The umount command detaches the file system(s) mentioned from the file hierarchy. A file system is specified by giving the directory where it has been mounted.
Print version and exit.
Verbose mode.
Unmount without writing in /etc/mtab.
In case unmounting fails, try to remount read-only.
All of the file systems described in /etc/mtab are unmounted except for the proc filesystem.
Indicate that 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 on which no action should be taken.
Force unmount (in case of an unreachable NFS system).