I presented the thinking and summary of this at PyCon AU. Here is a recording of the talk -- https://youtu.be/I326bpbdvJo - (tonybaloney)
There's also Bocker, a minimalistic Docker implementation in 100 lines of bash¹.
I'd prefer Rocker, a Docker written in Rust :)
"Damn the fools, Docker is so much more than cgroups and chroot! [I just reimplemented the rest in two days]."
This is great, and the code is particularly easy to follow and quite Pythonic. Nice!