Command Section
UMOUNT(8)               FreeBSD System Manager's Manual              UMOUNT(8)

     umount - unmount file systems

     umount [-fnv] 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
     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

     -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.  Also,
             doing a forced dismount 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
             unmounted.  This option implies the -A option and, unless
             otherwise specified with the -t option, will only unmount NFS
             file systems.

     -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
             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.

     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.)

     /etc/fstab  file system table

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

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

FreeBSD 11.1-RELEASE-p4          July 7, 2016          FreeBSD 11.1-RELEASE-p4
Command Section