sys-utils/umount.8

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  25 .TH UMOUNT 8 "July 2014" "util-linux" "System Administration"
  26 .SH NAME
  27 umount \- unmount file systems
  28 .SH SYNOPSIS
  29 .B umount \-a
  30 .RB [ \-dflnrv ]
  31 .RB [ \-t
  32 .IR fstype ]
  33 .RB [ \-O
  34 .IR option ...]
  35 .sp
  36 .B umount
  37 .RB [ \-dflnrv ]
  38 .RI { directory | device }...
  39 .sp
  40 .B umount
  41 .BR \-h | \-V
  42
  43 .SH DESCRIPTION
  44 The
  45 .B umount
  46 command detaches the mentioned file system(s) from the file hierarchy.  A
  47 file system is specified by giving the directory where it has been
  48 mounted.  Giving the special device on which the file system lives may
  49 also work, but is obsolete, mainly because it will fail in case this
  50 device was mounted on more than one directory.
  51 .PP
  52 Note that a file system cannot be unmounted when it is 'busy' - for
  53 example, when there are open files on it, or when some process has its
  54 working directory there, or when a swap file on it is in use.  The
  55 offending process could even be
  56 .B umount
  57 itself - it opens libc, and libc in its turn may open for example locale
  58 files.  A lazy unmount avoids this problem.
  59 .SH OPTIONS
  60 .TP
  61 .BR \-a , " \-\-all"
  62 All of the filesystems described in
  63 .I /etc/mtab
  64 are unmounted, except the \fIproc\fR filesystem.
  65 .TP
  66 .BR \-A , " \-\-all-targets"
  67 Unmount all mountpoints in the current namespace for the specified filesystem.
  68 The filesystem can be specified by one of the mountpoints or the device name (or
  69 UUID, etc.).  When this option is used together with \fB\-\-recursive\fR, then
  70 all nested mounts within the filesystem are recursively unmounted.
  71 This option is only supported on systems where /etc/mtab is a symlink
  72 to /proc/mounts.
  73 .TP
  74 .BR \-c , " \-\-no-canonicalize"
  75 Do not canonicalize paths.  For more details about this option see the
  76 .BR mount (8)
  77 man page.  Note that \fBumount\fR does not pass this option to the
  78 .BI /sbin/umount. type
  79 helpers.
  80 .TP
  81 .BR \-d , " \-\-detach-loop"
  82 When the unmounted device was a loop device, also free this loop
  83 device.
  84 .TP
  85 .B \-\-fake
  86 Causes everything to be done except for the actual system call; this 'fakes'
  87 unmounting the filesystem.  It can be used to remove entries from
  88 .I /etc/mtab
  89 that were unmounted earlier with the
  90 .B \-n
  91 option.
  92 .TP
  93 .BR \-f , " \-\-force"
  94 Force an unmount (in case of an unreachable NFS system).  (Requires kernel
  95 2.1.116 or later.)
  96 .TP
  97 .BR \-i , " \-\-internal-only"
  98 Do not call the \fB/sbin/umount.\fIfilesystem\fR helper even if it exists.
  99 By default such a helper program is called if it exists.
 100 .TP
 101 .BR \-l , " \-\-lazy"
 102 Lazy unmount.  Detach the filesystem from the file hierarchy now,
 103 and clean up all references to this filesystem as soon as it is not busy
 104 anymore.  (Requires kernel 2.4.11 or later.)
 105 .TP
 106 .BR \-n , " \-\-no-mtab"
 107 Unmount without writing in
 108 .IR /etc/mtab .
 109 .TP
 110 .BR \-O , " \-\-test-opts " \fIoption\fR...
 111 Unmount only the filesystems that have the specified option set in
 112 .IR /etc/fstab .
 113 More than one option may be specified in a comma-separated list.
 114 Each option can be prefixed with
 115 .B no
 116 to indicate that no action should be taken for this option.
 117 .TP
 118 .BR \-R , " \-\-recursive"
 119 Recursively unmount each specified directory.  Recursion for each directory will
 120 stop if any unmount operation in the chain fails for any reason.  The relationship
 121 between mountpoints is determined by /proc/self/mountinfo entries.  The filesystem
 122 must be specified by mountpoint path; a recursive unmount by device name (or UUID)
 123 is unsupported.
 124 .TP
 125 .BR \-r , " \-\-read-only"
 126 When an unmount fails, try to remount the filesystem read-only.
 127 .TP
 128 .BR \-t , " \-\-types " \fItype\fR...
 129 Indicate that the actions should only be taken on filesystems of the
 130 specified
 131 .IR type .
 132 More than one type may be specified in a comma-separated list.  The list
 133 of filesystem types can be prefixed with
 134 .B no
 135 to indicate that no action should be taken for all of the mentioned types.
 136 .TP
 137 .BR \-v , " \-\-verbose"
 138 Verbose mode.
 139 .TP
 140 .BR \-V , " \-\-version"
 141 Display version information and exit.
 142 .TP
 143 .BR \-h , " \-\-help"
 144 Display help text and exit.
 145 .SH "LOOP DEVICE"
 146 The
 147 .B umount
 148 command will free the loop device associated with a mount when
 149 it finds the option \fBloop=...\fR in
 150 .IR /etc/mtab ,
 151 or when the \fB\-d\fR option was given.  Any still associated loop devices
 152 can be freed by using \fBlosetup -d\fR; see
 153 .BR losetup (8).
 154 .SH EXTERNAL HELPERS
 155 The syntax of external unmount helpers is:
 156 .PP
 157 .RS
 158 .BI umount. suffix
 159 .RI { directory | device }
 160 .RB [ \-flnrv ]
 161 .RB [ \-t
 162 .IR type . subtype ]
 163 .RE
 164 .PP
 165 where \fIsuffix\fR is the filesystem type (or the value from a
 166 \fBuhelper=\fR or \fBhelper=\fR marker in the mtab file).
 167 The \fB\-t\fR option can be used for filesystems that
 168 have subtype support.  For example:
 169 .PP
 170 .RS
 171 .B umount.fuse \-t fuse.sshfs
 172 .RE
 173 .PP
 174 A \fBuhelper=\fIsomething\fR marker (unprivileged helper) can appear in
 175 the \fI/etc/mtab\fR file when ordinary users need to be able to unmount
 176 a mountpoint that is not defined in \fI/etc/fstab\fR
 177 (for example for a device that was mounted by \fBudisks\fR(1)).
 178 .PP
 179 A \fBhelper=\fItype\fR marker in the mtab file will redirect
 180 all unmount requests
 181 to the \fB/sbin/umount.\fItype\fR helper independently of UID.
 182 .SH FILES
 183 .TP
 184 .B /etc/mtab
 185 table of mounted filesystems
 186 .TP
 187 .B /etc/fstab
 188 table of known filesystems
 189 .SH ENVIRONMENT
 190 .IP LIBMOUNT_FSTAB=<path>
 191 overrides the default location of the fstab file
 192 .IP LIBMOUNT_MTAB=<path>
 193 overrides the default location of the mtab file
 194 .IP LIBMOUNT_DEBUG=0xffff
 195 enables debug output
 196 .SH "SEE ALSO"
 197 .BR umount (2),
 198 .BR mount (8),
 199 .BR losetup (8)
 200 .SH HISTORY
 201 A
 202 .B umount
 203 command appeared in Version 6 AT&T UNIX.
 204 .SH AVAILABILITY
 205 The umount command is part of the util-linux package and is available from
 206 .UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 207 Linux Kernel Archive
 208 .UE .