[moshmosh]

Docker on Linux runs in a VM? No.

Systemd docker-replacement on a non-systemd Linux would need to run in a VM, though.

Systemd-docker-replacement: works only on systemd-Linux. Tooling for any other arrangement, including non-systemd linux, left as an exercise to the user.

Docker: works on Linux—systemd or otherwise. Has tooling to making working on macOS or Windows non-terrible and lets you use (mostly) the same commands as you would on Linux.

I'm saying that cross-platform tooling is what makes Docker Docker. Systemd can't replace it without replacing the tooling, even if it can do the same thing only on systemd-Linux.

[vially]

> Systemd docker-replacement on a non-systemd Linux would need to run in a VM, though.

Would it? There's no reason this hypothetical systemd-docker-replacement couldn't be architected in a way that would not have a runtime dependency on systemd-the-init-system.

In any case, I'm not even sure if systemd wants to be a docker replacement (although it does seem to pick up more and more container features lately). But there's definitely some overlap between the two projects (in particular around process/service management) but podman is a much more direct competitor to docker than systemd.