180 lines
5.2 KiB
Groff
180 lines
5.2 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 "March 2010" "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
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.RB [ \-hV ]
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.LP
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.B umount \-a
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.RB [ \-dflnrv ]
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.RB [ \-t
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.IR vfstype ]
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.RB [ \-O
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.IR options ]
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.br
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.B umount
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.RB [ \-dflnrv ]
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.RI { dir | device }...
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.SH DESCRIPTION
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The
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.B umount
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command detaches the file system(s) mentioned from the file hierarchy.
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A file system is specified by giving the directory where it
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has been mounted. Giving the special device on which the file system lives
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may also work, but is obsolete, mainly because it will fail
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in case this device was mounted on more than one directory.
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Note that a file system cannot be unmounted when it is `busy' -
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for example, when there are open files on it, or when some process
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has its working directory there, or when a swap file on it is in use.
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The 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
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locale files.
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A lazy unmount avoids this problem.
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Options for the
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.B umount
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command:
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.TP
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.B \-V
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Print version and exit.
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.TP
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.B \-h
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Print help message and exit.
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.TP
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.B \-v
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Verbose mode.
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.TP
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.B \-n
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Unmount without writing in
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.IR /etc/mtab .
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.TP
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.B \-r
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In case unmounting fails, try to remount read-only.
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.TP
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.B \-d
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In case the unmounted device was a loop device, also
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free this loop device.
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.TP
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.B \-i
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Don't call the /sbin/umount.<filesystem> helper even if it exists. By default /sbin/umount.<filesystem> helper is called if one exists.
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.TP
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.B \-a
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All of the file systems described in
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.I /etc/mtab
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are unmounted. (With
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.B umount
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version 2.7 and later: the
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.I proc
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filesystem is not unmounted.)
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.TP
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.BI \-t " vfstype"
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Indicate that the actions should only be taken on file systems of the
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specified type. More than one type may be specified in a comma separated
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list. The list of file system types can be prefixed with
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.B no
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to specify the file system types on which no action should be taken.
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.TP
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.BI \-O " options"
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Indicate that the actions should only be taken on file systems with
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the specified options in
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.IR /etc/fstab .
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More than one option type may be specified in a comma separated
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list. Each option can be prefixed with
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.B no
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to specify options for which no action should be taken.
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.TP
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.B \-f
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Force unmount (in case of an unreachable NFS system).
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(Requires kernel 2.1.116 or later.)
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.TP
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.B \-l
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Lazy unmount. Detach the filesystem from the filesystem hierarchy now,
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and cleanup all references to the filesystem as soon as it is not busy
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anymore.
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(Requires kernel 2.4.11 or later.)
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.IP "\fB\-\-no\-canonicalize\fP"
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Don't canonicalize paths. For more details about this option see the
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.BR mount (8)
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man page.
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.IP "\fB\-\-fake\fP"
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Causes everything to be done except for the actual system call; this
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``fakes'' unmounting the filesystem. It can be used to remove
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entries from
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.I /etc/mtab
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that were unmounted earlier with the -n option.
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.SH "THE LOOP DEVICE"
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The
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.B umount
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command will free the loop device (if any) associated
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with the mount, in case it finds the option `loop=...' in
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.IR /etc/mtab ,
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or when the \-d option was given.
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Any pending loop devices can be freed using `losetup -d', see
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.BR losetup (8).
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.SH NOTES
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The syntax of external umount helpers is:
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.br
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.BI /sbin/umount. <suffix>
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.RI { dir | device }
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.RB [ \-nlfvr ]
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.RB [ \-t
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.IR type.subtype ]
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.br
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where the <suffix> is filesystem type or a value from "uhelper=" or "helper="
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mtab option. The \-t option is used for filesystems with subtypes support
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(for example /sbin/mount.fuse -t fuse.sshfs).
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The uhelper= (unprivileged umount helper) is possible to use when non-root user
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wants to umount a mountpoint which is not defined in the /etc/fstab file (e.g
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devices mounted by udisk).
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The helper= mount option redirects all umount requests to the
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/sbin/umount.<helper> independently on UID.
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.SH FILES
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.I /etc/mtab
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table of mounted file systems
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.SH "SEE ALSO"
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.BR umount (2),
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.BR mount (8),
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.BR losetup (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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ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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