The unshare command enables you to make a previously available file system unavailable for mounting by clients. When you unshare an NFS file system, access from clients with existing mounts is inhibited. The file system might still be mounted on the client but the files are not accessible. The unshare command deletes the share permanently unless the –t option is used to temporarily unshare the file system.
The following example unshares the file system /usr/src:
# unshare /usr/src