It's useful if you want to bring up a containerized service, optionally update OS, run tests, and if everything is good, copy that instance a bunch of times rat

It's useful if you want to bring up a containerized service, optionally update OS, run tests, and if everything is good, copy that instance a bunch of times rather than starting fresh. It gets you scale out a batch of VMs remarkably quickly, while leaving the original available for os/patch updates. If I'm willing to pay the cost of keeping an idle VM around, subsequent launches are probably an order of magnitude faster than docker hello-world.