utility calls the
system call to remove a file system from the file system tree.
The file system can be specified by its
device or remote node
the path to the mount point
or by the file system ID
as reported by
when run by root.
The options are as follows:
All the file systems described in
All the currently mounted file systems are unmounted,
except for those mounted at
| -F fstab
file to use.
The file system is forcibly unmounted.
Active special devices continue to work,
but all other files return errors if further accesses are attempted.
The root file system cannot be forcibly unmounted.
For NFS, a forced dismount can take up to 1 minute or more to
complete against an unresponsive server and may throw away
data not yet written to the server for this case.
If a process, such as
flag is hung on an
mount point, use the
Also, doing a forced dismount of an NFSv3 mount when
is running is unsafe and can result in a crash.
| -h host
Only file systems mounted from the specified host will be
This option implies the
option and, unless otherwise specified with the
option, will only unmount
Do a forced dismount of an
mount point without checking the mount path.
This option can only be used with the path to the mount point
and the path must be specified exactly as it was at mount time.
This option is useful when a process is hung waiting for an unresponsive
server while holding a vnode lock on the mounted-on vnode, such that
flag can't complete.
Using this option can result in a loss of file updates that have not been
flushed to the
is used, the
will not unmount an active file system.
It will, however, perform a flush.
This flag disables this behaviour, preventing the flush
if there are any files open.
| -t type
Is used to indicate the actions should only be taken on
file systems of the specified type.
More than one type may be specified in a comma separated list.
The list of file system types can be prefixed with
to specify the file system types for which action should
For example, the
umount -a -t nfs,nullfs
unmounts all file systems of the type
that are listed in the
Verbose, additional information is printed out as each file system