Running a File System Check

If your Linux box suddenly loses power, or your laptop battery dies, or your external drive dock gets disconnected, it's possible that your harddrive needs to have it's filesystem checked.  Here is how to do this for ext3-formatted and ext4-formatted drives.

Plug in the hard drive to the computer and open a terminal.

Become root:

shell$ su -

Password:

root#

See which drive was recently attached, in case you're unsure

root# dmesg

...

...

...

[1144639.292844] sd 24:0:0:0: [sde] No Caching mode page present

[1144639.292855] sd 24:0:0:0: [sde] Assuming drive cache: write through

[1144639.356633]  sde: sde1

shell#

Unless you know what you're doing with filesystem fragments and the like (I do not), you probably just want this up and working rather than trying to recover tiny parts of files.  We see the above 'dmesg' output telling us the newest attached partition is 'sde1' so we'll run a filesystem check against that partition.

First, make sure the drive isn't mounted or you can cause issues:

WARNING!!!  The filesystem is mounted.   If you continue you ***WILL*** cause ***SEVERE*** filesystem damage.

If you're sure the drive isn't mounted (run as root 'umount /dev/sde1'), let's proceed:

Run the auto repair (-p) first, then we'll force (-f) a second run and auto-answer Yes (-y) to any questions:

root# fsck -p /dev/sde1

...

root# fsck -f -y /dev/sde1

fsck from util-linux 2.20.1e2

fsck 1.42 (29-Nov-2011)

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 (721019450, counted=301927649).Fix? yes

Free inodes count wrong (183148533, counted=183148043).Fix? yes

DriveName: ***** FILE SYSTEM WAS MODIFIED *****

DriveName: 501/183148544 files (3.4% non-contiguous), 430638623/732566272 blocks

root# 

If you have 'bad blocks' errors you may want to run a 'bad block check' and we'll answer 'yes' to these questions as well:

root# fsck -c -y /dev/sde1 

Did this work out for you?  Let us know in the comments!