Google has released a beta version of
Android L, the as-yet unnamed next release of the mobile operating system. Anyone can install this on their
Nexus 5 or
Nexus 7, but it’s unwise to do so if it’s your main smartphone or
tablet.
As Google states, “The Android preview system image is not a stable
release, and may contain errors and defects that can result in damage to
your computer systems, devices, and data. The preview
Android system
image is not subject to the same testing as the factory OS and can cause
your phone and installed services and applications to stop working.”
So, you have been warned, but the good news is that you can uninstall
the
Android L preview and revert to factory settings. Just make sure
you have backed up everything that you can’t afford to lose before you
install Android L, since the process will wipe your device.
We’ll explain step by step how to install the preview on a
Nexus 5,
using
Windows 7 or
8, and also how to go back to the original software
that your device shipped with.
How to install Android L
Step 1. Download the minimal 2MB installer from this XDA thread
this XDA thread which includes the Android ADB and fastboot tools.
You need these to install the Android L image, and this is the
quickest and easiest way to install the tools without downloading the
entire Android SDK, which is huge and contains stuff you don’t need to
get Android L.
Follow the instructions (don’t change the installation path when
asked where to install it) and you should end up with a command prompt
window:
Step 2. Download the appropriate file for your device:
Download Nexus 5
Download Nexus 7
You will also need a utility such as
7-zip which
can extract the files from the .tgz archive. In fact, you’ll need to
unzip the files twice, as there’s a .tar file inside the .tgz file.
Extract the files to the same folder as the Minimal ADB and Fastboot,
which is c:\Program Files (x86)\Minimal ADB and Fastboot.
Once extracted you should have a list of files as per the image below.
Step 3. Head to Settings, and scroll down to About
phone at the bottom. Scroll down to Build number and tap it 7 times.
This unhides the developer options, which aren’t displayed in Android
4.2 and later. In the Developer options menu, enable USB debugging.
Step 4. Download the Google USB driver from here
here and extract the zip file somewhere.
Step 5. With your Nexus connected via USB and
powered on, go to the Control Panel and click Devices and Printers. You
should see your device in the list. On our Windows 8 machine, it was
listed as ‘MTP’ under Multimedia devices. Right-click on it, and choose
properties. Click on the Hardware tab, then select the Nexus 5 in the
list, and click Properties. Now update the driver, pointing Windows to
the folder where you extracted the Google USB driver. Once done, it
should report the device as Android Composite ADB interface. Plus, you
should get a prompt on your device’s screen asking “Allow USB
debugging?”. Tick Always allow from this computer and tap OK.
Step 6. Now, Power off your device, and leave it
connected to your computer’s USB port. Now start it using the
appropriate key combination to put it in “fastboot” mode.
For the Nexus 5, that’s by holding down the volume up, volume down
and power buttons simultaneously. You should see a screen like the one
below
Alternatively, you can leave your device on and type adb reboot-bootloader to restart in fastboot mode.
Step 7. If the LOCK STATE says locked (which it should) then type
‘fastboot oem unlock’ at the command prompt, without the quotes, and
press Enter. You’ll see a screen like the one below. To change from no
to yes, use the volume rocker, and to select the option, press the power
button.
This WILL erase your device, so make sure you’ve backed everything up first.
Step 8. With the bootloader unlocked, you can now install the Android L firmware. Simply type
flash-all
and the process will begin. You will see alternating downloading… writing…. erasing… on your device’s screen.
Step 9. When the process finished, you should lock
the bootloader again for security. Start the device in fastboot mode (as
in Step 6), and then type fastboot oem lock
Locking the bootloader won’t wipe any data, but if you unlock it again, it will erase the device of all user data and settings.
How to uninstall Android L and return to factory settings
Reverting to the version of Android you had before installing Android
L is pretty much the same process as you’ve just completed.
Step 10. First, download the correct version of Android KitKat for your device from
Google's images page
You can choose which version of KitKat you want.
Step 11. Then, extract it as in Step 2 above. You’ll
need to delete the Android L files from the c:\Program Files
(x86)\Minimal ADB and Fastboot folder before copying the extracted files
there. These are the files to remove (in case you forgot which were
which).
Step 12. Repeat step 6 to 8, and you'll have a box fresh Nexus 5 (or 7).
