Beginning from today, Google has started rolling out the Android 4.1.1 Jelly Bean OTA update for the Galaxy Nexus. However, as of now, the update will only be pushed to the takju variant of the Galaxy Nexus, which is sold directly by Google on the Play Store.
Owners of other variant of the Galaxy Nexus, yakju, will need to wait for possibly a few more days or even weeks to get the official OTA update. If you cannot wait for the OTA update, and would like to install the update manually on your phone, follow the steps below.
Please make sure your phone is running on Android 4.0.4 or Android 4.1, before proceeding further. The steps below are only valid for the GSM variant of the Galaxy Nexus.
Step 1: Download Galaxy Nexus Toolkit from here. Install the toolkit along with all the drivers. Download the stock rooted ROM from here. The de-odexed version will allow for easy theming, while the odexed version will allow for future OTA updates directly from Google. Transfer the desired ROM to your Galaxy Nexus.
Step 2: Start the Toolkit, and connect your phone to the PC with USB Debugging mode enabled. Select the appropriate model of your phone from the Toolkit to proceed further.
Step 3: Select the option to flash any of the custom recovery (TWRP or CWM Touch/Non-Touch).
Step 4: Once the recovery is flashed, reboot the phone into Recovery by switching it off, and then pressing both the Volume buttons simultaneously along with the Power button. Then use the Volume up/down button to navigate and select the ‘Reboot to Recovery’ option by pressing the Power button.
Step 5: Once you boot into recovery, select the ‘wipe data/factory reset’ option, and then the ‘format /system’ option from under ‘mounts & storage’. Then select the ‘install zip from SD card’ option, and navigate to the ROM you trasnferred to your phone back in Step 1 and wait for the flashing process to complete.
Step 6: Once the ROM has been flashed, reboot your phone and if you followed all the steps properly, you should be enjoying Jelly Bean on your Galaxy Nexus!
Credits to bigxie and mskip!