For those of you who want to root your Galaxy S2 GT-i9100 on Jelly Bean Android 4.1.1 or Android 4.1.2, here’s how to do it easily using a custom kernel.
This rooting process is pretty safe to do, does not erase anything on your phone, it just installs a custom kernel (which comes with a custom recovery) and we root the phone using SU binary and Superuser app. That’s it! Step 1. Turn your Galaxy S2 GT-i9100 off. Then hold down Volume Down, Center Home, and Power buttons together for about 3 seconds until you see the warning screen.