Kubernetes uses Docker (or now rkt) to do the actual containing. The focus is on scheduling and managing lots of containers. You may run O(10) containers on a

Kubernetes uses Docker (or now rkt) to do the actual containing. The focus is on scheduling and managing lots of containers. You may run O(10) containers on a single machine. When you run O(10k)+ containers in a cluster you need new tools to manage things.