nix-processmgmt VS NixOS-docker

I somewhere saw this project being mentioned: https://github.com/svanderburg/nix-processmgmt

That's nice and it showcases how Nix can create a declarative process management atop a script-based imperative manager. How is your experience with it? Also note that there's https://github.com/svanderburg/nix-processmgmt, a manager agnostic processes management framework supporting s6 among others, but your way seems a bit more straightforward.

There's a project still being developed: https://github.com/svanderburg/nix-processmgmt my understanding is that if home-manager would use it (I don't know if there is even plan to do that, it's not the same author), it would be able to work without needing systemd.

(builtins.fetchTarball "https://github.com/svanderburg/nix-processmgmt/archive/6def8584c6b028c922c550859a07b989d21d6f73.tar.gz")

It's not really clear to me what you are asking. Are you maybe looking for nix-processmgmt? (NixCon 2020 talk: https://cfp.nixcon.org/nixcon2020/talk/TW79FU/)

Luckily, I did not have to start from scratch as Nix serves their own docker image. I mounted one of my directories and was able to drop into a Nix shell with my configuration file.

There is one: https://github.com/NixOS/docker

But it's more of a Nix docker image than a NixOS one, because half of the things that NixOS gives you don't really make much sense in a docker image (systemd in a container?).

I only know of the nix package manager. https://hub.docker.com/r/nixos/nix

Ability to run buildkite agents inside a kubernetes cluster on preemble instances without need to modify agent’s Dockerfile every time new dependency comes up - was one of major reasons to learn Nix. I’m just using nixos/docker image as a base, install buildkite-agent and some base stuff like bash via nix-env inside Dickerfile, everything else lays in flake.nix of every project my dockerized nixified buildkite agent run.