The containers can share a file system layer which is mounted read only. Without write access the containers can't interfere with each other and there only nee

The containers can share a file system layer which is mounted read only. Without write access the containers can't interfere with each other and there only needs to be one copy of these shared files on the host. With something like AUFS (like what docker does) a R/W layer can be placed on top of this allowing the guest container to modify its own files without impacting the underlying shared read only layer.