Prerequisite: Your Nexus 7 should be running Android 4.1.2 build JZO54K.
- Download the update zip from Google's servers (MD5: 7bee9b220c20979763af563cad56af94)
- If you have a custom recovery, you can just copy it to the device, reboot to recovery, and flash directly as you would any other zip. You're done.
- If you have the stock recovery, carry on.
- Reboot your Nexus 7 and hold the VolDn button while it's booting up. Once you see the fastboot menu and the word Start, press VolUp a few times until you see Recovery and then press the Power button to enter recovery.
- You will see an Android with a red exclamation point. Now press VolUp+Power together, and you should see the menu below.
- Select the 2nd option called apply update from adb.
- Connect the Nexus 7 to your computer with a USB cable.
- Make sure you have adb (if you don't, download the Android SDK or follow this simpler guide to get just the adb/fastboot portion of the SDK without downloading the full thing).
- Keep the file you just downloaded on your computer and open up a command prompt (cmd in Windows, regular shell in Linux and Mac) in the same directory as the zip file.
- Type in:
- adb sideload 094f6629314a.signed-nakasi-JOP40C-from-JZO54K.094f6629.zip
- You should see the progress bar go up to 100%, like so:sending: 'sideload' 100%
- At this point, the device should have started installing the update.
- Reboot - you're done. Enjoy Android 4.2 on your Nexus 7!