1UMOUNT(8)                    System Administration                   UMOUNT(8)
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NAME

6       umount - unmount file systems
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SYNOPSIS

9       umount -a [-dflnrv] [-t fstype] [-O option...]
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11       umount [-dflnrv] {directory|device}...
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13       umount -h|-V
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DESCRIPTION

17       The  umount command detaches the mentioned file system(s) from the file
18       hierarchy.  A file system is specified by giving the directory where it
19       has  been  mounted.  Giving the special device on which the file system
20       lives may also work, but is obsolete, mainly because it  will  fail  in
21       case this device was mounted on more than one directory.
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23       Note  that  a  file  system cannot be unmounted when it is 'busy' - for
24       example, when there are open files on it, or when some process has  its
25       working  directory  there,  or  when  a swap file on it is in use.  The
26       offending process could even be umount itself - it opens libc, and libc
27       in  its  turn may open for example locale files.  A lazy unmount avoids
28       this problem, but it may introduce another issues. See --lazy  descrip‐
29       tion below.
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OPTIONS

32       -a, --all
33              All  of the filesystems described in /proc/self/mountinfo (or in
34              deprecated /etc/mtab) are unmounted,  except  the  proc,  devfs,
35              devpts, sysfs, rpc_pipefs and nfsd filesystems. This list of the
36              filesystems may be replaced by --types umount option.
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38       -A, --all-targets
39              Unmount all mountpoints in the current namespace for the  speci‐
40              fied  filesystem.  The filesystem can be specified by one of the
41              mountpoints or the device  name  (or  UUID,  etc.).   When  this
42              option is used together with --recursive, then all nested mounts
43              within the filesystem are recursively unmounted.  This option is
44              only  supported  on  systems  where  /etc/mtab  is  a symlink to
45              /proc/mounts.
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47       -c, --no-canonicalize
48              Do not canonicalize paths.  The paths canonicalization is  based
49              on  stat(2) and readlink(2) system calls. These system calls may
50              hang in some cases (for example on NFS if server is  not  avail‐
51              able).  The  option  has  to  be used with canonical path to the
52              mount point.
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54              For more details about this option see the  mount(8)  man  page.
55              Note   that   umount   does   not   pass   this  option  to  the
56              /sbin/umount.type helpers.
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58       -d, --detach-loop
59              When the unmounted device was a loop device, also free this loop
60              device.  This  option  is unnecessary for devices initialized by
61              mount(8), in this case "autoclear" functionality is  enabled  by
62              default.
63
64       --fake Causes  everything  to be done except for the actual system call
65              or umount helper execution; this 'fakes' unmounting the filesys‐
66              tem.   It  can  be  used  to  remove entries from the deprecated
67              /etc/mtab that were unmounted earlier with the -n option.
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69       -f, --force
70              Force an unmount (in case of an unreachable NFS system).
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72              Note that this option does not  guarantee  that  umount  command
73              does  not hang.  It's strongly recommended to use absolute paths
74              without symlinks to avoid  unwanted  readlink  and  stat  system
75              calls on unreachable NFS in umount.
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77       -i, --internal-only
78              Do  not  call  the  /sbin/umount.filesystem  helper  even  if it
79              exists.  By default such  a  helper  program  is  called  if  it
80              exists.
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82       -l, --lazy
83              Lazy  unmount.   Detach  the  filesystem from the file hierarchy
84              now, and clean up all references to this filesystem as  soon  as
85              it is not busy anymore.
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87              A system reboot would be expected in near future if you're going
88              to use this option for network filesystem  or  local  filesystem
89              with  submounts.   The  recommended use-case for umount -l is to
90              prevent hangs on shutdown due to an  unreachable  network  share
91              where a normal umount will hang due to a downed server or a net‐
92              work partition. Remounts of the share will not be possible.
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95       -N, --namespace ns
96              Perform umount in namespace specified by ns.  ns is  either  PID
97              of  process running in that namespace or special file represent‐
98              ing that namespace.
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100              umount(8) switches to the namespace when  it  reads  /etc/fstab,
101              writes  /etc/mtab  (or writes to /run/mount) and calls umount(2)
102              system call, otherwise it runs in  the  original  namespace.  It
103              means  that  the  target  namespace does not have to contain any
104              libraries or another requirements necessary to execute umount(2)
105              command.
106
107              See namespaces(7) for more information.
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109       -n, --no-mtab
110              Unmount without writing in /etc/mtab.
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112       -O, --test-opts option...
113              Unmount  only the filesystems that have the specified option set
114              in /etc/fstab.  More than one  option  may  be  specified  in  a
115              comma-separated  list.   Each  option can be prefixed with no to
116              indicate that no action should be taken for this option.
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118       -q, --quiet
119              Suppress "not mounted" error messages.
120
121       -R, --recursive
122              Recursively unmount each  specified  directory.   Recursion  for
123              each  directory  will stop if any unmount operation in the chain
124              fails for any reason.  The relationship between  mountpoints  is
125              determined by /proc/self/mountinfo entries.  The filesystem must
126              be specified by mountpoint path; a recursive unmount  by  device
127              name (or UUID) is unsupported.
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129       -r, --read-only
130              When an unmount fails, try to remount the filesystem read-only.
131
132       -t, --types type...
133              Indicate that the actions should only be taken on filesystems of
134              the specified type.  More than one type may be  specified  in  a
135              comma-separated  list.  The list of filesystem types can be pre‐
136              fixed with no to indicate that no action should be taken for all
137              of  the  mentioned  types.   Note  that umount reads information
138              about  mounted  filesystems  from  kernel   (/proc/mounts)   and
139              filesystem  names may be different than filesystem names used in
140              the /etc/fstab (e.g. "nfs4" vs. "nfs").
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142       -v, --verbose
143              Verbose mode.
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145       -V, --version
146              Display version information and exit.
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148       -h, --help
149              Display help text and exit.
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LOOP DEVICE

