NAME
umount —
unmount file systems
SYNOPSIS
umount |
[-fNnv] special ... |
node ... | fsid ... |
umount |
-a | -A
[-F fstab]
[-fnv] [-h
host] [-t
type] |
DESCRIPTION
Theumount utility calls the
unmount(2) system call to remove a file system from the file system
tree. The file system can be specified by its special
device or remote node (rhost:path), the path to the mount point
node or by the file system ID fsid
as reported by “mount -v” when run by root.
The options are as follows:
-a- All the file systems described in fstab(5) are unmounted.
-A- All the currently mounted file systems except the root are unmounted.
-Ffstab- Specify the fstab file to use.
-f- 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
umountwithout the-fflag is hung on an NFS mount point, use the-Nflag instead. Also, doing a forced dismount of an NFSv3 mount when rpc.lockd(8) is running is unsafe and can result in a crash. -hhost- Only file systems mounted from the specified host will be unmounted. This
option implies the
-Aoption and, unless otherwise specified with the-toption, will only unmount NFS file systems. -N- Do a forced dismount of an NFS mount point without checking the mount
path. This option can only be used with the path to the mount point
node 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 NFS server while holding a vnode lock on the
mounted-on vnode, such that
umountwith the-fflag can't complete. Using this option can result in a loss of file updates that have not been flushed to the NFS server. -n- Unless the
-fis used, theumountwill 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. -ttype- 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
“no” to specify the file system types for which action
should not
be taken. For example, the
umountcommand:umount -a -t nfs,nullfs
unmounts all file systems of the type NFS and NULLFS that are listed in the fstab(5) file.
-v- Verbose, additional information is printed out as each file system is unmounted.
ENVIRONMENT
PATH_FSTAB- If the environment variable
PATH_FSTABis set, all operations are performed against the specified file.PATH_FSTABwill not be honored if the process environment or memory address space is considered “tainted”. (See issetugid(2) for more information.)
FILES
- /etc/fstab
- file system table
SEE ALSO
HISTORY
A umount utility appeared in
Version 1 AT&T UNIX.