I think of such virtualization as "rolling back by rolling forward". I can just deploy whatever version I want, when I want. If I don't like what's there, I can

I think of such virtualization as "rolling back by rolling forward". I can just deploy whatever version I want, when I want. If I don't like what's there, I can deploy a different version that happens to be an earlier version. Docker by itself isn't enough. But Docker in concert with Kubernetes (or Openshift, in my world) is very, very powerful.