You’ll need to grab the OTA update ZIP package for your required device. Google that, should be easy to locate. It’s also noteworthy that, thanks to the developer community at XDA, you can also grab a pre-rooted 4.2.1 package, if you want to achieve that.
Also, you must be on a computer that has the latest version of ADB installed and configured.
Procedure
There are two different approaches to how you can install the update, depending on whether you’re running the stock recovery, or a custom one.
With Custom Recovery
Step 1: Move the update package for your device to the root of your internal memory.
Step 2: Reboot the device into recovery.
Step 3: Choose Install ZIP from SD Card, followed by Choose ZIP from SD Card.
Step 4: Point to the update package, and flash it.
Step 5: Reboot the device, and as soon as that is done, you have the latest 4.2.1 update on your Google Nexus 4, Nexus 7 or Nexus 10.
With Stock Recovery
On a stock recovery image, it’s not as simple, albeit not really difficult.
Step 1: Reboot your device while holding the Volume Up and Volume Down buttons pressed together, which will bring you to fastboot menu.
Step 2: Select Recovery from the said menu, which will bring an Android doodle with a red exclamation sign.
Step 3: Hit Volume Up and Power buttons together, and a new menu will pop up, where you need to now choose apply update from ADB.
Step 4: With your device connected to the PC through USB cable, launch a command prompt window, point to the folder where you have the update package located, and run the following command:
adb sideload ZIP_FILE_NAME.zipwhere you need to replace the ZIP_FILE_NAME part with the actual name of the ZIP package.
Step 5: Let the update complete and reboot, and that’s it, you have the latest 4.2.1 update on your device. Enjoy!
