UMOUNT(8) System Administration UMOUNT(8)

NAMEumount − unmount file systems

SYNOPSISumount [−hV]

umount −a [−dflnrv ] [−t vfstype] [−O options]umount [−dflnrv ] { dir |device}...

DESCRIPTIONTheumount command detaches the file system(s) mentioned from the file hierarchy. A file system is spec-ified by giving the directory where it has been mounted. Giving the special device on which the file systemlives may also work, but is obsolete, mainly because it will fail in case this device was mounted on morethan one directory.

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 offendingprocess could even be umount itself - it opens libc, and libc in its turn may open for example locale files.A lazy unmount avoids this problem.

Options for theumount command:

−V Print version and exit.

−h Print help message and exit.

−v Verbose mode.

−n Unmount without writing in/etc/mtab.

−r In case unmounting fails, try to remount read-only.

−d In case the unmounted device was a loop device, also free this loop device.

−i Don’t call the /sbin/umount.<filesystem> helper even if i t exists. By default /sbin/umount.<filesys-tem> helper is called if one exists.

−a All of the file systems described in/etc/mtabare unmounted. (With umount version 2.7 and later:the proc filesystem is not unmounted.)

−t vfstypeIndicate that the actions should only be taken on file systems of the specified type. More than onetype may be specified in a comma separated list. The list of file system types can be prefixed withno to specify the file system types on which no action should be taken.

−O optionsIndicate that the actions should only be taken on file systems with the specified options in/etc/fstab. More than one option type may be specified in a comma separated list. Each optioncan be prefixed withno to specify options for which no action should be taken.

−f Force unmount (in case of an unreachable NFS system). (Requires kernel 2.1.116 or later.)

−l Lazy unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup all refer-ences to the filesystem as soon as it is not busy anymore. (Requireskernel 2.4.11 or later.)

−−no−canonicalizeDon’t canonicalize paths. For more details about this option see themount(8) man page.

−−fake Causes everything to be done except for the actual system call; this ‘‘fakes’’ unmounting thefilesystem. It can beused to remove entries from /etc/mtabthat were unmounted earlier with the-n option.

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UMOUNT(8) System Administration UMOUNT(8)

THE LOOP DEVICEThe umount command will free the loop device (if any) associated with the mount, in case it finds theoption ‘loop=...’ i n /etc/mtab, or when the −d option was given. Any pending loop devices can be freedusing ‘losetup -d’, seelosetup(8).

NOTESThe syntax of external umount helpers is:

/sbin/umount.<suffix> { dir |device} [ −nlfvr ] [−t type.subtype]

where the <suffix> is filesystem type or a value from "uhelper=" or "helper=" mtab option. The −t option isused forfilesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).

The uhelper= (unprivileged umount helper) is possible to use when non-root user wants to umount a mount-point which is not defined in the /etc/fstab file (e.g devices mounted by udisk).

The helper= mount option redirects all umount requests to the /sbin/umount.<helper> independently onUID.

FILES/etc/mtabtable of mounted file systems

SEE ALSOumount(2), mount(8), losetup(8).

HISTORYA umount command appeared in Version 6 AT&T UNIX.

AV A ILABILITYThe umount command is part of the util-linux package and is available from ftp://ftp.ker-nel.org/pub/linux/utils/util-linux/.

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