OTA (over-the-air) updating in rooted Nexus land has never been the most elegant process. But, prior to Android 5.0 Lollipop, at least it worked as expected, with the main irk being that you’d need to re-root your device afterwards.
While trying to update to Android 5.0.1 on my rooted Nexus 5 via OTA today, I discovered that things are now even less clear-cut and that the update itself will now fail during the recovery phase. Thankfully, there’s a (relatively) pain-free way of getting around this, providing your comfortable with fastboot at the command line.
This guide presumes you’re using either Linux or Mac, with the appropriate Android tools (adb and fastboot) installed, although the Windows method should be much the same. For the purposes of this example, I’ll assume this is the Android 5.0.1 update for Nexus 5 (hammerhead-lrx22c), but the instructions should be similar for future releases.
Note: This will not wipe your device. However, it is always a good idea to back up, as things can always go wrong.
First, download the appropriate Android factory image from the Google Developers site. Uncompress the archive, as well as the archive contained within it, as below:
$> tar -zxf hammerhead-lrx22c-factory-0f9eda1b.tgz
$> cd hammerhead-lrx22c
$> unzip image-hammerhead-lrx22c.zip
Next, make sure your device is in fastboot mode (hold VolUp, VolDown and Power button from a powered-off device). Verify your device can be picked up by running fastboot devices, then run the following commands:
$> fastboot flash radio radio-hammerhead-m8974a-126.96.36.199.22.img
$> fastboot reboot-bootloader
$> fastboot flash recovery recovery.img
$> fastboot flash boot boot.img
$> fastboot flash system system.img
If all goes well, your device will be flashed with the latest version of Android.
Bonus – re-root your device: grab the appropriate version of CF-Auto-Root for your device, extract it and run the correct root script contained within. Your device will need to be in fastboot mode for this to work.
Credit to /u/laxor09 on Reddit for much of this information.