152       The umount command will automatically  detach  loop  device  previously
153       initialized by mount(8) command independently of /etc/mtab.
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155       In  this case the device is initialized with "autoclear" flag (see los‐
156       etup(8) output for more details), otherwise it's necessary to  use  the
157       option   --detach-loop  or call losetup -d <device>. The autoclear fea‐
158       ture is supported since Linux 2.6.25.
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EXTERNAL HELPERS

161       The syntax of external unmount helpers is:
162
163              umount.suffix {directory|device}  [-flnrv]  [-N  namespace]  [-t
164              type.subtype]
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166       where  suffix  is  the filesystem type (or the value from a uhelper= or
167       helper= marker in the mtab file).   The  -t  option  can  be  used  for
168       filesystems that have subtype support.  For example:
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170              umount.fuse -t fuse.sshfs
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172       A  uhelper=something  marker  (unprivileged  helper)  can appear in the
173       /etc/mtab file when ordinary users need to be able to unmount a  mount‐
174       point  that is not defined in /etc/fstab (for example for a device that
175       was mounted by udisks(1)).
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177       A helper=type marker  in  the  mtab  file  will  redirect  all  unmount
178       requests to the /sbin/umount.type helper independently of UID.
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180       Note  that  /etc/mtab  is  currently deprecated and helper= and another
181       userspace mount options are maintained by libmount.
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FILES

184       /etc/mtab
185              table of mounted filesystems (deprecated and usually replaced by
186              symlink to /proc/mounts)
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188       /etc/fstab
189              table of known filesystems
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191       /proc/self/mountinfo
192              table of mounted filesystems generated by kernel.
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ENVIRONMENT

195       LIBMOUNT_FSTAB=<path>
196              overrides  the  default  location of the fstab file (ignored for
197              suid)
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199       LIBMOUNT_MTAB=<path>
200              overrides the default location of the  mtab  file  (ignored  for
201              suid)
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203       LIBMOUNT_DEBUG=all
204              enables libmount debug output
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SEE ALSO

207       umount(2), losetup(8), mount(8)
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HISTORY

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

213       The  umount  command is part of the util-linux package and is available
214       from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
215       linux/⟩.
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219util-linux                         July 2014                         UMOUNT(8)
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