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  49 also work, but is obsolete, mainly because it will fail in case this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 or umount helper
  87 execution; this 'fakes' unmounting the filesystem.  It can be used to remove
  88 entries from
  89 .I /etc/mtab
  90 that were unmounted earlier with the
  91 .B \-n
  92 option.
  93 .TP
  94 .BR \-f , " \-\-force"
  95 Force an unmount (in case of an unreachable NFS system).  (Requires kernel
  96 2.1.116 or later.)
  97 .TP
  98 .BR \-i , " \-\-internal\-only"
  99 Do not call the \fB/sbin/umount.\fIfilesystem\fR helper even if it exists.
 100 By default such a helper program is called if it exists.
 101 .TP
 102 .BR \-l , " \-\-lazy"
 103 Lazy unmount.  Detach the filesystem from the file hierarchy now,
 104 and clean up all references to this filesystem as soon as it is not busy
 105 anymore.  (Requires kernel 2.4.11 or later.)
 106 .TP
 107 .BR \-n , " \-\-no\-mtab"
 108 Unmount without writing in
 109 .IR /etc/mtab .
 110 .TP
 111 .BR \-O , " \-\-test\-opts " \fIoption\fR...
 112 Unmount only the filesystems that have the specified option set in
 113 .IR /etc/fstab .
 114 More than one option may be specified in a comma-separated list.
 115 Each option can be prefixed with
 116 .B no
 117 to indicate that no action should be taken for this option.
 118 .TP
 119 .BR \-R , " \-\-recursive"
 120 Recursively unmount each specified directory.  Recursion for each directory will
 121 stop if any unmount operation in the chain fails for any reason.  The relationship
 122 between mountpoints is determined by /proc/self/mountinfo entries.  The filesystem
 123 must be specified by mountpoint path; a recursive unmount by device name (or UUID)
 124 is unsupported.
 125 .TP
 126 .BR \-r , " \-\-read\-only"
 127 When an unmount fails, try to remount the filesystem read-only.
 128 .TP
 129 .BR \-t , " \-\-types " \fItype\fR...
 130 Indicate that the actions should only be taken on filesystems of the
 131 specified
 132 .IR type .
 133 More than one type may be specified in a comma-separated list.  The list
 134 of filesystem types can be prefixed with
 135 .B no
 136 to indicate that no action should be taken for all of the mentioned types.
 137 .TP
 138 .BR \-v , " \-\-verbose"
 139 Verbose mode.
 140 .TP
 141 .BR \-V , " \-\-version"
 142 Display version information and exit.
 143 .TP
 144 .BR \-h , " \-\-help"
 145 Display help text and exit.
 146 .SH "LOOP DEVICE"
 147 The
 148 .B umount
 149 command will free the loop device associated with a mount when
 150 it finds the option \fBloop=...\fR in
 151 .IR /etc/mtab ,
 152 or when the \fB\-d\fR option was given.  Any still associated loop devices
 153 can be freed by using \fBlosetup -d\fR; see
 154 .BR losetup (8).
 155 .SH EXTERNAL HELPERS
 156 The syntax of external unmount helpers is:
 157 .PP
 158 .RS
 159 .BI umount. suffix
 160 .RI { directory | device }
 161 .RB [ \-flnrv ]
 162 .RB [ \-t
 163 .IR type . subtype ]
 164 .RE
 165 .PP
 166 where \fIsuffix\fR is the filesystem type (or the value from a
 167 \fBuhelper=\fR or \fBhelper=\fR marker in the mtab file).
 168 The \fB\-t\fR option can be used for filesystems that
 169 have subtype support.  For example:
 170 .PP
 171 .RS
 172 .B umount.fuse \-t fuse.sshfs
 173 .RE
 174 .PP
 175 A \fBuhelper=\fIsomething\fR marker (unprivileged helper) can appear in
 176 the \fI/etc/mtab\fR file when ordinary users need to be able to unmount
 177 a mountpoint that is not defined in \fI/etc/fstab\fR
 178 (for example for a device that was mounted by \fBudisks\fR(1)).
 179 .PP
 180 A \fBhelper=\fItype\fR marker in the mtab file will redirect
 181 all unmount requests
 182 to the \fB/sbin/umount.\fItype\fR helper independently of UID.
 183 .SH FILES
 184 .TP
 185 .B /etc/mtab
 186 table of mounted filesystems
 187 .TP
 188 .B /etc/fstab
 189 table of known filesystems
 190 .SH ENVIRONMENT
 191 .IP LIBMOUNT_FSTAB=<path>
 192 overrides the default location of the fstab file (ignored for suid)
 193 .IP LIBMOUNT_MTAB=<path>
 194 overrides the default location of the mtab file (ignored for suid)
 195 .IP LIBMOUNT_DEBUG=all
 196 enables libmount debug output
 197 .SH "SEE ALSO"
 198 .BR umount (2),
 199 .BR mount (8),
 200 .BR losetup (8)
 201 .SH HISTORY
 202 A
 203 .B umount
 204 command appeared in Version 6 AT&T UNIX.
 205 .SH AVAILABILITY
 206 The umount command is part of the util-linux package and is available from
 207 .UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 208 Linux Kernel Archive
 209 .UE .