Finally, I have decided it’s time to root my Samsung Galaxy S2 Android device.

Some of my reasons for rooting:

1. Installing custom ROMs / mods and kernels requires root access.
2. Performing a good backup of the device (apps & data, system & user) requires root access.
3. Getting rid of unwanted system apps requires root access.
4. My M.Sc. research will include writing a kernel module for the Android kernel, so better start getting comfortable with low-level now, right?

This post is a detailed (photo-documented) walkthrough of the rooting process. The rooting is done using Odin3 and CF-Root.

Up until last year, my “mobile presence” included no more than a last-decade Nokia handset, and a Work-Issued zero-functioning Motorola i876.

During August 2011 the Nokia battery passed away (at old age, it should be noted), so I treated myself with my first Smartphone – an off-the-shelf Samsung Galaxy S II (GT-i9100) (get your own from eBay or Amazon), running Android 2.2 (I think) with stock Samsung TouchWiz.

In fear of voiding my warranty, I decided to take advantage of the first year with an Android device to explore to basic user aspects, and just be a Simple User, playing around with apps, launchers, dialers, etc.

Once the warranty reached its natural demise, I started looking at what fun stuff I can do with my device, and realized most stuff require a rooted device. Hence my first task.

The rest of this post documents the rooting procedure I performed, for self-future reference, and maybe also as a useful reference for others (who knows).

Naturally, the first thing I did was to Google for How-To guides, tutorials, etc.. As one might assume, I got tons of results. The most helpful guide I ran across was at AndroidNZ – a post titled How to Root your Samsung Galaxy S II (what a coincidence..!), which is, give or take, what I followed in order to root my own device. So here goes:

Setup & Prerequisites

1. My PC is a Windows machine, so I pre-installed Samsung Kies, in order to have all required drivers present (looking for the “SAMSUNG Android ADB Interface” in Device Manager, as demonstrated by the screenshot)
   

   

   Locating the SAMSUNG drivers in the Windows Device Manager

   
   
2. Odin3 is used to download stuff from the PC over the ADB interface to the device. I downloaded version 3.04 from AndroidFirmwares.net, and it looked like this:
   

   

   Main screen of Odin3

   
   
3. Found out the current kernel version info, needed for choosing the right CF-root kernel later.
   1. On the phone, go to Settings -> About phone -> Kernel version, which looks like this on my stock Samsung ICS:
      

      

      Finding out the kernel version of stock Samsung ICS Android

      
      
   2. Note the Kernel version string (in my case – 3.0.15-I9100UHLPE-CL200654), and write down the 3 letters that follows I9100XX (LPE in my case).
4. Download the CF-Root kernel for the correct version from the XDA-Developers thread (simply run a search on that page for the 3-letter-version from the previous step) – I downloaded CF-Root-SGS2_XW_OXX_LPE-v5.5-CWM5.zip (which means CF-Root v5.5, with integrated ClockWorkMod v5.5). Extract the .tar file from the .zip file.

5. Have the device fully-charged, and a micro-USB cable at hand.

Let the rooting commence

1. Extract Odin3 and run it (no installation needed) – see screenshot above.
2. In Odin3, under Files [Download], select the CF-Root-SGS2_XW_OXX_LPE-v5.5-CWM5.tar file for the PDA option.
3. Make sure the Re-Partition option is NOT checked.
4. Odin3 looks like this when it’s ready:
   

   

   Odin3 screen after configured and ready for flashing CF-Root

   
   
5. Power down the phone, and put it into Download mode (simultaneously press and hold the Volume-down and Home buttons, and while holding the buttons press the power button until the phone powers up, looking like this):
   

   

   Entering download mode on the Samsung Galaxy S2

   
   
6. Confirm entering Download mode by pressing Volume-up:
   

   

   Samsung Galaxy S2 device in download mode

   
   
7. Now connect the phone to the PC via USB, and wait for Odin3 to recognize it (in my example – the phone was recognized on COM4 with ID 0):
   

   

   Odin3 screen with phone connected and recognized, ready for download

   
   
8. Press Start in Odin3 to download the kernel to the phone:
   

   

   Odin3 screen during the process of downloading (flashing) the image to the device

   
   
9. Should finish pretty quickly:
   

   

   Odin3 screen after kernel flashing is completed

   
   
10. That’s it. The phone is rooted. This is evident both during power up, as a yellow warning triangle:
    

    

    Samsung Galaxy S2 rooted yellow triangle during boot

    
    
    and a little less pronounced on the About phone screen, that shows a somewhat different kernel version string:
    

    

    Samsung Galaxy S2 about screen after rooting

    
    

Conclusion

That’s it. Hope the information comes in handy.