For those of you who want to unroot to official ICS on your AT&T Galaxy S2 SGH-i777, here’s how to do that using ODIN. This will get everything back to stock including your recovery but you can always re-root it easily.
If you don’t want to lose ClockworkMod Recovery and Root, you can also flash the CWM-zippable official ICS update in ClockworkMod Recovery.
Step 1. Plug in a micro-USB cable from your computer to your AT&T Galaxy S2 SGH-i777. Then hold down Volume Up, Volume Down, and Power buttons together for about 10 seconds.
Step 2. When you see the warning sign hit Volume Up button to enter ODIN Download mode.
Step 3. Download ODIN and AT&T official tar file:
Unzip the ODIN zip file and also the ICS tar file. Run the ODIN program.
Step 4. Choose “PDA” and select the file I777UCLE5_I777ATTLE5_I777UCLE5_HOME.tar.md5 and hit “Start”. DO NOT TOUCH ANYTHING ELSE!
Step 5. In about 5 minutes, your phone should reboot into bootloader once, then into system.
Step 6. You should now find yourself with a fully unrooted AT&T Galaxy S2 SGH-i777 with I777UCLE5 version. Congrats, you are now on official AT&T ICS completely unrooted.
Step 7. If you get any errors like force closes or bootloops, you can do a factory reset. Hold down Volume Up, Volume Down, and Power buttons together for 10 seconds.
Step 8. Choose “Wipe data/factory reset”.
Step 9. Choose “Yes — delete all user data”.
Step 10. Reboot and you should be all good to go!