To answer this more explicitly than the other comment: Yes, CoreOS is intended as the host system for containers. Inside the Docker (or rkt) containers you can

To answer this more explicitly than the other comment: Yes, CoreOS is intended as the host system for containers. Inside the Docker (or rkt) containers you can run whichever distribution or static binary you like. The combination of CoreOS+Kubernetes+Docker+Alpine Linux (inside the containers) works pretty well in my experience.