I rooted my Samsung Galaxy S2 today and the actual rooting process went great. Afterwards I made a complete NANDroid backup with ClockworkMod Recovery and I also did a backup of all my apps with Titanium Backup – since I now enjoyed root access Titanium could also backup all the Market links.
However, after I flashed a nightly build of CyanogenMod 7, my device simply refused to start. It got stuck on the boot screen and never loaded Android. Earlier I had used the CWM Manager app to boot into ClockworkMod Recovery, but I couldn’t use it now since Android wouldn’t start. I needed to find out the hardware key combination to boot into recovery mode and restore my NANDroid backup, and luckily I found it.
How to start the Samsung Galaxy S2 recovery mode
To boot the Galaxy S2 into recovery mode, first turn off the device. Then simply press and hold the Volume up button, the Home button and the Power button at the same time. Keep holding the buttons until you have reached the recovery mode.
The procedure for starting the Galaxy S2 in Download Mode is very similar: turn off the phone and hold the Home button, the Volume down button and the Power button at the same time. This will start the Download Mode.
Footnote: Since CyanogenMod obviously didn’t work, I ended up flashing flashed a MIUI ROM instead. It looks really good on the SGS2.