Regarding d, this decision with Docker to use a daemon to control your processes (that is not init) continues to baffle me. It seems on the surface of it to be a really naive way to schedule your cgroups, but you could just as easily do it with a wrapper that terminates. Or just swallow that pill and go with systemd already.

I haven't seen any other container like system on Linux with that design. And I haven't seen it go zombie on me, but I have had it die on me for reasons I have never fully understood. There are bugs in there, just like with any young project of course. It's possible to recover from that state with intimate understanding of how Docker works, but it wreaks havoc on higher lever tools.