How To Root Galaxy Nexus On Android 4.0.2 ICS

You Need to first install ClockworkMod recovery, go here to find out how.
Step 1: Download the required kernel for your Galaxy Nexus:

• CF-Root (GSM) [Build: ICL53F]
• CF-Root (LTE) [Build: ICL53F]

You can check which version you should download by going to Settings > About phone and observing the build number. Extract the .zip file. Step 2: Ensure that your device is not connected to your computer.
Step 3: Download ODIN v1.85 [XDA Thread]. Launch it.
Step 4: Click on PDA and select CF-Root-xxx-vX.X.tar which you will find in the folder you extracted in Step 1.
Step 5: Switch off your Galaxy Nexus. Once it is completely shut down, press and hold Volume Down + Power buttons to boot into download mode.
Step 6: Once in download mode, connect your Galaxy Nexus with your computer.
Step 7: Ensure that you have not checked the Re-Partition option.
Step 8: Click on START and wait for your device to reboot.