I wrote this since I always forget the 2 essential steps in order to regain root on a Nexus 10 device which has been updated over-the-air. Basically you’ll have to flash a new recovery image:

# ~/android-sdk/platform-tools/fastboot flash recovery recovery-clockwork-touch-

Before booting into recovery make sure you’ll push the latest SuperSU zip package to your device:

# adb push UPDATE-SuperSU-v1.51.zip /mnt/sdcard

Boot into recovery:

# adb reboot recovery

In CWRM install the previously pushed zip file and you’re done.