ubuntu ashell fsck

意外断电以后，系统文件损坏，系统无法启动，进入了 ashell ，尝试exit 报错提示如下：

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/mapper/emgda--vg-root does not exist.   
Dropping to a shell! 

BusyBox v.1.22.1 (Ubuntu 1:1.22.0-15ubuntu1.4) built-in shell (ash)   
Enter 'help' for list of built-in commands.  

(initramfs)

fsck 工具进行修复，然后系统可以进入

fsck /dev/mapper/emgda--vg-root -y

硬盘的分区格式是ext4的

fsck.ext4 -yf /dev/mapper/emgda--vg-root