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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 program; if not, write to the Free Software Foundation, Inc.,
.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
.\"
.TH UMOUNT 8 "August 2012" "util-linux" "System Administration"
.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also work, but is obsolete, mainly because it will fail in case this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.
.PP
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.
.SH OPTIONS
.TP
\fB\-a\fR, \fB\-\-all\fR
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
\fB\-c\fR, \fB\-\-no\-canonicalize\fR
Do not canonicalize paths. For more details about this option see the
.B mount(8)
man page.
.TP
\fB\-d\fR, \fB\-\-detach\-loop\fR
In case the unmounted device was a loop device, also free this loop
device.
.TP
\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
.B \-n
option.
.TP
\fB\-f\fR, \fB\-\-force\fR
Force unmount (in case of an unreachable NFS system). (Requires kernel
2.1.116 or later.)
.TP
\fB\-i\fR, \fB\-\-internal\-only\fR
Do not call the /sbin/umount.<filesystem> helper even if it exists. By
default /sbin/umount.<filesystem> helper is called if one exists.
.TP
\fB\-n\fR, \fB\-\-no\-mtab\fR
Unmount without writing in
.IR /etc/mtab .
.TP
\fB\-l\fR, \fB\-\-lazy\fR
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.)
.TP
\fB\-O\fR, \fB\-\-test\-opts\fR \fIoptions,list\fR
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
\fB\-r\fR, \fB\-\-read\-only\fR
In case unmounting fails, try to remount read-only.
.TP
\fB\-t\fR, \fB\-\-types\fR \fIvfstype,ext2,ext3\fR
Indicate that the actions should only be taken on file systems of the
specified
.IR 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
\fB\-v\fR, \fB\-\-verbose\fR
Verbose mode.
.TP
\fB\-h\fR, \fB\-\-help\fR
Print help message and exit.
.TP
\fB\-V\fR, \fB\-\-version\fR
Print version and exit.
.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:
.PP
.BI /sbin/umount. <suffix>
.RI { dir | device }
.RB [ \-nlfvr ]
.RB [ \-t
.IR type.subtype ]
.PP
where the <suffix> is filesystem type or a value from "uhelper=" or
"helper=" mtab option. The \-t option is used for filesystems with
subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).
.PP
The uhelper= (unprivileged umount helper) is possible to use when
non-root user wants to umount a mountpoint which is not defined in the
/etc/fstab file (e.g. devices mounted by udisk).
.PP
The helper= mount option redirects all umount requests to the
/sbin/umount.<helper> independently on UID.
.SH FILES
.I /etc/mtab
table of mounted file systems
.SH ENVIRONMENT
.IP LIBMOUNT_FSTAB=<path>
overrides the default location of the fstab file
.IP LIBMOUNT_MTAB=<path>
overrides the default location of the mtab file
.IP LIBMOUNT_DEBUG=0xffff
enables debug output
.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 package and is available from
.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .
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