sys-utils/umount.8

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  25 .TH UMOUNT 8 "August 2012" "util-linux" "System Administration"
  26 .SH NAME
  27 umount \- unmount file systems
  28 .SH SYNOPSIS
  29 .B umount
  30 .RB [ \-hV ]
  31 .LP
  32 .B umount \-a
  33 .RB [ \-dflnrv ]
  34 .RB [ \-t
  35 .IR vfstype ]
  36 .RB [ \-O
  37 .IR options ]
  38 .br
  39 .B umount
  40 .RB [ \-dflnrv ]
  41 .RI { dir | device }...
  42 .SH DESCRIPTION
  43 The
  44 .B umount
  45 command detaches the file system(s) mentioned from the file hierarchy.  A
  46 file system is specified by giving the directory where it has been
  47 mounted.  Giving the special device on which the file system lives may
  48 also work, but is obsolete, mainly because it will fail in case this
  49 device was mounted on more than one directory.
  50 .PP
  51 Note that a file system cannot be unmounted when it is 'busy' - for
  52 example, when there are open files on it, or when some process has its
  53 working directory there, or when a swap file on it is in use.  The
  54 offending process could even be
  55 .B umount
  56 itself - it opens libc, and libc in its turn may open for example locale
  57 files.  A lazy unmount avoids this problem.
  58 .SH OPTIONS
  59 .TP
  60 \fB\-a\fR, \fB\-\-all\fR
  61 All of the file systems described in
  62 .I /etc/mtab
  63 are unmounted.  (With
  64 .B umount
  65 version 2.7 and later: the
  66 .I proc
  67 filesystem is not unmounted.)
  68 .TP
  69 \fB\-A\fR, \fB\-\-all-targets\fR
  70 Unmount all mountpoints in the current namespace for the specified filesystem.
  71 The filesystem could be specified by one of the mountpoints or device name (or
  72 UUID, etc.). This option could be used together with \fB\-\-recursive\fR then
  73 all nested mounts within the filesystem are recursively unmounted. The
  74 \fB\-\-all-targets\fR is only supported on systems where /etc/mtab is a symlink
  75 to /proc/mounts.
  76 .TP
  77 \fB\-c\fR, \fB\-\-no\-canonicalize\fR
  78 Do not canonicalize paths.  For more details about this option see the
  79 .BR mount (8)
  80 man page. Note that umount(8) does not pass this option to /sbin/umount.<type> helpers.
  81 .TP
  82 \fB\-d\fR, \fB\-\-detach\-loop\fR
  83 In case the unmounted device was a loop device, also free this loop
  84 device.
  85 .TP
  86 \fB\-\-fake\fP
  87 Causes everything to be done except for the actual system call; this 'fakes'
  88 unmounting the filesystem.  It can be used to remove entries from
  89 .I /etc/mtab
  90 that were unmounted earlier with the
  91 .B \-n
  92 option.
  93 .TP
  94 \fB\-f\fR, \fB\-\-force\fR
  95 Force unmount (in case of an unreachable NFS system).  (Requires kernel
  96 2.1.116 or later.)
  97 .TP
  98 \fB\-i\fR, \fB\-\-internal\-only\fR
  99 Do not call the /sbin/umount.<filesystem> helper even if it exists.  By
 100 default /sbin/umount.<filesystem> helper is called if one exists.
 101 .TP
 102 \fB\-n\fR, \fB\-\-no\-mtab\fR
 103 Unmount without writing in
 104 .IR /etc/mtab .
 105 .TP
 106 \fB\-l\fR, \fB\-\-lazy\fR
 107 Lazy unmount.  Detach the filesystem from the filesystem hierarchy now,
 108 and cleanup all references to the filesystem as soon as it is not busy
 109 anymore.  (Requires kernel 2.4.11 or later.)
 110 .TP
 111 \fB\-O\fR, \fB\-\-test\-opts\fR \fIoptions,list\fR
 112 Indicate that the actions should only be taken on file systems with the
 113 specified options in
 114 .IR /etc/fstab .
 115 More than one option type may be specified in a comma separated list.
 116 Each option can be prefixed with
 117 .B no
 118 to specify options for which no action should be taken.
 119 .TP
 120 \fB\-R\fR, \fB\-\-recursive\fR
 121 Recursively unmount each directory specified. Recursion for each directory will
 122 stop if any unmount operation in the chain fails for any reason. The relationship
 123 between mountpoints is determined by /proc/self/mountinfo entries. The filesystem
 124 must be specified by mountpoint path, recursive unmount by device name (or UUID)
 125 is unsupported.
 126 .TP
 127 \fB\-r\fR, \fB\-\-read\-only\fR
 128 In case unmounting fails, try to remount read-only.
 129 .TP
 130 \fB\-t\fR, \fB\-\-types\fR \fIvfstype,ext2,ext3\fR
 131 Indicate that the actions should only be taken on file systems of the
 132 specified
 133 .IR type .
 134 More than one type may be specified in a comma separated list.  The list
 135 of file system types can be prefixed with
 136 .B no
 137 to specify the file system types on which no action should be taken.
 138 .TP
 139 \fB\-v\fR, \fB\-\-verbose\fR
 140 Verbose mode.
 141 .TP
 142 \fB\-h\fR, \fB\-\-help\fR
 143 Display help text and exit.
 144 .TP
 145 \fB\-V\fR, \fB\-\-version\fR
 146 Display version information and exit.
 147 .SH "THE LOOP DEVICE"
 148 The
 149 .B umount
 150 command will free the loop device (if any) associated with the mount, in
 151 case it finds the option 'loop=...' in
 152 .IR /etc/mtab ,
 153 or when the \-d option was given.  Any pending loop devices can be freed
 154 using 'losetup -d', see
 155 .BR losetup (8).
 156 .SH "EXTERNAL HELPERS"
 157 The syntax of external umount helpers is:
 158 .PP
 159 .BI /sbin/umount. <suffix>
 160 .RI { dir | device }
 161 .RB [ \-nlfvr ]
 162 .RB [ \-t
 163 .IR type.subtype ]
 164 .PP
 165 where the <suffix> is filesystem type or a value from "uhelper=" or
 166 "helper=" mtab option.  The \-t option is used for filesystems with
 167 subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).
 168 .PP
 169 The uhelper= (unprivileged umount helper) is possible to use when
 170 non-root user wants to umount a mountpoint which is not defined in the
 171 /etc/fstab file (e.g. devices mounted by udisk).
 172 .PP
 173 The helper= mount option redirects all umount requests to the
 174 /sbin/umount.<helper> independently on UID.
 175 .SH FILES
 176 .I /etc/mtab
 177 table of mounted file systems
 178 .SH ENVIRONMENT
 179 .IP LIBMOUNT_FSTAB=<path>
 180 overrides the default location of the fstab file
 181 .IP LIBMOUNT_MTAB=<path>
 182 overrides the default location of the mtab file
 183 .IP LIBMOUNT_DEBUG=0xffff
 184 enables debug output
 185 .SH "SEE ALSO"
 186 .BR umount (2),
 187 .BR mount (8),
 188 .BR losetup (8)
 189 .SH HISTORY
 190 A
 191 .B umount
 192 command appeared in Version 6 AT&T UNIX.
 193 .SH AVAILABILITY
 194 The umount command is part of the util-linux package and is available from
 195 .UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 196 Linux Kernel Archive
 197 .UE .