linux fix the superblock by dumpe2fs fsck

Posted 2020-11-04 szllq2000

It seems that you have a bad superblock. To fix this:

Firstly, boot into a live CD or USB

Find out your partition number by using

sudo fdisk -l|grep Linux|grep -Ev ‘swap‘

Then, list all superblocks by using the command:

sudo dumpe2fs /dev/sda2 | grep superblock

Replace sda2 to your drive number

You should get a similar output like this

  Primary superblock at 0, Group descriptors at 1-6
  Backup superblock at 32768, Group descriptors at 32769-32774
  Backup superblock at 98304, Group descriptors at 98305-98310
  Backup superblock at 163840, Group descriptors at 163841-163846
  Backup superblock at 229376, Group descriptors at 229377-229382
  Backup superblock at 294912, Group descriptors at 294913-294918
  Backup superblock at 819200, Group descriptors at 819201-819206
  Backup superblock at 884736, Group descriptors at 884737-884742
  Backup superblock at 1605632, Group descriptors at 1605633-1605638
  Backup superblock at 2654208, Group descriptors at 2654209-2654214
  Backup superblock at 4096000, Group descriptors at 4096001-4096006
  Backup superblock at 7962624, Group descriptors at 7962625-7962630
  Backup superblock at 11239424, Group descriptors at 11239425-11239430
  Backup superblock at 20480000, Group descriptors at 20480001-20480006
  Backup superblock at 23887872, Group descriptors at 23887873-23887878

Choose an alternate superblock from this list, for this case alternate superblock # 32768

Now, to check and repair a Linux file system using alternate superblock # 32768:

sudo fsck -b 32768 /dev/sda2 -y

The -y flag is used to skip all the Fix? questions and to answer them all with a yes automatically

You should get similar output like this:

fsck 1.40.2 (12-Jul-2007)
e2fsck 1.40.2 (12-Jul-2007)
/dev/sda2 was not cleanly unmounted, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Free blocks count wrong for group #241 (32254, counted=32253).
Fix? yes
Free blocks count wrong for group #362 (32254, counted=32248).
Fix? yes
Free blocks count wrong for group #368 (32254, counted=27774).
Fix? yes
..........
/dev/sda2: ***** FILE SYSTEM WAS MODIFIED *****
/dev/sda2: 59586/30539776 files (0.6% non-contiguous), 3604682/61059048 blocks

Now try mounting the partition

sudo mount /dev/sda2 /mnt

Now, try to browse the filesystem with the following commands

cd /mnt
mkdir test
ls -l
cp file /path/to/safe/location

If you are able to perform the above commands, you have most probably fixed your error.

Now, restart you computer and you should be able to boot normally.