Debian 7 amd64 在 Windows 8.1 ent x64 主机上的 VirtualBox 5.0.10 中运行。此 VM 已运行 1 年多。使用基本分区，而不是 LVM 或任何 Raid。
今天突然自动卸载所有磁盘，并以只读模式挂载 /，我在 VirtualBox Manager 上强制重启它。然后它就无法再启动系统了 :doge
GRUB loading.
Welcome to GRUB!
error: out of partition.
Entering rescue mode...
grub rescue> ls
(hd0) (hd0,msdos5) (hd0,msdos1)
grub rescue> ls (hd0,msdos1)/
./ ../ lost+found/ var/ etc/ media/ vmlinuz sbin/ usr/ lib/ lib64/ selinux/ bin/ boot/
proc/ mnt/ tmp/ dev/ home/ root/ sys/ run/ srv/ opt/ initrd.img keybase/ lib32/ core
grub rescue> ls (hd0,msdos1)/boot/
error: out of partition.
grub rescue> ls (hd0)/
error: unknown filesystem
grub rescue> ls (hd0,msdos5)/
error: unknown filesystem
grub rescue> set root=(hd0,msdos1)
grub rescue> set prefix=(hd0,msdos1)/boot/grub
grub rescue> insmod normal
error: out of partition.
grub rescue> normal
Unknow command 'normal'
grub rescue>
我使用 debian-7.11.0-amd64-netinst.iso 进入 Debian 的救援模式，但在最后一步，它无法在任何分区上挂载 /target，显示此警告：
An error occurred while mounting the device you entered for your root file system (/dev/sda1) on /target
Please check the syslog for more information.
/var/log/syslog
rescue-mode: partitions found: /dev/sda1, /dev/sda2, /dev/sda5
rescue-mode: selected root device '/dev/sda1'
rescue: umount: can't umount /target: Invalid argument
kernel: EXT2-fs (sda1): error: couldn't mount because of unsupported optional features (244)
kernel: EXT3-fs (sda1): error: couldn't mount because of unsupported optional features (240)
kernel: EXT4-fs (sda1): ext4_check_descriptors: Block bitmap for group 128 not in group (block 811458560)!
kernel: EXT4-fs (sda1): group descriptors corrupted!
kernel: FAT-fs (sda1): utf8 is not a recommented IO charset for FAT filesystems, filesystem will be case sensitive!
rescue: mount: mounting /dev/sda1 on /target failed: Invalid argument
rescue-mode: mount '/dev/sda1' /target failed
kernel: atkbd serio0: Spurious NAK on isa0060/serio0. Some program migh be trying access hardware directly.
rescue-mode: partitions found: /dev/sda1, /dev/sda2, /dev/sda5
rescue-mode: selected root device '/dev/sda2'
rescue: umount: can't umount /target: Invalid argument
kernel: isofs_fill_super: bread failed, dev=sda2, iso_blknum=16, block=32
kernel: EXT2-fs (sda2): error: unable to read superblock
kernel: EXT3-fs (sda2): error: unable to read superblock
kernel: EXT4-fs (sda2): unable to read superblock
kernel: REISERFS warning (device sda2): sh-2006 read_super_block: bread failed (dev sda2, block 8, size 1024)
kernel: REISERFS warning (device sda2): sh-2006 read_super_block: bread failed (dev sda2, block 64, size 1024)
kernel: FAT-fs (sda2): utf8 is not a recommented IO charset for FAT filesystems, filesystem will be case sensitive!
rescue: mount: mounting /dev/sda2 on /target failed: Invalid argument
rescue-mode: mount '/dev/sda2' /target failed
rescue-mode: partitions found: /dev/sda1, /dev/sda2, /dev/sda5
rescue-mode: selected root device '/dev/sda5'
rescue: umount: can't umount /target: Invalid argument
kernel: FAT-fs (sda5): utf8 is not a recommented IO charset for FAT filesystems, filesystem will be case sensitive!
rescue: mount: mounting /dev/sda5 on /target failed: Invalid argument
rescue-mode: mount '/dev/sda5' /target failed
更新日期：2016-11-14
你是对的DerfK，这是虚拟硬件损坏。
在 Debian 的救援模式下没有挂载任何分区，运行后就fsck.ext4 -ycf /dev/sda1修复了。