This command enables you to remove a remote file system that is currently mounted. The umount command supports the -V option to allow for testing. You might also use the -a option to unmount several file systems at one time. If mount-points are included with the -a option, those file systems are unmounted. If no mount points are included, an attempt is made to unmount all file systems that are listed in /etc/mnttab except for the “required” file systems, such as /, /usr, /var, /proc, /dev/fd, and /tmp. Because the file system is already mounted and should have an entry in /etc/mnttab, you do not need to include a flag for the file-system type.
The -f option forces a busy file system to be unmounted. You can use this option to unhang a client that is hung while trying to mount an unmountable file system.
By forcing an unmount of a file system, you can cause data loss if files are being written to.
See the following examples.
# umount /usr/man
This example displays the results of running umount -a -V:
# umount -a -V umount /home/kathys umount /opt umount /home umount /net
Notice that this command does not actually unmount the file systems.