umount.nfs and umount.nfs4 are a part of nfs(5) utilities package,
which provides NFS client functionality.
umount.nfs4 and umount.nfs are meant to be used by the umount(8)
command for unmounting NFS shares. This subcommand, however, can also
be used as a standalone command with limited functionality.
dir is the directory on which the file system is mounted.
-f Force unmount the file system in case of unreachable NFS
-v Be verbose.
-n Do not update /etc/mtab. By default, an entry is created in
/etc/mtab for every mounted file system. Use this option to
skip deleting an entry.
-r In case unmounting fails, try to mount read-only.
-l Lazy unmount. Detach the file system from the file system
hierarchy now, and cleanup all references to the file system
as soon as it is not busy anymore.
-h Print help message.