Backing up an Android device is a broad term, that entails various levels of backup that cover multiple aspects of the data on your Android device, using different tools.

In this post I cover the concept of NANDROID, which refers to a low-level backup of the device, including practically everything that resides within the partitions on the NAND flash of the device – kernel, ROM, apps & data, system data, etc.

NANDROID backup is a snapshot of your device at a specific point in time. As such, it allows restoring the device to the exact state it was when the snapshot was taken. This is a pretty good safety net when experimenting with the device.

NANDROID backup does not include data on the SD card!

A useful reference I used and followed is “How to backup your Rooted ‘Droid – NANDROID & Titanium Backup“, on the AndroidNZ blog.

Performing a NANDROID backup requires a rooted device, with a custom recovery that has a NANDROID backup option, like ClockWorkMod Recovery.

As I rooted my Galaxy S2 by flashing a CF-Root kernel, I already have ClockworkMod Recovery installed (v5.5.0.4), which simply offers a “Backup” function. What follows is a description of the steps to perform a NANDROID backup using CWM on Samsung Galaxy S2 i9100:

1. Launch the ROM Manager app
2. Select Backup Current ROM
3. Enter a name, e.g. 2012-09-14-PostRoot
4. After confirming, the device will reboot into CWM Recovery and perform the backup, which looks something like this:
   

   

   Running the NANDroid backup in CWM-based recovery on Samsung Galaxy S2

   
   
5. Once the backup completes, the device will reboot, and the backup data can be found on the sdcard, under /clockworkmod/backup/2012-09-14-PostRoot.
6. In order to really call this a “backup”, I copied the backup directory from the sdcard to my Dropbox folder (@Dropbox/Backup/SGS2/ClockWorkMod/2012-09-14-PostRoot), so I don’t end up with a single copy (single point of failure) stored on the device that I’m about to tamper with…

That’s it for the NANDROID backup (pretty simple, eh?).

I don’t know of a way to automate it, but I don’t think it’s needed here, since it’s more of a “restore-point” kind of backup which is a good idea when making “major operations” (like flashing ROMs and kernels).