The foundation of the design for containers in the kernel is that there isn't one; there is no container abstraction that the kernel recognizes. Instead, the kernel provides a long list of components — namespaces, control groups, sandboxing mechanisms, and more — along with a note that says, in effect, "some assembly required". There have been attempts (repeatedly) over the years to turn containers into first-class objects with kernel support, but they have never gotten far. Now Josef Bacik is making a try with a concept that he calls "cells".