I have an Nexus 10 device that recently offered the 5.0.1 OTA update. After the update the device would boot loop to a screen with a dead robot with an exclamation point and the message 'no command' underneath. How to recover?
After trying factory reset and wiping the cache which didn't work. I finally did an update using the factory images where I would get stuck at the boot animation of flying dots. However, at this point I noticed I never performed the unlock step because the bootloader was already unlocked.
How to determine lock status of the boot loader?
The buttons on the device are a bit counter-intuitive in terms of Up and Down volume, but by turning off the device and then holding down the
power + volume up + volume down the device will boot into a menu that allows you to toggle using volume up and down Start, Recovery mode, and provides a list of information about the device including bootloader status. It said the bootloader was unlocked. I assume the previous owner unlocked the bootloader because I don't remember unlocking it.
To finally get the system to boot I had to re-lock the bootloader using the platform-tools provided in the Android SDK.
fastboot oem lock
Then it immediately started. I guess they are taking security more seriously and requiring the bootloader to be locked, but it would be nice if they would tell you.