OpenVZ, user-mode Linux, and others were very widespread with web hosting and VPS providers since mid-/early-2000s (and probably a little earlier than that too)

OpenVZ, user-mode Linux, and others were very widespread with web hosting and VPS providers since mid-/early-2000s (and probably a little earlier than that too). Docker didn't invent containers, but they were a first mover (as far as I know) in the current flavor of "PaaS" or hosted "non-frameworks" (i.e. environments that don't force you into the hosting provider's userland choices such as library versions, etc.). It's easy to dismiss it as a better mousetrap, but it was an inflection point in the same way puppet and cfengine before it were inflection points in configuration management and "infrastructure as code"... Still, I find the Docker daemon massively invasive and too much of a potential gaping security hole. I wish it was more modular and less of it ran privileged/as root, and don't run it on anything sensitive as a result. Usually properly configuring a box and relying on existing process and other forms of isolation (including namespaces) is good enough, especially with good package management. Great for UX/workflow tooling in a dev VM though!