The dreaded Linux server that does not start up after a reboot. There are many online articles on how to fix this but there is also a simple solution that has worked for me.
Boot into the system using a rescue CD / rescue mode on a standard Linux install CD and allow it to mount and chroot you into the server’s root file system.
Then:
# update-grub # grub-install /dev/xvdX # exit # (exit the chroot) # reboot