1UMOUNT(8)                  Linux Programmer's Manual                 UMOUNT(8)
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NAME

6       umount - unmount file systems
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SYNOPSIS

9       umount [-hV]
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11       umount -a [-dflnrv] [-t vfstype] [-O options]
12       umount [-dflnrv] {dir|device}...
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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18       lives may also work, but is obsolete, mainly because it  will  fail  in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.
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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.
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28       Options for the umount command:
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30       -V     Print version and exit.
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32       -h     Print help message and exit.
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34       -v     Verbose mode.
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36       -n     Unmount without writing in /etc/mtab.
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38       -r     In case unmounting fails, try to remount read-only.
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40       -d     In case the unmounted device was a loop device, also  free  this
41              loop device.
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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.
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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.)
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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.
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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.
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65       -f     Force unmount (in case of an unreachable NFS system).  (Requires
66              kernel 2.1.116 or later.)
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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.)
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72       --no-canonicalize
73              Don't canonicalize paths. For more details about this option see
74              the mount(8) man page.
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76       --fake Causes  everything  to be done except for the actual system call
77              or  umount  helper  execution;  this  ``fakes''  unmounting  the
78              filesystem.   It  can   be used to remove entries from /etc/mtab
79              that were unmounted earlier with the -n option.
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THE LOOP DEVICE

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

90       The syntax of external umount helpers is:
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92       /sbin/umount.<suffix> {dir|device} [-nlfvr] [-t type.subtype]
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94       where  the  <suffix> is filesystem type or a value from "uhelper=" mtab
95       option.  The -t option is used  for filesystems with  subtypes  support
96       (for example /sbin/mount.fuse -t fuse.sshfs).
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98       The  uhelper (unprivileged umount helper) is possible to used when non-
99       root user wants to umount a mountpoint which  is  not  defined  in  the
100       /etc/fstab file (e.g devices mounted by HAL).
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FILES

104       /etc/mtab table of mounted file systems
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SEE ALSO

108       umount(2), mount(8), losetup(8).
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HISTORY

112       A umount command appeared in Version 6 AT&T UNIX.
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AVAILABILITY

115       The  umount  command is part of the util-linux-ng package and is avail‐
116       able from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
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120Linux 2.0                        26 July 1997                        UMOUNT(8)
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