umount(8) - NetBSD Manual Pages

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


NAME

     umount -- unmount filesystems


SYNOPSIS

     umount [-fvFR] [-t fstypelist] special | node
     umount -a [-fvF] [-h host] [-t fstypelist]


DESCRIPTION

     The umount command calls the unmount(2) system call (or an external
     unmount program) to remove a special device or the remote node
     (rhost:path) from the filesystem tree at the point node.  If either
     special or node are not provided, the appropriate information is taken
     from the fstab(5) file.

     By default, the file system type is extracted from the kernel and used to
     choose an external unmount program, whose name is formed by appending an
     underscore and the type string to ``umount''.  This matches the form used
     by the external mount programs used by mount(8).  If this program is
     found on the path, it is used in preference to calling unmount(2)
     directly.  Note that in the NetBSD base system no such external unmount
     programs exist; the facility is provided in the hopes that it will be
     useful for third party file systems and/or for research.

     The options are as follows:

     -a      All the currently mounted filesystems except the root are
             unmounted.

     -f      The filesystem is forcibly unmounted.  Active special devices
             continue to work, but all other files return errors if further
             accesses are attempted.  The root filesystem cannot be forcibly
             unmounted.

     -F      Fake the unmount; perform all other processing but do not actu-
             ally attempt the unmount.  (This is most useful in conjunction
             with -v, to see what umount would attempt to do).

     -R      Take the special | node argument as a path to be passed directly
             to unmount(2), bypassing all attempts to be smart about mechani-
             cally determining the correct path from the argument.  This
             option is incompatible with any option that potentially unmounts
             more than one filesystem, such as -a, but it can be used with -f
             and/or -v.  This is the only way to unmount something that does
             not appear as a directory (such as a nullfs mount of a plain
             file); there are probably other cases where it is necessary.
             This option also disables the use of any external unmount pro-
             gram.

     -h host
             Only filesystems mounted from the specified host will be
             unmounted.  This option is implies the -a option and, unless oth-
             erwise specified with the -t option, will only unmount NFS
             filesystems.

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

                   umount -a -t nfs,mfs

             unmounts all filesystems of the type NFS and MFS, whereas the
             umount command:

                   umount -a -t nonfs,mfs

             unmounts all file systems except those of type NFS and MFS.

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


FILES

     /etc/fstab  filesystem table


SEE ALSO

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


HISTORY

     A umount command appeared in Version 1 AT&T UNIX.

NetBSD 8.3                    September 12, 2016                    NetBSD 8.3