freebsd man page for umount

UMOUNT(8)						    BSD System Manager's Manual 						 UMOUNT(8)

NAME
     umount -- unmount file systems

SYNOPSIS
     umount [-fv] special ... | node ... | fsid ...
     umount -a | -A [-F fstab] [-fv] [-h host] [-t type]

DESCRIPTION
     The umount utility calls the unmount(2) system call to remove a file system from the file system tree.  The file system can be specified by
     its special device or remote node (rhost:path), the path to the mount point node or by the file system ID fsid as reported by ``mount -v''
     when run by root.

     The options are as follows:

     -a      All the file systems described in fstab(5) are unmounted.

     -A      All the currently mounted file systems except the root are unmounted.

     -F fstab
	     Specify the fstab file to use.

     -f      The file system is forcibly unmounted.  Active special devices continue to work, but all other files return errors if further
	     accesses are attempted.  The root file system cannot be forcibly unmounted.  For NFS, a forced dismount can take up to 1 minute or
	     more to complete against an unresponsive server and may throw away data not yet written to the server for this case.

     -h host
	     Only file systems mounted from the specified host will be unmounted.  This option implies the -A option and, unless otherwise speci-
	     fied with the -t option, will only unmount NFS file systems.

     -t type
	     Is used to indicate the actions should only be taken on file systems of the specified type.  More than one type may be specified in a
	     comma separated list.  The list of file system types can be prefixed with ``no'' to specify the file system types for which action
	     should not be taken.  For example, the umount command:

		   umount -a -t nfs,nullfs

	     unmounts all file systems of the type NFS and NULLFS that are listed in the fstab(5) file.

     -v      Verbose, additional information is printed out as each file system is unmounted.

ENVIRONMENT
     PATH_FSTAB  If the environment variable PATH_FSTAB is set, all operations are performed against the specified file.  PATH_FSTAB will not be
		 honored if the process environment or memory address space is considered ``tainted''.	(See issetugid(2) for more information.)

FILES
     /etc/fstab  file system table

SEE ALSO
     unmount(2), fstab(5), autounmountd(8), mount(8)

HISTORY
     A umount utility appeared in Version 6 AT&T UNIX.

BSD
								 November 22, 2014							       BSD