fsck

• Linux fsck utility is used to check and repair Linux filesystems
• EXT2, EXT3, EXT4, etc
• The system sometimes run fsck during boot time to check whether the fs is in consistent state
• fsck must be run in unmounted file systems! To avoid data corruption
• fsck is run on the filesystem, not on the mounted on

fsck "/dev/sdx1"
fsck "/dev/sdx1" -f # force system check even if it is clean
fsck "/dev/sdx1" -y # fix problems automatically
fsck "/dev/mapper/lol" # encrypted device (unlocked and unmounted)

• Exit codes for fsck. echo $? to see the code
• 0: No errors
• 1: fs errors corrected
• 2: system must be rebooted
• 4: fs errors left uncorrected
• 8: operational error
• 16: usage or syntax error
• 32: fsck canceled by user request
• 128: Shared-library error

xfs_repair

• Similar to fsck but for XFS file systems
• Unlike fsck, it does not run at boot time
• For large partitions. Terabytes

# Unmount the filesystem first
umount /data # /data is the folder in which the FS is mounted

# Repair
xfs_repair "filesystem"
xfs_repair /dev/sdx1

# Mount it back
mount /dev/sdx1 /data