Where is fsck?

When fsck is run, an executable in either the /usr/sbin or /bin directory known as fsck is run but this is not the real fsck. fsck is just only a dispatcher which invokes a file system type-specific fsck utility.

When Should an fsck run?

Generally, the user required not run fsck. The system runs it automatically whenever the user tries to mount a file system at boot time which is corrupted. Through, problems can creep up. Hardware and Software glitches do occur from time to time. To run fsck it is advicable just after performing the monthly backups.

CAUTION

It is much better to run fsck after the backup rather than before. If fsck finds main problems, it could leave the file system in a worser shape than it was prior to running.