10 Practical fsck Commands to Diagnose and Repair Linux Filesystems

Linux fsck is a utility for checking and repairing Linux file systems (ext2, ext3, ext4, etc.). It runs automatically at boot if a file system has not been checked recently, and administrators can invoke it manually on unmounted file systems to avoid data loss.

1. Checking a file system on a disk partition

First, list all available partitions with # parted /dev/sda print:

# parted /dev/sda print

Number  Start   End     Size    Type      File system  Flags
1      1049kB  106MB   105MB   primary   fat16        diag
2      106MB   15.8GB  15.7GB  primary   ntfs         boot
3      15.8GB  266GB   251GB   primary   ntfs
4      266GB   500GB   234GB   extended
5      266GB   466GB   200GB   logical   ext4
6      467GB   486GB   18.3GB  logical   ext2
7      487GB   499GB   12.0GB  logical   fat32        lba

Then run # fsck /dev/sda6 to check a specific file system:

# fsck /dev/sda6
fsck from util-linux 2.20.1
e2fsck 1.42 (29-Nov-2011)
/dev/sda6: clean, 95/2240224 files, 3793506/4476416 blocks

2. File‑system‑specific fsck commands

fsck

calls the appropriate checker (e.g., fsck.ext2, fsck.ext3, fsck.ext4) located in /sbin:

# cd /sbin
# ls fsck*
fsck  fsck.cramfs  fsck.ext2  fsck.ext3  fsck.ext4  fsck.ext4dev  fsck.minix  fsck.msdos  fsck.nfs  fsck.vfat

If the checker for a file system is missing (e.g., fsck.ntfs), fsck reports an error.

# fsck /dev/sda2
fsck from util-linux 2.20.1
fsck: fsck.ntfs: not found
fsck: error 2 while executing fsck.ntfs for /dev/sda2

3. Using -A to check all file systems in one run

The -A option checks every file system listed in /etc/fstab in the order of their fs_passno values. Filesystems with a pass number of 0 are skipped.

# cat /etc/fstab

##
proc            /proc           proc    nodev,noexec,nosuid 0       0
/dev/sda5       /               ext4    errors=remount-ro   0       1
/dev/sda6       /mydata         ext2    defaults            0       2
/dev/sda7       /backup         vfat    defaults            0       3

Run the global check: # fsck -A It is recommended to add -R to skip the root file system:

# fsck -AR -y

4. Using -t to check only specific file‑system types

The -t option limits the check to the listed types. For example, to check only ext2 file systems: # fsck -AR -t ext2 -y To exclude a type, prefix it with no (e.g., noext2).

5. Avoid running fsck on mounted file systems with -M

Use -M as the default to prevent accidental checks on mounted partitions:

# mount | grep "/dev/sd*"
/dev/sda5 on / type ext4 (rw,errors=remount-ro)
/dev/sda6 on /mydata type ext2 (rw)
/dev/sda7 on /backup type vfat (rw)
# fsck -M /dev/sda7
# echo $?
0

6. Skipping the title line with -T

The -T option suppresses the introductory line printed by fsck:

# fsck -TAR
...

7. Forcing a check with -f even on a clean file system

By default, fsck skips clean file systems. Use -f to force a full check:

# fsck /dev/sda6 -f
...

8. Automatically fixing detected problems with -y

The -y option answers “yes” to all prompts, repairing errors without user interaction:

# fsck -y /dev/sda6
...

9. Reporting problems without fixing them using -n

The -n option prints detected issues to standard output but makes no changes:

# fsck -n /dev/sda6
...

10. Automatic repair of corrupt parts with -a

The -a option behaves like e2fsck -p, automatically fixing safe problems. If a serious issue is found, fsck exits with code 4.

# fsck -a -AR
...

For more severe inconsistencies, use -y to force full automatic repair.