The pivot_root() operation is an essential step in virtualizing a
container's root directory. Current pivot_root() semantics require that a mountpoint is not a shared mountpoint. If it is, the pivot_root() operation will not be allowed. However, some containers need to have a virtualized root directory while at the same time have the root directory be a shared mountpoint. This is necessary when mounts between the host and the container are supposed to propagate in order to have a
straightforward mechanism to share mount information. In this talk we will explain the original reason for blocking pivot_root() on shared mountpoints and start a discussion centered around a patchset that is a necessary precondition to safely enable pivot_root() on shared mountpoints.