[Nexus S General] agambatra:
Okay First of all download the following files

a)http://android.clients.google.com/packages/ota/google_crespo/VQ8PQk_V.zip (4.0.3 OTA)

b)http://android.clients.google.com/p...a25375426.signed-soju-ota-189904.1ada2537.zip (2.3.6 Official I9020T Build)

c)http://bit.ly/su2361ef (SU flashable)

d)http://xdaforums.com/showthread.php?t=988686 (Grab recovery form this thread)

e)http://developer.android.com/sdk/index.html (Grab the android SDK installer)

f)http://attachments.xda-developers.com/attachment.php?attachmentid=687157&d=1313224429 (Radio file only required for I9020A)

Okay so when done with all that proceed as follows

1) Backup your current apps using Titanium Backup (Optional/Recommended)

2) Backup(Nandroid) your rom using backup option in CWM (Optional/Recommended)

3) Do a full wipe, wipe sdcard, system, data, cache Transfer a,b,c,f to your phone.

4) Flash the 2.3.6 Official I9020T Build you had downloaded using the install zip option in CWM (IMP-DO NOT REBOOT RIGHT NOW)

5) Flash the flashable SU file you had downloaded and then reboot.

6) Once your phone is on, continue to set up your account or skip it as you wish. (Optional)

7) Open up market, download the latest SU app, Voodoo OTARootKeeper, Titanium Backup and any other app you use that requires root.

8) Open the updated SU app, hit menu button and click preferences, go all the way down, click on su binary(tap to check for updates) , and make sure it updates to v3.0.3

9) After that is done, open and allow root permissions to all your root apps. (This is important)

9.5) Run Voodoo OTARootKeeper and click on protect root, make sure all options get checked.

10) Turn off phone, keep volume up and power pressed to boot into fastboot.

11) Select recovery with volume buttons and use power to launch.

12) Once you see a android bot image and an arrow image, keep volume up pressed and press power once, then you'll see some options appear.

13) Select apply update option and find the official 4.0.3 OTA file you had downloaded and flash. Reboot.

14) Once you have booted into ICS, go to Voodoo OTARootKeeper and select resture Root, all options should now be ticked, if not something went wrong.

15) Voila, you have root. Now to get back CWM recovery you can follow this -

i) Place the recovery img file in the android sdk platform-tools folder

ii) Switch to the directory where you unzipped the Android SDK & go to "tools"

iii) Then type "fastboot flash recovery yourfilename.img" & hit enter

iv) That should do it.

v) Optionally you may do it form Rom Manager too, if it works.

16) (ONLY FOR I9020A) Reboot phone, turn it off, boot into fastboot, select recovery, CWM should launch, flash the radio file you had downloaded to get radio working on I9020A (ONLY FOR I9020A)

Root only works for the apps that were installed while on 2.3.6

http://downloads.androidsu.com/superuser/Superuser-3.0.7-efghi-signed.zip , use this root file, flash it in cwm, everything works, permissions etc.

This might work for other variants, tested on I9020A and I9020T, I take no responsibility for anything that might go wrong with your device. I take no credit for any links or procedures provided in this guide, I just tested and compiled.

Thanks and best of luck.