For those of you who rooted your T-Mobile Galaxy S2 SGH-T989, I HIGHLY advise you to make a backup of your rooted stock ROM just in case something goes wrong.
Here’s how to backup ROM on your T-Mobile Galaxy S2:
Make sure you have an external microSD card inserted on your T-Mobile Galaxy S2 before beginning as backups are only saved to your external microSD.
Step 1. Download ROM Manager off the Market and install.
Step 2. Open up ROM Manager and choose “Flash ClockworkMod Recovery”. This will install the latest version.
Step 3. Choose “Reboot into Recovery” and your T-Mobile Galaxy S2 will reboot into ClockworkMod Recovery.
Step 4. Choose “backup and restore”.
Step 5. Choose “backup” to start the backup process.
Step 6. Once backup is complete you can choose “reboot system now” to reboot.
Step 7. Optionally, you can rename your backup folders to something more memorable using ES File Explorer app (free on the Market). Install the app and open.
Step 8. Hit Menu then Settings. Check Root Explorer and Mount File System ON.
Step 9. Browse to your backup folders in external micro SD card, it’s in /sdcard/external_sd/clockworkmod/backup. You can also copy the contents of this folder to your hard disk so it doesn’t take up space and copy it back when you need it to the same directory.
Step 10. Do a long-press on the backup folder you just made a backup of and choose “Rename”.
Step 11. Rename it to something more memorable, I added the word “stock” after the timestamp to note that this is my stock rooted ROM.
Step 12. You can use this backup/restore feature on the ClockworkMod Recovery to backup several different ROMs and change them on the fly by using the restoration function.