check and repair MS-DOS filesystems

-w  Write changes to disk immediately.

-r  Interactively  repair  the  filesystem.  The user is asked for advice whenever there is more than one
    approach to fix an inconsistency.

-l  List path names of files being processed.

-a  Automatically  repair  the filesystem. No user intervention is necessary. Whenever there is more than
    one method to solve a problem, the least destructive approach is used.

-v  Verbose mode. Generates slightly more output.

-t  Mark unreadable clusters as bad.