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UMOUNT


Section: Linux Programmer’s Manual (8)
Updated: 26 July 1997
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NAME

umount – unmount file systems
 

SYNOPSIS

umount

[-hV]

umount -a

[-dflnrv]

[-t

vfstype]

[-O

options]


umount

[-dflnrv]

{dir|device}…

 

DESCRIPTION

The
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may also work, but is obsolete, mainly because it will fail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
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
umount

command:


-V


Print version and exit.
-h


Print help message and exit.
-v


Verbose mode.
-n


Unmount without writing in
/etc/mtab.

-r


In case unmounting fails, try to remount read-only.
-d


In case the unmounted device was a loop device, also
free this loop device.
-i


Don’t call the /sbin/umount.<filesystem> helper even if it exists. By default /sbin/umount.<filesystem> helper is called if one exists.
-a


All of the file systems described in
/etc/mtab

are unmounted. (With
umount

version 2.7 and later: the
proc

filesystem is not unmounted.)

-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
no

to specify the file system types on which no action should be taken.

-O options


Indicate that the actions should only be taken on file systems with
the specified options in
/etc/fstab.

More than one option type may be specified in a comma separated
list. Each option can be prefixed with
no

to specify options for which no action should be taken.

-f


Force unmount (in case of an unreachable NFS system).
(Requires kernel 2.1.116 or later.)
-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.)
–no-canonicalize

Don’t canonicalize paths. For more details about this option see the
mount(8)

man page.

–fake

Causes everything to be done except for the actual system call; this
“fakes” unmounting the filesystem. It can be used to remove
entries from
/etc/mtab

that were unmounted earlier with the -n option.



 

THE LOOP DEVICE

The
umount

command will free the loop device (if any) associated
with the mount, in case it finds the option `loop=…’ in
/etc/mtab,

or when the -d option was given.
Any pending loop devices can be freed using `losetup -d’, see
losetup(8).


 

NOTES

The syntax of external umount helpers is:



/sbin/umount.<suffix>

{dir|device}

[-nlfvr]

[-t

type.subtype]



where the <suffix> is filesystem type or a value from "uhelper=" mtab option.
The -t option is used for filesystems with subtypes support (for example
/sbin/mount.fuse -t fuse.sshfs).


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).


 

FILES

/etc/mtab

table of mounted file systems


 

SEE ALSO

umount(2),

mount(8),

losetup(8).


 

HISTORY

A
umount

command appeared in Version 6 AT&T UNIX.
 

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/.



 

Index



NAME

SYNOPSIS

DESCRIPTION

THE LOOP DEVICE

NOTES

FILES

SEE ALSO

HISTORY

AVAILABILITY



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