command detaches the file system(s) mentioned 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may also work, but is obsolete, mainly because it will fail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.
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
itself – it opens libc, and libc in its turn may open for example
A lazy unmount avoids this problem.
Options for the
are unmounted. (With
version 2.7 and later: the
filesystem is not unmounted.)
to specify the file system types on which no action should be taken.
More than one option type may be specified in a comma separated
list. Each option can be prefixed with
to specify options for which no action should be taken.
that were unmounted earlier with the -n option.
command will free the loop device (if any) associated
with the mount, in case it finds the option `loop=…’ in
or when the -d option was given.
Any pending loop devices can be freed using `losetup -d’, see
The syntax of external umount helpers is:
where the <suffix> is filesystem type or a value from "uhelper=" mtab option.
The -t option is used for filesystems with subtypes support (for example
/sbin/mount.fuse -t fuse.sshfs).
The uhelper (unprivileged umount helper) is possible to used when non-root user
wants to umount a mountpoint which is not defined in the /etc/fstab file (e.g
devices mounted by HAL).
table of mounted file systems
The umount command is part of the util-linux-ng package and is available from