So last week, I decided to flash a custom ROM to my 2 year old Desire HD. I used the all in one, one-step, "rooting" tool called AAHK (It doesn't just root the phone, it does a whole lot like S-OFF, Goldcard, etc).

My DHD is now running Jellytime R30. Everything is good.

Now, I would like to try other ROMS. I did a backup of my current system via Clockworkmod in Recovery.

Question: Is this a full "image" snapshot? I mean, will I be able to restore the entire system including the ROM when I restore this backup? Or do I have to flash the ROM in the snapshot before I restore the backup?

PS: I'm new to this custom ROM thing but I've done my fair amount of research. :)

2 Answers 2


CWM backups are full system backups, so they restore it to exactly how it was when you took a backup. Everything including apps, settings, preferences, even call log is saved.

You don't have to flash the ROM before restoring a backup. The backup files contain a boot.img and system.img that have the ROM, kernel etc in it.

When moving to another ROM, you might also want to take a backup of all your apps and app data with Titanium backup, this is helpful to restore them on the new ROM.

If you flashed a new ROM without using Titanium Backup, don't panic, App Extractor can extract apps and data from a CWM backup. https://play.google.com/store/apps/details?id=com.handyandy.appextractor

My usual flash routine is: backup with Titanium, sync all data on wifi, backup sms, reboot to recovery, do CWM backup and then wipe, flash new ROM, reboot and restore apps, and sync.

Hope it helps!

  • Hmm, why do I need to use Titanium to backup my apps? I thought Clockworkmod backups are "full system backups"?
    – Ian
    Commented Dec 26, 2012 at 12:58
  • Also, what do you mean by "sync all data on wifi"?
    – Ian
    Commented Dec 26, 2012 at 12:58
  • Full system backups, yes but without app extractor you can't restore apps to a new ROM. That's where Titanium comes in. Sync data(contacts, settings and wide pwds etc) on wifi so you can have them back on new ROM simply by syncing again. Wifi so you don't exhaust your 3g limits!
    – Sumesh
    Commented Dec 26, 2012 at 13:30

What ClockworkMod does is a so called Nandroid Backup. Basically, this contains an image for each of the file systems of the device (i.e. one image per file system) -- and thus it is a full backup/"image snapshot". The format of the snapshot might differ and depend on the device and ClockworkMod version being used; for my Motorola Milestone 2 most of the file systems seem to be captured as YAFFS2 image, i.e. the image uses the same file system used on the device. So it is comparable with using dd on Unix/Linux (see Wikipedia), at least in my case.

Newer versions of ClockworkMod Recovery (6.0 and up) also do "incremental updates" to save space on the backup medium and allow for faster backup (see e.g. this TechieBuzz.COM article). For this, you might also want to check our question How can I tell CWM to perform a full backup instead of an incremental backup?

More details you can also find by following the tag.

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