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.\"     @(#)umount.8	8.2 (Berkeley) 5/8/95
.\"
.Dd September 12, 2016
.Dt UMOUNT 8
.Os
.Sh NAME
.Nm umount
.Nd unmount filesystems
.Sh SYNOPSIS
.Nm
.Op Fl fvFR
.Op Fl t Ar fstypelist
.Ar special | node
.Nm
.Fl a
.Op Fl fvF
.Op Fl h Ar host
.Op Fl t Ar fstypelist
.Sh DESCRIPTION
The
.Nm
command
calls the
.Xr unmount 2
system call (or an external unmount program) to remove a
.Ar "special device"
or the remote node (rhost:path) from the filesystem tree at the point
.Ar node .
If either
.Ar special
or
.Ar node
are not provided, the appropriate information is taken from the
.Xr fstab 5
file.
.Pp
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
.Dq umount .
This matches the form used by the external mount programs used by
.Xr mount 8 .
If this program is found on the path, it is used in preference to
calling
.Xr unmount 2
directly.
Note that in the
.Nx
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.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl a
All the currently mounted filesystems except the root are unmounted.
.It Fl 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.
.It Fl F
Fake the unmount; perform all other processing but do not actually
attempt the unmount.
(This is most useful in conjunction with
.Fl v ,
to see what
.Nm
would attempt to do).
.It Fl R
Take the
.Ar special | node
argument as a path to be passed directly to
.Xr unmount 2 ,
bypassing all attempts to be smart about mechanically determining the
correct path from the argument.
This option is incompatible with any option that potentially unmounts
more than one filesystem, such as
.Fl a ,
but it can be used with
.Fl f
and/or
.Fl 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 program.
.It Fl h Ar host
Only filesystems mounted from the specified host will be
unmounted.
This option is implies the
.Fl a
option and, unless otherwise specified with the
.Fl t
option, will only unmount NFS filesystems.
.It Fl t Ar fstypelist
Is used to indicate the actions should only be taken on
filesystems 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
.Dq no
to specify the filesystem types for which action should
.Em not
be taken.
For example, the
.Nm
command:
.Bd -literal -offset indent
umount -a -t nfs,mfs
.Ed
.Pp
unmounts all filesystems of the type
.Tn NFS
and
.Tn MFS ,
whereas the
.Nm
command:
.Bd -literal -offset indent
umount -a -t nonfs,mfs
.Ed
.Pp
unmounts all file systems except those of type
.Tn NFS
and
.Tn MFS .
.It Fl v
Verbose, additional information is printed out as each filesystem
is unmounted.
.El
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
filesystem table
.El
.Sh SEE ALSO
.Xr unmount 2 ,
.Xr fstab 5 ,
.Xr mount 8
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .