After I backed up my ubuntu 12.04, my system crashed

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http://askubuntu.com – Outline: I use the way shown on http://ubuntuforums.org/showthread.php?t=35087 to backup my linux system, but somehow when I restore it, it crashes. Problem Description: When I reboot, there's an information: Gave up waiting for root device. Common problems: -- Boot args (cat /proc/cmdline) -- Check rootdisplay = (did the system wait long enough?) -- Check root = (did the system wait for the right device?) -- Missing modules (cat /proc/modules; ls dev) ALERT! /dev/disk/by-uuid/9cf6f563-86d1-47be-bc26-92dd7df35cb3 does not exist. Dropping to a shell! (HowTos)