cloud-initramfs-rescuevol binary package in Ubuntu Precise amd64

 This package adds functionality to an initramfs built by initramfs-tools.
 When installed the initramfs will check to see if any partitions
 with a label of 'RESCUE_VOL' are attached. If such a volume is attached,
 it will boot off that volume rather than the root volume.
 .
 This is useful in a cloud environment, when the user is able to attach
 and detach volumes to a running system, but has no other mechanism
 for interupting of fixing a failed boot. It is analogous to inserting
 a rescue CD into a system to recover from failure.

Source package