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  48 also work, but is obsolete, mainly because it will fail in case this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\-c\fR, \fB\-\-no\-canonicalize\fR
  70 Do not canonicalize paths.  For more details about this option see the
  71 .BR mount (8)
  72 man page.
  73 .TP
  74 \fB\-d\fR, \fB\-\-detach\-loop\fR
  75 In case the unmounted device was a loop device, also free this loop
  76 device.
  77 .TP
  78 \fB\-\-fake\fP
  79 Causes everything to be done except for the actual system call; this 'fakes'
  80 unmounting the filesystem.  It can be used to remove entries from
  81 .I /etc/mtab
  82 that were unmounted earlier with the
  83 .B \-n
  84 option.
  85 .TP
  86 \fB\-f\fR, \fB\-\-force\fR
  87 Force unmount (in case of an unreachable NFS system).  (Requires kernel
  88 2.1.116 or later.)
  89 .TP
  90 \fB\-i\fR, \fB\-\-internal\-only\fR
  91 Do not call the /sbin/umount.<filesystem> helper even if it exists.  By
  92 default /sbin/umount.<filesystem> helper is called if one exists.
  93 .TP
  94 \fB\-n\fR, \fB\-\-no\-mtab\fR
  95 Unmount without writing in
  96 .IR /etc/mtab .
  97 .TP
  98 \fB\-l\fR, \fB\-\-lazy\fR
  99 Lazy unmount.  Detach the filesystem from the filesystem hierarchy now,
 100 and cleanup all references to the filesystem as soon as it is not busy
 101 anymore.  (Requires kernel 2.4.11 or later.)
 102 .TP
 103 \fB\-O\fR, \fB\-\-test\-opts\fR \fIoptions,list\fR
 104 Indicate that the actions should only be taken on file systems with the
 105 specified options in
 106 .IR /etc/fstab .
 107 More than one option type may be specified in a comma separated list.
 108 Each option can be prefixed with
 109 .B no
 110 to specify options for which no action should be taken.
 111 .TP
 112 \fB\-r\fR, \fB\-\-read\-only\fR
 113 In case unmounting fails, try to remount read-only.
 114 .TP
 115 \fB\-t\fR, \fB\-\-types\fR \fIvfstype,ext2,ext3\fR
 116 Indicate that the actions should only be taken on file systems of the
 117 specified
 118 .IR type .
 119 More than one type may be specified in a comma separated list.  The list
 120 of file system types can be prefixed with
 121 .B no
 122 to specify the file system types on which no action should be taken.
 123 .TP
 124 \fB\-v\fR, \fB\-\-verbose\fR
 125 Verbose mode.
 126 .TP
 127 \fB\-h\fR, \fB\-\-help\fR
 128 Print help message and exit.
 129 .TP
 130 \fB\-V\fR, \fB\-\-version\fR
 131 Print version and exit.
 132 .SH "THE LOOP DEVICE"
 133 The
 134 .B umount
 135 command will free the loop device (if any) associated with the mount, in
 136 case it finds the option 'loop=...' in
 137 .IR /etc/mtab ,
 138 or when the \-d option was given.  Any pending loop devices can be freed
 139 using 'losetup -d', see
 140 .BR losetup (8).
 141 .SH NOTES
 142 The syntax of external umount helpers is:
 143 .PP
 144 .BI /sbin/umount. <suffix>
 145 .RI { dir | device }
 146 .RB [ \-nlfvr ]
 147 .RB [ \-t
 148 .IR type.subtype ]
 149 .PP
 150 where the <suffix> is filesystem type or a value from "uhelper=" or
 151 "helper=" mtab option.  The \-t option is used for filesystems with
 152 subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).
 153 .PP
 154 The uhelper= (unprivileged umount helper) is possible to use when
 155 non-root user wants to umount a mountpoint which is not defined in the
 156 /etc/fstab file (e.g. devices mounted by udisk).
 157 .PP
 158 The helper= mount option redirects all umount requests to the
 159 /sbin/umount.<helper> independently on UID.
 160 .SH FILES
 161 .I /etc/mtab
 162 table of mounted file systems
 163 .SH ENVIRONMENT
 164 .IP LIBMOUNT_FSTAB=<path>
 165 overrides the default location of the fstab file
 166 .IP LIBMOUNT_MTAB=<path>
 167 overrides the default location of the mtab file
 168 .IP LIBMOUNT_DEBUG=0xffff
 169 enables debug output
 170 .SH "SEE ALSO"
 171 .BR umount (2),
 172 .BR mount (8),
 173 .BR losetup (8)
 174 .SH HISTORY
 175 A
 176 .B umount
 177 command appeared in Version 6 AT&T UNIX.
 178 .SH AVAILABILITY
 179 The umount command is part of the util-linux package and is available from
 180 .UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 181 Linux Kernel Archive
 182 .UE .