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| .TH UMOUNT 8 "July 2014" "util-linux" "System Administration" |
| .SH NAME |
| umount \- unmount file systems |
| .SH SYNOPSIS |
| .B umount \-a |
| .RB [ \-dflnrv ] |
| .RB [ \-t |
| .IR fstype ] |
| .RB [ \-O |
| .IR option ...] |
| .sp |
| .B umount |
| .RB [ \-dflnrv ] |
| .RI { directory | device }... |
| .sp |
| .B umount |
| .BR \-h | \-V |
| |
| .SH DESCRIPTION |
| The |
| .B umount |
| command detaches the mentioned file system(s) from the file hierarchy. A |
| file system is specified by giving the directory where it has been |
| mounted. Giving the special device on which the file system lives may |
| also work, but is obsolete, mainly because it will fail in case this |
| device was mounted on more than one directory. |
| .PP |
| Note that a file system cannot be unmounted when it is 'busy' - for |
| example, when there are open files on it, or when some process has its |
| working directory there, or when a swap file on it is in use. The |
| offending process could even be |
| .B umount |
| itself - it opens libc, and libc in its turn may open for example locale |
| files. A lazy unmount avoids this problem. |
| .SH OPTIONS |
| .TP |
| .BR \-a , " \-\-all" |
| All of the filesystems described in |
| .I /proc/self/mountinfo |
| (or in deprecated /etc/mtab) |
| are unmounted, except the proc, devfs, devpts, sysfs, rpc_pipefs and nfsd |
| filesystems. This list of the filesystems may be replaced by \fB\-\-types\fR |
| umount option. |
| .TP |
| .BR \-A , " \-\-all\-targets" |
| Unmount all mountpoints in the current namespace for the specified filesystem. |
| The filesystem can be specified by one of the mountpoints or the device name (or |
| UUID, etc.). When this option is used together with \fB\-\-recursive\fR, then |
| all nested mounts within the filesystem are recursively unmounted. |
| This option is only supported on systems where /etc/mtab is a symlink |
| to /proc/mounts. |
| .TP |
| .BR \-c , " \-\-no\-canonicalize" |
| Do not canonicalize paths. For more details about this option see the |
| .BR mount (8) |
| man page. Note that \fBumount\fR does not pass this option to the |
| .BI /sbin/umount. type |
| helpers. |
| .TP |
| .BR \-d , " \-\-detach\-loop" |
| When the unmounted device was a loop device, also free this loop |
| device. This option is unnecessary for devices initialized by |
| .BR mount (8), |
| in this case "autoclear" functionality is enabled by default. |
| .TP |
| .B \-\-fake |
| Causes everything to be done except for the actual system call or umount helper |
| execution; this 'fakes' unmounting the filesystem. It can be used to remove |
| entries from the deprecated |
| .I /etc/mtab |
| that were unmounted earlier with the |
| .B \-n |
| option. |
| .TP |
| .BR \-f , " \-\-force" |
| Force an unmount (in case of an unreachable NFS system). (Requires kernel |
| 2.1.116 or later.) |
| |
| Note that this option does not guarantee that umount command does not hang. |
| It's strongly recommended to use absolute paths without symlinks to avoid |
| unwanted readlink and stat system calls on unreachable NFS in umount. |
| .TP |
| .BR \-i , " \-\-internal\-only" |
| Do not call the \fB/sbin/umount.\fIfilesystem\fR helper even if it exists. |
| By default such a helper program is called if it exists. |
| .TP |
| .BR \-l , " \-\-lazy" |
| Lazy unmount. Detach the filesystem from the file hierarchy now, |
| and clean up all references to this filesystem as soon as it is not busy |
| anymore. (Requires kernel 2.4.11 or later.) |
| .TP |
| .BR \-n , " \-\-no\-mtab" |
| Unmount without writing in |
| .IR /etc/mtab . |
| .TP |
| .BR \-O , " \-\-test\-opts " \fIoption\fR... |
| Unmount only the filesystems that have the specified option set in |
| .IR /etc/fstab . |
| More than one option may be specified in a comma-separated list. |
