March 30, 2012
You need to upgrade your Nexus S to 2.3.6 in order to upgrade ICS ( 4.x ). This steps are for the phone model I9020 and I9023 from the Android version 2.3.x to 2.3.6. This is an official ROM which you can download it from Google site itself.
If you follow this guide carefully, you should not run into any problems. However, there is always a very small chance that you may brick / destroy your phone. We are not responsible for any damage that may be caused throughout this guide.
Step 1 : Before You Start
I prefer to take a backup before I perform any update, hence I recommend you to take a backup.
Download the Android 2.3.6 update & rename it to update236.zip
Make sure that your phone is fully charged throughout this upgrade.
Step 2 : Connect your Nexus S to your computer via USB and copy update236.zip to the root of your SD card (Do not drop it into a folder or this won’t work!).
Step 3 : Power down your Nexus S Phone.
Step 4 : Power your device on, while holding the Volume Up button, followed by Power button.
Step 5 : Use the volume buttons to navigate to RECOVERY mode and press the power button.
Step 6 : When you see the exclamation mark on the screen, DON’T PANIC! Hold the Power button followed by Volume up button.
Step 7 : Select the option to Update from SD card select the update236.zip package you downloaded earlier and press the power button to confirm.
Step 8 : The update will now install automatically. When it’s down your Nexus S will boot up into Android 2.3.6.
Now your phone is ready to upgrade to ICS. Enjoy using Android