After a reboot of one of my systems I got the following error:
pivot_root: No such file or directory
/sbin/init: 426:cannot open /dev/console: No such file
Kernel panic - not syncing: Attempted to kill init!
After an upgrade of the kernel via apt-get on debian, the menu.lst entry in grub for the new kernel is pointed to /dev/hda1 by default. If the kernel is on a different partition this error will appear.