umount(8) - Manual pages

SYNOPSIS

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

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

The umount command calls the unmount(2) system call (or an external unmount program) 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.

By default, the file system type is extracted from the kernel and used to choose an external unmount program, whose name is formed by appending an underscore and the type string to “umount”. This matches the form used by the external mount programs used by mount(8). If this program is found on the path, it is used in preference to calling unmount(2) directly. Note that in the NetBSD base system no such external unmount programs exist; the facility is provided in the hopes that it will be useful for third party file systems and/or for research.

The options are as follows:

-a

All the currently mounted filesystems except the root are unmounted.

-f

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.

-F

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).

-R

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. This option also disables the use of any external unmount program.

-h 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.

-t 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: