刚刚从 13.03 升级到 Ubuntu 14.04，但系统无法启动！
屏幕上显示：
udevadm trigger is not permitted while udev is unconfigured.
Gave up waiting for root device. Common Problems:
Boot args (cat/proc/cmdline)
Check rootdelay= (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/dd1dad95-9bd3-429e-8e94-3f1d49da20e7 does not exist.
Dropping to a shell!
Busybox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built-in shell (ash)
Enter 'help' for a list of built-in commands.
(initramfs) _