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UMOUNT(8) System Manager's Manual UMOUNT(8)

umountunmount filesystems

umount [-fvFR] [-t fstypelist] special | node

umount -a [-fvF] [-h host] [-t fstypelist]

The umount command calls the unmount(2) system call to remove a special device or the remote node (rhost:path) from the filesystem tree at the point node. If either special or node are not provided, the appropriate information is taken from the fstab(5) file.

The options are as follows:

All the currently mounted filesystems except the root are unmounted.
The filesystem is forcibly unmounted. Active special devices continue to work, but all other files return errors if further accesses are attempted. The root filesystem cannot be forcibly unmounted.
Fake the unmount; perform all other processing but do not actually attempt the unmount. (This is most useful in conjunction with -v, to see what umount would attempt to do).
Take the special | node argument as a path to be passed directly to unmount(2), bypassing all attempts to be smart about mechanically determining the correct path from the argument. This option is incompatible with any option that potentially unmounts more than one filesystem, such as -a, but it can be used with -f and/or -v. This is the only way to unmount something that does not appear as a directory (such as a nullfs mount of a plain file); there are probably other cases where it is necessary.
host
Only filesystems mounted from the specified host will be unmounted. This option is implies the -a option and, unless otherwise specified with the -t option, will only unmount NFS filesystems.
fstypelist
Is used to indicate the actions should only be taken on filesystems of the specified type. More than one type may be specified in a comma separated list. The list of filesystem types can be prefixed with “no” to specify the filesystem types for which action should not be taken. For example, the umount command:
umount -a -t nfs,mfs
    

unmounts all filesystems of the type NFS and MFS, whereas the umount command:

umount -a -t nonfs,mfs
    

unmounts all file systems except those of type NFS and MFS.

Verbose, additional information is printed out as each filesystem is unmounted.

/etc/fstab
filesystem table

unmount(2), fstab(5), mount(8)

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

May 17, 2009 NetBSD-7.0.1