Upgrading and wiping a Google Nexus 7 or any Android device can be a scary process, especially if you've never done it before. If you're selling a device, passing it on, or picking up an old Android tablet, you want to be sure it's as good as new.
At the very least you'll want to run a factory reset, but better than a reset is ensuring that you're running the latest build of Android too.
The benefit of owning a Nexus model is that it gets the latest Android release first. Beyond just an Android update, options to unlock your Google Nexus provide greater flexibility and features not supported by standard devices.
Flashing the original Google Android build completely resets your Nexus back to its factory state. Beyond selling, for your own use Android isn't immune to being overloaded and occasionally you might just want to wipe the lot and start from scratch.
A complete clear
Before we go any further, some of you might be thinking, "What about a factory reset?" It's a good thought - and if you do want to reset your tablet, that should be your first step.
Select Settings > Backup & reset > Factory data reset. Boom! You've reset your device to the factory default. If, for any one of many reasons, you want to flash an official Google Nexus firmware, the company makes a full range of different versions freely available for you to download. This enables you to reset the device to its shop-bought condition or refresh it to the latest build. The question is how?
The official route is to use a command called 'fastboot' that's part of the Android SDK. We're going to recommend you download and install Google Nexus 7 Toolkit created by the clever ladies and gents over at XDA Developers.
There are a few things you need to know how to do before continuing. The first is how to discover exactly which build of Google Nexus you have.
Select Settings > About and make a note of the Build number. The original WiFi release was JZ054K, the latest 4.2.2 is JDQ39 and the 3G version is also JDQ39, but it uses a separate firmware release to support the 3G radio.
While in the About section, you can also put your Google Nexus into Developer mode. This enables external software to do all sorts of unspeakable things to your Nexus.
From Android 4.2 onward, under the About section, you need to tap the Build number seven times. This opens up the hidden Developer options settings menu.
Go back to Settings and select this. Make sure Developer options are switched on at the top and then activate the USB debugging mode.
Finally you need to switch your Nexus 7 into Fastboot mode. This is its bootloader from which you can do recovery and flash procedures.
Power down your device, and once off, press and hold the power button and the volume up and down buttons. After a second or two the Fastboot menu appears.
Don't select anything, but plug the device into your PC using a USB cable. If you've never done this type of thing before, you may have to wait for the debugging drivers to install. If there's a driver install problem, use the Nexus Toolkit to install this using option one.
By default, Android devices are set in a locked state. This protects their bootloader and stops malicious programs managing to do anything, well, malicious. To perform a flash it needs to be unlocked.
Run the Nexus Toolkit and it'll ask you what version of Android you have. Only people who have donated can check for updates - don't worry if you're not offered exactly the right release, just select the nearest version. As long as it's within a point-build it'll be fine.
Select option three to Unlock/Lock from the menu. At this point it'll offer a lot of advice, but as a rule, type "yes", as we have the Nexus in Fastboot mode and plugged into the PC. Accept the warning that appears on the Nexus screen only if you are happy to WIPE ALL of your data.
At this point you're ready to flash your Google Nexus 7. You'll need to nab the right firmware from Google, but, as you now know the correct build, that's easy to do.
Once downloaded, place the TGZ file into the "put_google_factory_image_here" folder that the Nexus 7 Toolkit created in the root of your boot drive - usually the C drive. We recommend copying the file, as it'll be removed after the process is complete and you may want to hold on to a spare copy.
Start the Nexus 7 Toolkit, boot the Nexus 7 into Fastboot mode and plug it into your PC. In the Nexus 7 Toolkit, select option nine to flash the Nexus 7, then select option two.
After that, type Yes as, you're in Fastboot mode. Wait for the device to reboot - don't touch anything. You'll be asked if the User Data should be formatted for a complete wipe - choose Yes. If you're planning on selling the device at this point, it's wise to relock the bootloader with option three.
Root it and boot it
Unlocking a device early on is a good idea. If you're planning on rooting, adding a custom bootloader and generally taking Android beyond the Google basics, you'll need to do this. It wipes the device, so it's best done right at the start.
Additionally the Nexus 7 Toolkit enables you to flash a custom Fastboot recovery mode, such as CWM Clockworkmod Recovery using its option six. Accessed via the Fastboot Recovery option - use the volume button to display it and the power button to select - these custom recovery tools offer far greater flexibility and backup options than the basic Android Recovery.