307 lines
10 KiB
Groff
307 lines
10 KiB
Groff
.\" 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 "July 2014" "util-linux" "System Administration"
|
|
.SH NAME
|
|
umount \- unmount filesystems
|
|
.SH SYNOPSIS
|
|
.B umount \-a
|
|
.RB [ \-dflnrv ]
|
|
.RB [ \-t
|
|
.IR fstype ]
|
|
.RB [ \-O
|
|
.IR option ...]
|
|
.sp
|
|
.B umount
|
|
.RB [ \-dflnrv ]
|
|
.RI { directory | device }...
|
|
.sp
|
|
.B umount
|
|
.BR \-h | \-V
|
|
|
|
.SH DESCRIPTION
|
|
The
|
|
.B umount
|
|
command detaches the mentioned filesystem(s) from the file hierarchy. A
|
|
filesystem is specified by giving the directory where it has been
|
|
mounted. Giving the special device on which the filesystem 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also work, but is obsolete, mainly because it will fail in case this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 filesystem 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, but it may introduce other
|
|
issues. See \fB\-\-lazy\fR description below.
|
|
.SH OPTIONS
|
|
.TP
|
|
.BR \-a , " \-\-all"
|
|
All of the filesystems described in
|
|
.I /proc/self/mountinfo
|
|
(or in deprecated
|
|
.IR /etc/mtab )
|
|
are unmounted, except the proc, devfs, devpts, sysfs, rpc_pipefs and nfsd
|
|
filesystems. This list of the filesystems may be replaced by \fB\-\-types\fR
|
|
umount option.
|
|
.TP
|
|
.BR \-A , " \-\-all\-targets"
|
|
Unmount all mountpoints in the current mount namespace
|
|
for the specified filesystem.
|
|
The filesystem can be specified by one of the mountpoints or the device name (or
|
|
UUID, etc.). When this option is used together with \fB\-\-recursive\fR, then
|
|
all nested mounts within the filesystem are recursively unmounted.
|
|
This option is only supported on systems where
|
|
.I /etc/mtab
|
|
is a symlink
|
|
to
|
|
.IR /proc/mounts .
|
|
.TP
|
|
.BR \-c , " \-\-no\-canonicalize"
|
|
Do not canonicalize paths. The paths canonicalization is based on
|
|
.BR stat (2)
|
|
and
|
|
.BR readlink (2)
|
|
system calls. These system calls may hang in some cases (for example on NFS if
|
|
server is not available). The option has to be used with canonical path to the
|
|
mount point.
|
|
|
|
For more details about this option see the
|
|
.BR mount (8)
|
|
man page. Note that \fBumount\fR does not pass this option to the
|
|
.BI /sbin/umount. type
|
|
helpers.
|
|
.TP
|
|
.BR \-d , " \-\-detach\-loop"
|
|
When the unmounted device was a loop device, also free this loop
|
|
device. This option is unnecessary for devices initialized by
|
|
.BR mount (8),
|
|
in this case "autoclear" functionality is enabled by default.
|
|
.TP
|
|
.B \-\-fake
|
|
Causes everything to be done except for the actual system call or umount helper
|
|
execution; this 'fakes' unmounting the filesystem. It can be used to remove
|
|
entries from the deprecated
|
|
.I /etc/mtab
|
|
that were unmounted earlier with the
|
|
.B \-n
|
|
option.
|
|
.TP
|
|
.BR \-f , " \-\-force"
|
|
Force an unmount (in case of an unreachable NFS system).
|
|
|
|
Note that this option does not guarantee that umount command does not hang.
|
|
It's strongly recommended to use absolute paths without symlinks to avoid
|
|
unwanted readlink and stat system calls on unreachable NFS in umount.
|
|
.TP
|
|
.BR \-i , " \-\-internal\-only"
|
|
Do not call the \fB/sbin/umount.\fIfilesystem\fR helper even if it exists.
|
|
By default such a helper program is called if it exists.
