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  49 also work, but is obsolete, mainly because it will fail in case this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