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

     umount -- unmount file systems

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

     The umount	utility	calls the unmount(2) system call to remove a file sys-
     tem 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

     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	un-

     -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.  If	a
	     process, such as umount without the -f flag is hung on an NFS
	     mount point, use the -N flag instead.  Also, doing	a forced dis-
	     mount of an NFSv3 mount when rpc.lockd(8) is running is unsafe
	     and can result in a crash.

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

     -N	     Do	a forced dismount of an	NFS mount point	without	checking the
	     mount path.  This option can only be used with the	path to	the
	     mount point node and the path must	be specified exactly as	it was
	     at	mount time.  This option is useful when	a process is hung
	     waiting for an unresponsive NFS server while holding a vnode lock
	     on	the mounted-on vnode, such that	umount with the	-f flag	can't
	     complete.	Using this option can result in	a loss of file updates
	     that have not been	flushed	to the NFS server.

     -n	     Unless the	-f is used, the	umount will not	unmount	an active file
	     system.  It will, however,	perform	a flush.  This flag disables
	     this behaviour, preventing	the flush if there are any files open.

     -t	type
	     Is	used to	indicate the actions should only be taken on file sys-
	     tems 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 ac-
	     tion 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 sys-
	     tem is unmounted.

     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

     /etc/fstab	 file system table

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

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

BSD				 July 25, 2017				   BSD


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