|
|
.TP
|
|
.BR \-l , " \-\-lazy"
|
|
Lazy unmount. Detach the filesystem from the file hierarchy now,
|
|
and clean up all references to this filesystem as soon as it is not busy
|
|
anymore.
|
|
|
|
A system reboot would be expected in near future if you're going to use this
|
|
option for network filesystem or local filesystem with submounts. The
|
|
recommended use-case for \fBumount \-l\fR is to prevent hangs on shutdown due to
|
|
an unreachable network share where a normal umount will hang due to a downed
|
|
server or a network partition. Remounts of the share will not be possible.
|
|
|
|
.TP
|
|
.BR \-N , " \-\-namespace " \fIns
|
|
Perform umount in the mount namespace specified by \fIns\fR.
|
|
\fIns\fR is either PID of process running in that namespace
|
|
or special file representing that namespace.
|
|
.sp
|
|
.BR umount (8)
|
|
switches to the namespace when it reads
|
|
.IR /etc/fstab ,
|
|
writes
|
|
.I /etc/mtab
|
|
(or writes to
|
|
.IR /run/mount )
|
|
and calls
|
|
.BR umount (2)
|
|
system call, otherwise it runs in the original namespace.
|
|
It means that the target mount namespace does not have
|
|
to contain any libraries or other requirements necessary to execute
|
|
.BR umount (2)
|
|
command.
|
|
.sp
|
|
See \fBmount_namespaces\fR(7) for more information.
|
|
.TP
|
|
.BR \-n , " \-\-no\-mtab"
|
|
Unmount without writing in
|
|
.IR /etc/mtab .
|
|
.TP
|
|
.BR \-O , " \-\-test\-opts " \fIoption\fR...
|
|
Unmount only the filesystems that have the specified option set in
|
|
.IR /etc/fstab .
|
|
More than one option may be specified in a comma-separated list.
|
|
Each option can be prefixed with
|
|
.B no
|
|
to indicate that no action should be taken for this option.
|
|
.TP
|
|
.BR \-q , " \-\-quiet"
|
|
Suppress "not mounted" error messages.
|
|
.TP
|
|
.BR \-R , " \-\-recursive"
|
|
Recursively unmount each specified directory. Recursion for each directory will
|
|
stop if any unmount operation in the chain fails for any reason. The relationship
|
|
between mountpoints is determined by
|
|
.I /proc/self/mountinfo
|
|
entries. The filesystem
|
|
must be specified by mountpoint path; a recursive unmount by device name (or UUID)
|
|
is unsupported.
|
|
.TP
|
|
.BR \-r , " \-\-read\-only"
|
|
When an unmount fails, try to remount the filesystem read-only.
|
|
.TP
|
|
.BR \-t , " \-\-types " \fItype\fR...
|
|
Indicate that the actions should only be taken on filesystems of the
|
|
specified
|
|
.IR type .
|
|
More than one type may be specified in a comma-separated list. The list
|
|
of filesystem types can be prefixed with
|
|
.B no
|
|
to indicate that no action should be taken for all of the mentioned types.
|
|
Note that
|
|
.B umount
|
|
reads information about mounted filesystems from kernel (/proc/mounts) and
|
|
filesystem names may be different than filesystem names used in the
|
|
.I /etc/fstab
|
|
(e.g., "nfs4" vs. "nfs").
|
|
.TP
|
|
.BR \-v , " \-\-verbose"
|
|
Verbose mode.
|
|
.TP
|
|
.BR \-V , " \-\-version"
|
|
Display version information and exit.
|
|
.TP
|
|
.BR \-h , " \-\-help"
|
|
Display help text and exit.
|
|
.SH NON-SUPERUSER UMOUNTS
|
|
Normally, only the superuser can umount filesystems.
|
|
However, when
|
|
.I fstab
|
|
contains the
|
|
.B user
|
|
option on a line, anybody can umount the corresponding filesystem. For more details see
|
|
.BR mount (8)
|
|
man page.
