LinuxReviws.org --get your your Linux knowledge
> Linux Reviews > Manual Pages (man) >

umount

, umount2 unmount file system


  1. umount.2.man
  2. umount.8.man


1. umount.2.man

Manpage of UMOUNT

UMOUNT

Section: Linux Programmer's Manual (2)
Updated: 2010-06-19
Index Return to Main Contents
 

NAME

umount, umount2 - unmount file system  

SYNOPSIS

#include <sys/mount.h>

int umount(const char *target);

int umount2(const char *target, int flags);
 

DESCRIPTION

umount() and umount2() remove the attachment of the (topmost) file system mounted on target.

Appropriate privilege (Linux: the CAP_SYS_ADMIN capability) is required to unmount file systems.

Linux 2.1.116 added the umount2() system call, which, like umount(), unmounts a target, but allows additional flags controlling the behavior of the operation:

MNT_FORCE (since Linux 2.1.116)
Force unmount even if busy. This can cause data loss. (Only for NFS mounts.)
MNT_DETACH (since Linux 2.4.11)
Perform a lazy unmount: make the mount point unavailable for new accesses, and actually perform the unmount when the mount point ceases to be busy.
MNT_EXPIRE (since Linux 2.6.8)
Mark the mount point as expired. If a mount point is not currently in use, then an initial call to umount2() with this flag fails with the error EAGAIN, but marks the mount point as expired. The mount point remains expired as long as it isn't accessed by any process. A second umount2() call specifying MNT_EXPIRE unmounts an expired mount point. This flag cannot be specified with either MNT_FORCE or MNT_DETACH.
UMOUNT_NOFOLLOW (since Linux 2.6.34)
Don't dereference target if it is a symbolic link. This flag allows security problems to be avoided in set-user-ID-root programs that allow unprivileged users to unmount file systems.
 

RETURN VALUE

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.  

ERRORS

The error values given below result from file-system type independent errors. Each file system type may have its own special errors and its own special behavior. See the kernel source code for details.
EAGAIN
A call to umount2() specifying MNT_EXPIRE successfully marked an unbusy file system as expired.
EBUSY
target could not be unmounted because it is busy.
EFAULT
target points outside the user address space.
EINVAL
target is not a mount point. Or, umount2() was called with MNT_EXPIRE and either MNT_DETACH or MNT_FORCE.
ENAMETOOLONG
A pathname was longer than MAXPATHLEN.
ENOENT
A pathname was empty or had a nonexistent component.
ENOMEM
The kernel could not allocate a free page to copy filenames or data into.
EPERM
The caller does not have the required privileges.
 

VERSIONS

MNT_DETACH and MNT_EXPIRE are only available in glibc since version 2.11.  

CONFORMING TO

These functions are Linux-specific and should not be used in programs intended to be portable.  

NOTES

The original umount() function was called as umount(device) and would return ENOTBLK when called with something other than a block device. In Linux 0.98p4 a call umount(dir) was added, in order to support anonymous devices. In Linux 2.3.99-pre7 the call umount(device) was removed, leaving only umount(dir) (since now devices can be mounted in more than one place, so specifying the device does not suffice).  

SEE ALSO

mount(2), path_resolution(7), mount(8), umount(8)  

COLOPHON

This page is part of release 3.32 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

This document was created by man2html using the manual pages.
Time: 17:32:53 GMT, October 23, 2013

2. umount.8.man

Manpage of UMOUNT

UMOUNT

Section: Linux Programmer's Manual (8)
Updated: 26 July 1997
Index Return to Main Contents
 

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 package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
THE LOOP DEVICE
NOTES
FILES
SEE ALSO
HISTORY
AVAILABILITY

This document was created by man2html using the manual pages.
Time: 17:32:54 GMT, October 23, 2013

ENGLISH - ENGLISH - ENGLISH - ENGLISH - ja - nl - pl - ENGLISH

Meet new people