Do you love to try out different ROMs on your Nexus 7? There are lots of custom ROMs out there and while it is fun to try them out, it can get a bit frustrating flashing backwards and forwards between new ROMs and your daily driver.
There is an easier way! MultiROM allows you to have multiple ROMs installed on your device and gives you the ability to switch between them at will. ROMs can be Android, Ubuntu Touch or plain vanilla Linux and can run from either your internal device storage or an attached USB drive. The data partition is fully segregated for each ROM, so you don’t need to worry about that new experimental ROM destroying your precious data (although, of course, you should keep backups as MultiROM is an inherently ‘hacky’ solution!).
In order to support MultiROM, you just need to use a kernel built with MultiROM support, of which there are many. You can install as many ROMs as you like, limited only by your device storage space.
This tutorial will take you through preparing your Nexus 7 for MultiROM, installing the MultiROM tools and installing additional ROMs alongside your current choice. We’ll also show you how to revert your device back to the factory state should you wish to remove MultiROM.
Download the fastboot tools
Fastboot is available for Windows, Mac and Linux and is included in the Android SDK at http://developer.android.com/sdk. Fastboot is required in order to unlock the bootloader on your device, an essential for installing MultiROM and custom ROMs. Note that unlocking will wipe your device – backup essential data first!
Put your device in fastboot mode
To put your device in fastboot mode, turn it off and then turn it back on with the volume down key pressed. You’ll see a picture of an Android with his belly door open! In the onscreen text the top line should say ‘FASTBOOT MODE’ and the bottom line should say ‘LOCK STATE – locked’.
Unlock your bootloader
Connect the device to your computer and open a command / terminal window. Change directory to where the fastboot utility is located and type ‘fastboot oem unlock’. Select ‘Yes’ on the device screen using the volume keys to move and power button to confirm.
Download the MultiROM recovery
One of the key components of MultiROM is a customised recovery – this performs the installation and management of ROMs on your device. The .img file, which is a modified version of TWRP, can be downloaded from http://forum.xda-developers.com/showthread.php?t=2093797
Install the MultiROM recovery
To flash the MultiROM recovery, your device needs to be in fastboot mode again, so turn the device off then power on with the volume down key pressed. We’re going to use fastboot again, but this time using the command ‘fastboot flash recovery filename.img’ (using the filename of the .img you just downloaded).
Download MultiROM and load recovery
Now that you have installed the custom recovery, you need to download the MultiROM boot menu itself. This is an update zip file which can also be found at http://forum.xda-developers.com/showthread.php?t=2093797. After copying the file to the internal SD card, use fastboot mode again to boot recovery (using the volume / power buttons to select).
The final step is to install the MultiROM boot menu. The recovery image is fully touchscreen enabled and very easy to use. Press the ‘Install’ button, scroll down the list to select the zip file you copied across then swipe to confirm the flash. Press the reboot button when it’s complete and you’re all done! You’ll see the new MultiROM boot screen with your previously installed ROM available.
Add additional Android ROMs
Installing additional ROMs is carried out via recovery, but instead of just installing the zip as normal, you need to select the ‘Advanced’ menu in recovery followed by ‘MultiROM’. There you’ll find the ‘Add Rom’ option, which will then prompt you to select the ROM zip file. You can also delete /rename ROMs in the same screen.
Add a Linux / Ubuntu Touch ROM
As well as Android, Linux and Ubuntu Touch ROMs are also supported by MultiROM. Both can be found at http://forum.xda-developers.com/showthread.php?t=2093797 and will happily live alongside your Android installations. If you’re feeling really adventurous, there’s even a WebOS Alpha release available to install. Retro!
Reverting back to stock
The easiest way to remove MultiROM way is to revert back to the stock image from Google which can be found at https://developers.google.com/android/nexus/images. Download the image, extract and run the flash-all script while in bootloader mode and you’ll be back to factory default.