umount(8)

1UMOUNT(8)                  Linux Programmer's Manual                 UMOUNT(8)
2
3
4

NAME

6       umount - unmount file systems
7

SYNOPSIS

9       umount [-hV]
10
11       umount -a [-dflnrv] [-t vfstype] [-O options]
12       umount [-dflnrv] dir | device [...]
13

DESCRIPTION

15       The  umount command detaches the file system(s) mentioned from the file
16       hierarchy.  A file system is specified by giving the directory where it
17       has  been  mounted.  Giving the special device on which the file system
18       lives may also work, but is obsolete, mainly because it  will  fail  in
19       case this device was mounted on more than one directory.
20
21       Note  that  a  file  system cannot be unmounted when it is `busy' - for
22       example, when there are open files on it, or when some process has  its
23       working  directory  there,  or  when  a swap file on it is in use.  The
24       offending process could even be umount itself - it opens libc, and libc
25       in  its  turn may open for example locale files.  A lazy unmount avoids
26       this problem.
27
28       Options for the umount command:
29
30       -V     Print version and exit.
31
32       -h     Print help message and exit.
33
34       -v     Verbose mode.
35
36       -n     Unmount without writing in /etc/mtab.
37
38       -r     In case unmounting fails, try to remount read-only.
39
40       -d     In case the unmounted device was a loop device, also  free  this
41              loop device.
42
43       -i     Don't  call  the  /sbin/umount.<filesystem>  helper  even  if it
44              exists. By default /sbin/umount.<filesystem> helper is called if
45              one exists.
46
47       -a     All  of  the  file systems described in /etc/mtab are unmounted.
48              (With umount version 2.7 and later: the proc filesystem  is  not
49              unmounted.)
50
51       -t vfstype
52              Indicate  that  the actions should only be taken on file systems
53              of the specified type.  More than one type may be specified in a
54              comma separated list.  The list of file system types can be pre‐
55              fixed with no to specify the  file  system  types  on  which  no
56              action should be taken.
57
58       -O options
59              Indicate  that  the actions should only be taken on file systems
60              with the specified options in /etc/fstab.  More than one  option
61              type  may  be  specified in a comma separated list.  Each option
62              can be prefixed with no to specify options for which  no  action
63              should be taken.
64
65       -f     Force unmount (in case of an unreachable NFS system).  (Requires
66              kernel 2.1.116 or later.)
67
68       -l     Lazy unmount. Detach the filesystem from the filesystem  hierar‐
69              chy now, and cleanup all references to the filesystem as soon as
70              it is not busy anymore.  (Requires kernel 2.4.11 or later.)
71
72

THE LOOP DEVICE

74       The umount command will free the loop device (if any)  associated  with
75       the mount, in case it finds the option `loop=...' in /etc/mtab, or when
76       the -d option was given.  Any pending loop devices can be  freed  using
77       `losetup -d', see losetup(8).
78
79

NOTES

81       The syntax of external umount helpers is:
82
83       /sbin/umount.<suffix> [-nlfvr] dir | device
84
85       where  the  <suffix> is filesystem type or a value from "uhelper=" mtab
86       option.
87
88       The uhelper (unprivileged umount request helper) is possible used  when
89       non-root  user wants to umount a mountpoint which is not defined in the
90       /etc/fstab file (e.g devices mounted by HAL).
91
92

FILES

94       /etc/mtab table of mounted file systems
95
96

HISTORY

102       A umount command appeared in Version 6 AT&T UNIX.
103
104
105
106Linux 2.0                        26 July 1997                        UMOUNT(8)