand, the correct Google Android default image for your device. Note the Build Number and download the right replacement from Google.
Back up your Nexus now, copying off any photos, documents, files and so on that are not saved elsewhere, as these will all be destroyed as part of this process. You could also do this using a back up app.
1. Get Unlocked
You need to switch your Nexus 7 into Fastboot Mode, this is its bootloader from which you can do recovery and flash procedures. Power down the device, once off press and hold the power button and the volume up and down buttons. After a second or two the Fastboot menu appears don't select anything, plug the device into your PC using a USB cable. If you've never done this type of thing, you may have to wait for the debugging drivers to install.
Run Nexus Toolkit, only people that have donated can check for updates, but don't worry when prompted just select the nearest version of Android, as long as it's within a point-build it'll be fine. Select three to Unlock/Lock from the menu, it'll offer a lot of advice but type "yes" and accept the warning that appears on the Nexus screen. Be aware this will WIPE ALL OF YOUR DATA.
It's best to have Android in its developer mode with USB debugging mode enabled. This enables you to access the device from your PC, with the drivers installed from the Nexus Toolkit. With Android running select Settings > About and tap the bottom Build number seven times to enables Developer mode and access to its options. Go back to the Settings and select Developer options > USB debugging. With Android 4.2.2 a key needs to be accepted on the tablet.
3. Root it
Ubuntu can only be flashed to a rooted device, again Nexus Toolkit can do this for us. The Nexus needs to be in Fastboot mode and connected to the PC. Select option four Root/Unroot and within here the basic Rooting option one. There's an option as to the Super User tool to use, we'd suggest option two for SuperSU, but it's not really important.
USB Debugging needs to be on, but if you haven't booted into Android and set USB Debugging, Nexus Toolkit can do this for you. Read its directions and type "no" at the prompt about USB Debugging. This requires an extra automatic reboot but takes care of everything. It's so helpful!
Ubuntu Touch does provide a bootloader but you don't need it. In fact we going to say in the Nexus ToolKit use option six to install the CWM Touch custom Flash Recovery, with the Nexus is in Fastboot mode. ClockWorkMod is an advanced recovery bootloader, accessed via the Recovery Mode in the Fastboot menu. Let the Nexus ToolKit install this, we'll use this later to flash the Ubuntu files.
5. Files to flash
At this point your Nexus is ready to be brain wiped with Ubuntu. All the Ubuntu Touch Preview stable-build files for the various Nexus models can be found here. Th latest nightly builds can be found here.
For the Google Nexus 7 the ones to download are:
We're only going to use the two ZIP files, the IMG is for a replacement bootloader that's not actually required. You need to copy these to a location on your Nexus 7, the easiest option is boot into Android, connect it, then copy these across using the standard USB connection to the default location.
6. Flash and Go
With the files on the Nexus, reboot into the Fastboot, select Recovery mode to start CWM Touch. Select Install zip from sdcard > Choose zip from sdcard. Where it is depends on your version of Android, it's likely under 0/ and then scroll down to see the two zip files. Install the smaller "armel+grouper" zip first and then the larger "phablet-armhf" zip. Reboot and enjoy what there is of Ubuntu Touch to enjoy.
These aren't real apps.
7. Android please!
Putting Android back using Nexus Toolkit is a breeze. Using option nine it'll download the latest factory build from Google and install it automatically. If you've already downloaded the ROM just copy this into the Google_Factory folder within the Nexus Toolkit folder, found in the root of your boot drive and let it do the rest. As mere cats are taken to say, simples.