|
|
.PP
|
|
Since version 2.34 the \fBumount\fR command can be used to
|
|
perform umount operation also
|
|
for fuse filesystems if kernel mount table contains user's ID. In this case fstab
|
|
user= mount option is not required.
|
|
.PP
|
|
Since version 2.35 \fBumount\fR command does not exit when user permissions are
|
|
inadequate by internal libmount security rules. It drops suid permissions
|
|
and continue as regular non-root user.
|
|
This can be used to support use-cases where
|
|
root permissions are not necessary (e.g., fuse filesystems, user namespaces,
|
|
etc).
|
|
.SH LOOP DEVICE
|
|
The
|
|
.B umount
|
|
command will automatically detach loop device previously initialized by
|
|
.BR mount (8)
|
|
command independently of
|
|
.IR /etc/mtab .
|
|
|
|
In this case the device is initialized with "autoclear" flag (see
|
|
.BR losetup (8)
|
|
output for more details), otherwise it's necessary to use the option \fB \-\-detach\-loop\fR
|
|
or call \fBlosetup \-d <device>\fR. The autoclear feature is supported since Linux 2.6.25.
|
|
.SH EXTERNAL HELPERS
|
|
The syntax of external unmount helpers is:
|
|
.PP
|
|
.RS
|
|
.BI umount. suffix
|
|
.RI { directory | device }
|
|
.RB [ \-flnrv ]
|
|
.RB [ \-N
|
|
.IR namespace ]
|
|
.RB [ \-t
|
|
.IR type . subtype ]
|
|
.RE
|
|
.PP
|
|
where \fIsuffix\fR is the filesystem type (or the value from a
|
|
\fBuhelper=\fR or \fBhelper=\fR marker in the mtab file).
|
|
The \fB\-t\fR option can be used for filesystems that
|
|
have subtype support. For example:
|
|
.PP
|
|
.RS
|
|
.B umount.fuse \-t fuse.sshfs
|
|
.RE
|
|
.PP
|
|
A \fBuhelper=\fIsomething\fR marker (unprivileged helper) can appear in
|
|
the \fI/etc/mtab\fR file when ordinary users need to be able to unmount
|
|
a mountpoint that is not defined in \fI/etc/fstab\fR
|
|
(for example for a device that was mounted by \fBudisks\fR(1)).
|
|
.PP
|
|
A \fBhelper=\fItype\fR marker in the mtab file will redirect
|
|
all unmount requests
|
|
to the \fB/sbin/umount.\fItype\fR helper independently of UID.
|
|
.PP
|
|
Note that \fI/etc/mtab\fR is currently deprecated and helper= and other
|
|
userspace mount options are maintained by libmount.
|
|
.SH ENVIRONMENT
|
|
.IP LIBMOUNT_FSTAB=<path>
|
|
overrides the default location of the fstab file (ignored for suid)
|
|
.IP LIBMOUNT_MTAB=<path>
|
|
overrides the default location of the mtab file (ignored for suid)
|
|
.IP LIBMOUNT_DEBUG=all
|
|
enables libmount debug output
|
|
.SH FILES
|
|
.TP
|
|
.I /etc/mtab
|
|
table of mounted filesystems (deprecated and usually replaced by
|
|
symlink to
|
|
.IR /proc/mounts )
|
|
.TP
|
|
.I /etc/fstab
|
|
table of known filesystems
|
|
.TP
|
|
.I /proc/self/mountinfo
|
|
table of mounted filesystems generated by kernel.
|
|
.SH HISTORY
|
|
A
|
|
.B umount
|
|
command appeared in Version 6 AT&T UNIX.
|
|
.SH SEE ALSO
|
|
.BR umount (2),
|
|
.BR losetup (8),
|
|
.BR mount_namespaces (7)
|
|
.BR mount (8)
|
|
.SH AVAILABILITY
|
|
The umount command is part of the util-linux package and is available from
|
|
.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
|
|
Linux Kernel Archive
|
|
.UE .
|