Update Galaxy Nexus to Android 4.1.2 manually

So the latest version of Jelly Bean, Android 4.1.2, has been released by Google, with the update already rolling out to the Nexus 7 as well as Galaxy Nexus bought from the Play Store in the US, bringing stability and performance improvements. But for those who haven’t gotten the update yet on their Galaxy Nexus? They can of course manually update thanks to the awesome developer community, without waiting for the update to roll out officially.

XDA Senior Member kalo86 has released an Android 4.1.2 ROM for the Galaxy Nexus, which can be flashed via a custom recovery to update to the latest version of Android, and the guide below will walk you through the steps required to do so. The ROM also comes rooted and enables the use of Flash in the browser, though there are no other changes made.

Keep in mind that this procedure requires you to have an unlocked bootloader on the tablet, and unlocking the bootloader will wipe all data on it (though it can be backed up and restored). Make sure you are comfortable with that before going ahead, otherwise you should wait for the official update to arrive.

Let’s take a look at how the Galaxy Nexus can be manually updated to Android 4.1.2.

Compatibility

This ROM and the guide below are compatible only and only with the international GSM Galaxy Nexus, model number i9250. It’s not compatible with Verizon/Sprint variants or any other device. Check your device model in Settings » About phone.

Warning!

The methods and procedures discussed here are considered risky and you should not attempt anything if you don’t know completely what it is. If any damage occurs to your device, we won’t be held liable.

How to Update to Android 4.1.2 on Galaxy Nexus

Part I: Install Android 4.1.2 ROM

This procedure will wipe all your apps, data and settings. Backup your Apps and important data — bookmarks, contacts, SMS, APNs (internet settings), etc. This Android backup guide would help you.
NOTE: Don’t forget to at least note down your network’s APN settings, which are required to make mobile data work. Go into Settings » More » Mobile Networks, click on the APN that is in use, then note down the setting for each field. While APN settings should be automatically restored from network, you can enter them manually if needed to make mobile data work. You can also find your APN details → here.
Unlock the bootloader on your Galaxy Nexus by following the guide → here. This will erase all your data, including the data on the SD card, so back everything up first (see step 1). Skip this step if your bootloader is already unlocked.
[Important!] Install TWRP recovery on your Nexus by following the guide → here. Make sure to flash the GSM version of recovery. You need recovery to be able to install the ROM and can also use ClockworkMod recovery instead of TWRP. Skip this step if you already have TWRP or ClockworkMod recovery installed.
Download the latest version of the ROM from here.
Download the Google Apps package. This will install apps like Play Store, Gmail, etc. which are not present in the ROM by default.
Download Gapps | Filename: Gapps_JZO54K_Picasa.zip
Copy the two files downloaded in step 4 and 5 to the phone (DO NOT extract the files).
Turn off the phone and boot into TWRP/CWM recovery. To do this, press and hold the Volume Up + Volume Down + Power buttons together till the screen turns on. Then, scroll to the Recovery mode option using the volume buttons, then select it using the Power button to restart in recovery.
Now, tap on Backup, then slide the blue circle button at the bottom to the right to start backing up your current ROM, so that you can restore it later if something does not work out with the new ROM. After backup is complete, go back to the main menu by clicking the home button at the bottom left of the screen.
Select Wipe, then select Factory Reset and then confirm the data wipe. This will not wipe your internal SD card’s contents, so do not worry. Then, go back to the main menu by clicking the home button after wipe is complete.
Select Install, then browse and select the ROM file you downloaded in step 4 above. Confirm installation to flash it.
After installation of ROM is complete, repeat step 10, but this time select the Gapps_JZO54K_Picasa.zip file to flash the Google apps package. Confirm again so that gapps are flashed.
After installation of Gapps is complete, select the Reboot system button to reboot the phone and boot up into the ROM. First boot will take up to 5-7 minutes.
NOTE: If you want to go back to your previous ROM, boot into recovery, select Restore, then restore your previous ROM by selecting it from the list.