234 lines
7.9 KiB
Groff
234 lines
7.9 KiB
Groff
.\" Copyright (c) 1996 Andries Brouwer
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.\" This page is somewhat derived from a page that was
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.\" (c) 1980, 1989, 1991 The Regents of the University of California
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.\" and had been heavily modified by Rik Faith and myself.
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License along
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.\" with this program; if not, write to the Free Software Foundation, Inc.,
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.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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.\"
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.TH UMOUNT 8 "July 2014" "util-linux" "System Administration"
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.SH NAME
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umount \- unmount file systems
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.SH SYNOPSIS
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.B umount \-a
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.RB [ \-dflnrv ]
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.RB [ \-t
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.IR fstype ]
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.RB [ \-O
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.IR option ...]
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.sp
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.B umount
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.RB [ \-dflnrv ]
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.RI { directory | device }...
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.sp
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.B umount
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.BR \-h | \-V
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.SH DESCRIPTION
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The
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.B umount
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command detaches the mentioned file system(s) from the file hierarchy. A
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file system is specified by giving the directory where it has been
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mounted. Giving the special device on which the file system lives may
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also work, but is obsolete, mainly because it will fail in case this
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device was mounted on more than one directory.
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.PP
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Note that a file system cannot be unmounted when it is 'busy' - for
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example, when there are open files on it, or when some process has its
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working directory there, or when a swap file on it is in use. The
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offending process could even be
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.B umount
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itself - it opens libc, and libc in its turn may open for example locale
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files. A lazy unmount avoids this problem.
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.SH OPTIONS
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.TP
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.BR \-a , " \-\-all"
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All of the filesystems described in
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.I /proc/self/mountinfo
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(or in deprecated /etc/mtab)
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are unmounted, except the proc, devfs, devpts, sysfs, rpc_pipefs and nfsd
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filesystems. This list of the filesystems may be replaced by \fB\-\-types\fR
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umount option.
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.TP
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.BR \-A , " \-\-all\-targets"
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Unmount all mountpoints in the current namespace for the specified filesystem.
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The filesystem can be specified by one of the mountpoints or the device name (or
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UUID, etc.). When this option is used together with \fB\-\-recursive\fR, then
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all nested mounts within the filesystem are recursively unmounted.
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This option is only supported on systems where /etc/mtab is a symlink
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to /proc/mounts.
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.TP
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.BR \-c , " \-\-no\-canonicalize"
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Do not canonicalize paths. For more details about this option see the
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.BR mount (8)
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man page. Note that \fBumount\fR does not pass this option to the
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.BI /sbin/umount. type
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helpers.
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.TP
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.BR \-d , " \-\-detach\-loop"
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When the unmounted device was a loop device, also free this loop
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device. This option is unnecessary for devices initialized by
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.BR mount (8),
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in this case "autoclear" functionality is enabled by default.
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.TP
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.B \-\-fake
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Causes everything to be done except for the actual system call or umount helper
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execution; this 'fakes' unmounting the filesystem. It can be used to remove
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entries from the deprecated
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.I /etc/mtab
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that were unmounted earlier with the
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.B \-n
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option.
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.TP
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.BR \-f , " \-\-force"
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Force an unmount (in case of an unreachable NFS system). (Requires kernel
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2.1.116 or later.)
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Note that this option does not guarantee that umount command does not hang.
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It's strongly recommended to use absolute paths without symlinks to avoid
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unwanted readlink and stat system calls on unreachable NFS in umount.
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.TP
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.BR \-i , " \-\-internal\-only"
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Do not call the \fB/sbin/umount.\fIfilesystem\fR helper even if it exists.
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By default such a helper program is called if it exists.
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.TP
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.BR \-l , " \-\-lazy"
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Lazy unmount. Detach the filesystem from the file hierarchy now,
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and clean up all references to this filesystem as soon as it is not busy
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anymore. (Requires kernel 2.4.11 or later.)
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.TP
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.BR \-n , " \-\-no\-mtab"
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Unmount without writing in
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.IR /etc/mtab .
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.TP
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.BR \-O , " \-\-test\-opts " \fIoption\fR...
