Post Syndicated from original https://lwn.net/Articles/927491/

As a general rule, the purpose behind mounting a filesystem is to make that
filesystem’s contents visible to the system, or at least to the mount
namespace where that mount occurs. For similar reasons, it is unusual to
mount one filesystem on top of another, since that would cause the contents
of the over-mounted filesystem to be hidden. There are exceptions to
everything, though, and that extends to mounted filesystems; a
“tucking” mechanism proposed by Christian Brauner is designed to hide
mounted filesystems underneath other mounts — temporarily, at least.