Since  Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides ability to
       create mirrors of that mount such that mounts and umounts within any of the mirrors propagate to the other mirror. A slave mount receives propa-
       gation  from its master, but any not vice-versa.  A private mount carries no propagation abilities.  A unbindable mount is a private mount which
       cannot cloned through a bind operation. Detailed semantics is documented in Documentation/sharedsubtree.txt file in the kernel source tree.
              mount --make-shared mountpoint
              mount --make-slave mountpoint
              mount --make-private mountpoint
              mount --make-unbindable mountpoint