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.\" Copyright (c) 1996 Andries Brouwer
.\" This page is somewhat derived from a page that was
.\" (c) 1980, 1989, 1991 The Regents of the University of California
.\" and had been heavily modified by Rik Faith and myself.
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
.\" USA.
.\"
.TH UMOUNT 8 "26 July 1997" "Linux 2.0" "Linux Programmer's Manual"
.SH NAME
umount \- unmount file systems
.SH SYNOPSIS
.B umount
.RB [ \-hV ]
.LP
.B umount \-a
.RB [ \-dflnrv ]
.RB [ \-t
.IR vfstype ]
.RB [ \-O
.IR options ]
.br
.B umount
.RB [ \-dflnrv ]
.RI { dir | device }...
.SH DESCRIPTION
The
.B umount
command detaches the file system(s) mentioned from the file hierarchy.
A file system is specified by giving the directory where it
has been mounted. Giving the special device on which the file system lives
may also work, but is obsolete, mainly because it will fail
in case this device was mounted on more than one directory.
Note that a file system cannot be unmounted when it is `busy' -
for example, when there are open files on it, or when some process
has its working directory there, or when a swap file on it is in use.
The offending process could even be
.B umount
itself - it opens libc, and libc in its turn may open for example
locale files.
A lazy unmount avoids this problem.
Options for the
.B umount
command:
.TP
.B \-V
Print version and exit.
.TP
.B \-h
Print help message and exit.
.TP
.B \-v
Verbose mode.
.TP
.B \-n
Unmount without writing in
.IR /etc/mtab .
.TP
.B \-r
In case unmounting fails, try to remount read-only.
.TP
.B \-d
In case the unmounted device was a loop device, also
free this loop device.
.TP
.B \-i
Don't call the /sbin/umount.<filesystem> helper even if it exists. By default /sbin/umount.<filesystem> helper is called if one exists.
.TP
.B \-a
All of the file systems described in
.I /etc/mtab
are unmounted. (With
.B umount
version 2.7 and later: the
.I proc
filesystem is not unmounted.)
.TP
.BI \-t " vfstype"
Indicate that 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
.B no
to specify the file system types on which no action should be taken.
.TP
.BI \-O " options"
Indicate that the actions should only be taken on file systems with
the specified options in
.IR /etc/fstab .
More than one option type may be specified in a comma separated
list. Each option can be prefixed with
.B no
to specify options for which no action should be taken.
.TP
.B \-f
Force unmount (in case of an unreachable NFS system).
(Requires kernel 2.1.116 or later.)
.TP
.B \-l
Lazy unmount. Detach the filesystem from the filesystem hierarchy now,
and cleanup all references to the filesystem as soon as it is not busy
anymore.
(Requires kernel 2.4.11 or later.)
.IP "\fB\-\-no\-canonicalize\fP"
Don't canonicalize paths. For more details about this option see the
.B mount(8)
man page.
.IP "\fB\-\-fake\fP"
Causes everything to be done except for the actual system call; this
``fakes'' unmounting the filesystem. It can be used to remove
entries from
.I /etc/mtab
that were unmounted earlier with the -n option.
.SH "THE LOOP DEVICE"
The
.B umount
command will free the loop device (if any) associated
with the mount, in case it finds the option `loop=...' in
.IR /etc/mtab ,
or when the \-d option was given.
Any pending loop devices can be freed using `losetup -d', see
.BR losetup (8).
.SH NOTES
The syntax of external umount helpers is:
.br
.BI /sbin/umount. <suffix>
.RI { dir | device }
.RB [ \-nlfvr ]
.br
where the <suffix> is filesystem type or a value from "uhelper=" mtab option.
The uhelper (unprivileged umount helper) is possible to used when non-root user
wants to umount a mountpoint which is not defined in the /etc/fstab file (e.g
devices mounted by HAL).
.SH FILES
.I /etc/mtab
table of mounted file systems
.SH "SEE ALSO"
.BR umount (2),
.BR mount (8),
.BR losetup (8).
.SH HISTORY
A
.B umount
command appeared in Version 6 AT&T UNIX.
.SH AVAILABILITY
The umount command is part of the util-linux-ng package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
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