How to root the Samsung Galaxy S2/SII I9100

Posted: December 16, 2011 in Phones

Do following unwarranted (but thoroughly tested steps) at your own risk. Credits to Chainfire from xda-developers.

Useful terms;
Bootloader ~ similar to Grub/LILO in Linux.
Kernel ~ piece of software which interacts with actual hardware on your phone, apps then talk to the kernel to get things (e.g. camera) to work.
ROM ~ think of it as your phone’s whole O/S – usually includes a kernel.
Note: Bootlooader and/or Kernel can be updated independently of the ROM.

“Rooting” just involves installing a new kernel on your phone – exactly the same as being able to replace kernels in Linux distributions. For the exception of the new kernel, BusyBox & Superuser/CWM apps – the rest of your phone’s O/S (settings/contacts/apps etc) remains intact/unchanged.

What you need
1. Odin.
2. Stock kernel tar file (i.e. don’t need the whole stock rom – size should be less than 10Mb) – get details from about phone > kernel version.
3. CF root kernel tar file (size should be less than 10Mb) – get details from about phone > kernel version e.g. I9100XXKI3 > you need a KI3 file.
4. 7-zip to be able to extract tar files both in Linux/Windows.
5. USB to micro-USB cable to connect to phone.
6. Make sure to have installed Samsung KIES so appropriate USB drivers are installed – close KIES before doing steps below.

Procedure
1. Settings > applications > development > tick USB debugging.
2. Power off phone.
3. Press and hold vol down, home and power buttons until advised about custom roms – press vol up to enter download mode.
4. Start Odin, tick PDA option and select CF root kernel tar file (i.e. not the whole rom – just the kernel).
5. Connect USB cable to phone & wait for COM{some number} to appear in Odin.
6. In Odin, press Start to flash.
7. Phone will reboot – it’s now rooted and can be used normally. Continue with steps below if you want to remove yellow triangle during boot.

To remove yellow triangle during boot (i.e. after phone has been rooted)
a. Repeat steps 2 to 7 with 1 difference – select the stock kernel tar file (i.e. not the whole rom – just the kernel).
b. Extract the zimage file from the CF root kernel tar file to main folder of built in sdcard.
c. Start CWM app > select flash kernel option > locate the zimage file on sdcard then flash.
d. All done – phone will of course now be running CF root kernel and not original samsung stock kernel.

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