The FSCK (file system check) command checks a file system for errors.
Important! You need to unmount the filesystem before checking filesystem for errors. You cannot unmount the / (root) filesystem.
In this example, the /dev/sda2 partition is unmounted, then checked for errors, and then remounted. If fsck is able to locate corrupted files, the files will be placed in the /lost+found directory.
~]# umount /dev/sda2 ~]# fsck -C /dev/sda2 ~]# mount /dev/sda2
By default, fsck will do a quick scan. Using the -f (full) option makes fsck run a full scan.
~]# umount /dev/sda2 ~]# fsck -f /dev/sda2 ~]# mount /dev/sda2
Check file systems in /etc/fstab
The -A option can be used to check every filesystem in /etc/fstab that has a 1 or 2 in the sixth field, such as: /dev/sda2 /home ext4 defaults 0 1. The -R option skips the / (root) filesystem, just in case the / (root) filesystem has read/write.
~]# umount /dev/sda2 ~]# fsck -AR ~]# mount /dev/sda2
Disable interactive prompt
By default, fsck has an interactive prompt, where you will be asked to press Y to fix an issue or N to ignore an issue. The -a or -y options can be used to disable the interactive prompt. This is useful when writing shell scripts.
~]# umount /dev/sda2 ~]# fsck -y /dev/sda2 ~]# mount /dev/sda2