GS2 Rooting and Flashing Rom

Things to do:

1. For the time in 5/10/2011, the latest official rom is ZSKG2 which is for HK phone model. So I upgrade my phone from KF4 to KG2 with the Samsung Kies software. (Note: when you connect your phone with Kies, make sure the debug mode is turned off....)
2. Go to XDA download Odin3-1.85 and the CF-Root kernel which is a kernel that has already been rooted. For my phone, I need this: CF-Root-SGS2_ZS_OZS_KG2-v4.1-CWM4
   http://forum.xda-developers.com/showthread.php?t=1103399
3. The next step is pretty simple. Boot to the download mode, and start Odin to flash the rooted kernel. It just takes you no more than 5 minutes. Done!
   http://www.hkepc.com/forum/viewthread.php?tid=1627473&extra=&page=1
4. Reboot. You will see an exclamation mark in the boot screen. It is normal as the system detected an insecure kernel.
5. From your app drawer, you will find two new icons. 1) Superuser; 2) CWM (ClockWorkMod)
6. Now your phone is rooted and you can use all kinds of root-required apps from Market, such as Titanium Backup. You can also flash other roms!
7. Before you do it, make a backup of your original rom for safe. You can do that in CWM.
8. Also, guys in XDA recommend to do a backup for the efs folder of your phone. The phone contains some phone-unique-and- specific information. Do it with the shell command listed here:
   http://forum.xda-developers.com/showthread.php?t=1068193
9.