The atomic hosts from CentOS and Fedora earn their
atomic namesake by providing for atomic, image-based system updates via rpm-ostree, and atomic, image-based application updates via docker containers.
application division isn’t set in stone, however. There’s room for system components to move across from the somewhat rigid world of ostree commits to the freer-flowing container side.
In particular, the key atomic host components involved in orchestrating containers across multiple hosts, such as flannel, etcd and kubernetes, could run instead in containers, making life simpler for those looking to test out newer or different versions of these components, or to swap them out for alternatives.
The devel tree of CentOS Atomic Host, which features a trimmed-down system image that leaves out kubernetes and related system components, is a great place to experiment with alternative methods of running these components, and swapping between them.