Overlayfs, aufs, etc. are really irrelevant to containers.  They are used in Docker because it&#x27;s built around opaque binary disk images that do not compose, which I believe is a big flaw, but it doesn&#x27;t have to be this way.  For example, GNU Guix has a container implementation that does not use disk images at all but still achieves system-wide deduplication of software across all containers running on the host via simple bind mounts.