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Unmount only the filesystems that have the specified option set in
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.IR /etc/fstab .
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More than one option may be specified in a comma-separated list.
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Each option can be prefixed with
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.B no
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to indicate that no action should be taken for this option.
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.TP
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.BR \-R , " \-\-recursive"
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Recursively unmount each specified directory. Recursion for each directory will
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stop if any unmount operation in the chain fails for any reason. The relationship
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between mountpoints is determined by /proc/self/mountinfo entries. The filesystem
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must be specified by mountpoint path; a recursive unmount by device name (or UUID)
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is unsupported.
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.TP
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.BR \-r , " \-\-read\-only"
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When an unmount fails, try to remount the filesystem read-only.
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.TP
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.BR \-t , " \-\-types " \fItype\fR...
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Indicate that the actions should only be taken on filesystems of the
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specified
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.IR type .
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More than one type may be specified in a comma-separated list. The list
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of filesystem types can be prefixed with
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.B no
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to indicate that no action should be taken for all of the mentioned types.
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.BR
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Note that
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.B umount
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reads information about mounted filesystems from kernel (/proc/mounts) and
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filesystem names may be different than filesystem names used in the /etc/fstab
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(e.g. "nfs4" vs. "nfs").
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.TP
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.BR \-v , " \-\-verbose"
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Verbose mode.
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.TP
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.BR \-V , " \-\-version"
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Display version information and exit.
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.TP
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.BR \-h , " \-\-help"
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Display help text and exit.
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.SH "LOOP DEVICE"
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The
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.B umount
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command will automatically detach loop device previously initialized by
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.BR mount (8)
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command independently of /etc/mtab.
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In this case the device is initialized with "autoclear" flag (see
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.BR losetup (8)
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output for more details), otherwise it's necessary to use the option \fB \-\-detach\-loop\fR
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or call \fBlosetup -d <device>\fR. The autoclear feature is supported since Linux 2.6.25.
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.SH EXTERNAL HELPERS
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The syntax of external unmount helpers is:
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.PP
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.RS
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.BI umount. suffix
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.RI { directory | device }
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.RB [ \-flnrv ]
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.RB [ \-t
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.IR type . subtype ]
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.RE
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.PP
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where \fIsuffix\fR is the filesystem type (or the value from a
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\fBuhelper=\fR or \fBhelper=\fR marker in the mtab file).
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The \fB\-t\fR option can be used for filesystems that
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have subtype support. For example:
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.PP
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.RS
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.B umount.fuse \-t fuse.sshfs
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.RE
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.PP
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A \fBuhelper=\fIsomething\fR marker (unprivileged helper) can appear in
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the \fI/etc/mtab\fR file when ordinary users need to be able to unmount
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a mountpoint that is not defined in \fI/etc/fstab\fR
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(for example for a device that was mounted by \fBudisks\fR(1)).
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.PP
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A \fBhelper=\fItype\fR marker in the mtab file will redirect
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all unmount requests
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to the \fB/sbin/umount.\fItype\fR helper independently of UID.
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.PP
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Note that \fI/etc/mtab\fR is currently deprecated and helper= and another
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userspace mount options are maintained by libmount.
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.SH FILES
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.TP
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.I /etc/mtab
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table of mounted filesystems (deprecated and usually replaced by
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symlink to /proc/mounts)
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.TP
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.I /etc/fstab
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table of known filesystems
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.TP
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.I /proc/self/mountinfo
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table of mounted filesystems generated by kernel.
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.SH ENVIRONMENT
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.IP LIBMOUNT_FSTAB=<path>
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overrides the default location of the fstab file (ignored for suid)
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.IP LIBMOUNT_MTAB=<path>
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overrides the default location of the mtab file (ignored for suid)
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.IP LIBMOUNT_DEBUG=all
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enables libmount debug output
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.SH "SEE ALSO"
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.BR umount (2),
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.BR losetup (8),
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.BR mount (8)
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.SH HISTORY
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A
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.B umount
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command appeared in Version 6 AT&T UNIX.
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.SH AVAILABILITY
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The umount command is part of the util-linux package and is available from
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.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
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Linux Kernel Archive
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.UE .
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