fsck — Check and Repair File Systems
/usr/sbin/fsck [-F FSType][-m][-V][special...] /usr/sbin/fsck [-F FSType][-n | N | y | Y][-V] [-o FSType-specific-options][special...]
File systems rely on an internal set of tables to keep track of inodes and used and available blocks. When these internal tables are not properly synchronized with data on a disk, inconsistencies result and file systems need to be repaired.
File systems can be damaged or become inconsistent because of abrupt termination of the operating system in the following ways.
Accidental unplugging of the system.
Turning off the system without proper shutdown procedure.
A software error in the kernel.
File-system corruption, though serious, is not common. ...