If you're a Galaxy Nexus owner looking to get your hands on all the cool new features of Android 4.2 (check out our complete list here), you're in luck. Google has begun rolling out the newest Jelly Bean update to select GSM Galaxy Nexus owners today – but only those who bought their devices from the Google Play Store (they're called Takju varients).
If you didn't receive the update yet, you can install it manually. As long as you own a Takju varient, are running the latest build (JZO54K) and and you've already rooted your device (or unlocked your bootloader) you can still install the update manually by following the instructions below. It's actually incredibly simple.
1. Download the official update from Google here.
2. Reboot your Galaxy Nexus, and hold the volume up and the volume down buttons simultaneously during the boot up. Once you see the fastboot menu and "Start," press the volume up to navigate to "recovery" and press the power button. You'll now see an Android with a red exclamation point. Press volume up and the power button simultaneously, and you'll be brought to a new menu. From there, navigate to "apply update from adb."
3. Plug your Galaxy Nexus into your computer via your USB cable. Make sure you've already downloaded the Android SDK from Google here. Open up a command prompt (cmd in Windows or regular shell in Linux and Mac) in the same directory as the JOP40C zip file you've downloaded.
4. Type in the following:
adb sideload e587de13bf8a.signed-takju-JOP40C-from-JZO54K.e587de13.zip
5. A progress bar should open, which will eventually hit 100%. At this point, your phone should begin installing the update.
6. Reboot your phone and enjoy Android 4.2.
Source: Android Police