| Each option can be prefixed with |
| .B no |
| to indicate that no action should be taken for this option. |
| .TP |
| .BR \-R , " \-\-recursive" |
| Recursively unmount each specified directory. Recursion for each directory will |
| stop if any unmount operation in the chain fails for any reason. The relationship |
| between mountpoints is determined by /proc/self/mountinfo entries. The filesystem |
| must be specified by mountpoint path; a recursive unmount by device name (or UUID) |
| is unsupported. |
| .TP |
| .BR \-r , " \-\-read\-only" |
| When an unmount fails, try to remount the filesystem read-only. |
| .TP |
| .BR \-t , " \-\-types " \fItype\fR... |
| Indicate that the actions should only be taken on filesystems of the |
| specified |
| .IR type . |
| More than one type may be specified in a comma-separated list. The list |
| of filesystem types can be prefixed with |
| .B no |
| to indicate that no action should be taken for all of the mentioned types. |
| .BR |
| Note that |
| .B umount |
| reads information about mounted filesystems from kernel (/proc/mounts) and |
| filesystem names may be different than filesystem names used in the /etc/fstab |
| (e.g. "nfs4" vs. "nfs"). |
| .TP |
| .BR \-v , " \-\-verbose" |
| Verbose mode. |
| .TP |
| .BR \-V , " \-\-version" |
| Display version information and exit. |
| .TP |
| .BR \-h , " \-\-help" |
| Display help text and exit. |
| .SH "LOOP DEVICE" |
| The |
| .B umount |
| command will automatically detach loop device previously initialized by |
| .BR mount (8) |
| command independently of /etc/mtab. |
| |
| In this case the device is initialized with "autoclear" flag (see |
| .BR losetup (8) |
| output for more details), otherwise it's necessary to use the option \fB \-\-detach\-loop\fR |
| or call \fBlosetup -d <device>\fR. The autoclear feature is supported since Linux 2.6.25. |
| .SH EXTERNAL HELPERS |
| The syntax of external unmount helpers is: |
| .PP |
| .RS |
| .BI umount. suffix |
| .RI { directory | device } |
| .RB [ \-flnrv ] |
| .RB [ \-t |
| .IR type . subtype ] |
| .RE |
| .PP |
| where \fIsuffix\fR is the filesystem type (or the value from a |
| \fBuhelper=\fR or \fBhelper=\fR marker in the mtab file). |
| The \fB\-t\fR option can be used for filesystems that |
| have subtype support. For example: |
| .PP |
| .RS |
| .B umount.fuse \-t fuse.sshfs |
| .RE |
| .PP |
| A \fBuhelper=\fIsomething\fR marker (unprivileged helper) can appear in |
| the \fI/etc/mtab\fR file when ordinary users need to be able to unmount |
| a mountpoint that is not defined in \fI/etc/fstab\fR |
| (for example for a device that was mounted by \fBudisks\fR(1)). |
| .PP |
| A \fBhelper=\fItype\fR marker in the mtab file will redirect |
| all unmount requests |
| to the \fB/sbin/umount.\fItype\fR helper independently of UID. |
| .PP |
| Note that \fI/etc/mtab\fR is currently deprecated and helper= and another |
| userspace mount options are maintained by libmount. |
| .SH FILES |
| .TP |
| .I /etc/mtab |
| table of mounted filesystems (deprecated and usually replaced by |
| symlink to /proc/mounts) |
| .TP |
| .I /etc/fstab |
| table of known filesystems |
| .TP |
| .I /proc/self/mountinfo |
| table of mounted filesystems generated by kernel. |
| .SH ENVIRONMENT |
| .IP LIBMOUNT_FSTAB=<path> |
| overrides the default location of the fstab file (ignored for suid) |
| .IP LIBMOUNT_MTAB=<path> |
| overrides the default location of the mtab file (ignored for suid) |
| .IP LIBMOUNT_DEBUG=all |
| enables libmount debug output |
| .SH "SEE ALSO" |
| .BR umount (2), |
| .BR losetup (8), |
| .BR mount (8) |
| .SH HISTORY |
| A |
| .B umount |
| command appeared in Version 6 AT&T UNIX. |
| .SH AVAILABILITY |
| The umount command is part of the util-linux package and is available from |
| .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/ |
| Linux Kernel Archive |
| .UE . |