fsck in action on a Linux system. The system utility fsck (for  f ile s ystem c onsistency chec k ) is a tool for checking the consistency of a file system in Unix and Unix-like operating systems, such as Linux and OS X.sck in action on a Linux system. The system utility fsck (for  f ile s ystem c onsistency chec k ) is a tool for checking the consistency of a file system in Unix and Unix-like operating systems, such as Linux and OS X.