There are three requirements that need to be fulfilled in order to root your Samsung Galaxy S II successfully. Here are the requirements:
Instructions to Root AT&T Samsung Galaxy S II trough ODIN:
1. First of all, you need to download KIES and install it on your computer. This will install the required Galaxy-s-II drivers on your PC for ODIN to work without issues.
2. When the KIES has been downloaded and installed on your PC, then you need to download ODIN from link provided in Requirements section.
3. After that, unzip ODIN zip folder, you are required to make a new folder named ODIN on your desktop and copy the extracted files to this folder.
4. For the next step, download the System Image zip file from here, extract PDA.tar and copy it to ODIN folder on your desktop.
5. Once done, please launch the application by tapping on Odin3 V1.85.
6. Power off your phone completely and reboot it whole holding volume down button simultaneously with home and power buttons.
7. When you are arrived in the download mode, connect your phone to the computer via USB cable that came with your phone.
8. Once you have connected the phone to the computer, you should now see COM 20 port highlighted with yellow in ODIN application windows. Only leave Auto Reboot checked and uncheck all other options.
9. The next step is clicking on PDA tab and selects the PDA.tar file you downloaded and copied to ODIN folder earlier.
10. Click on Start when you have selected the file.
11. Please wait patiently while ODIN flashes this kernel on your phone.
12. Your phone will reboot automatically once the procedure is complete.
13. Reboot your phone in 3e Recovery and do Wipe / Data factory reset if you are facing a bootloop after flashing the .tar file
2. When the KIES has been downloaded and installed on your PC, then you need to download ODIN from link provided in Requirements section.
3. After that, unzip ODIN zip folder, you are required to make a new folder named ODIN on your desktop and copy the extracted files to this folder.
4. For the next step, download the System Image zip file from here, extract PDA.tar and copy it to ODIN folder on your desktop.
5. Once done, please launch the application by tapping on Odin3 V1.85.
6. Power off your phone completely and reboot it whole holding volume down button simultaneously with home and power buttons.
7. When you are arrived in the download mode, connect your phone to the computer via USB cable that came with your phone.
8. Once you have connected the phone to the computer, you should now see COM 20 port highlighted with yellow in ODIN application windows. Only leave Auto Reboot checked and uncheck all other options.
9. The next step is clicking on PDA tab and selects the PDA.tar file you downloaded and copied to ODIN folder earlier.
10. Click on Start when you have selected the file.
11. Please wait patiently while ODIN flashes this kernel on your phone.
12. Your phone will reboot automatically once the procedure is complete.
13. Reboot your phone in 3e Recovery and do Wipe / Data factory reset if you are facing a bootloop after flashing the .tar file
Note: We do not responsible for any damages when you try this tricks, please read carefully before you do this on your gadgets.