Talking about containers: is there an easy way to run “system” containers? This is, containers that run systemd and everything else you would expect to be running on a normal Linux OS. I rely heavily on VMs to simulate cloud environments, but I would love to use lightweight containers instead. Also, these “system” containers should be able to run containers inside them as well (docker in docker?).

I saw something on github the other day that may work (can’t remember the name, something about “box”), but it wasn’t available for Macos.

You are probably referring to Sysbox (https://github.com/nestybox/sysbox), which I believe will meet your requirements (systemd, inner containers, security, etc).

Btw, Sysbox is already supported in Docker-Desktop (business tier only), so you can easily do what you want with this instruction:

$ docker run -it --rm -e SYSBOX_SYSCONT_MODE=TRUE ghcr.io/nestybox/ubuntu-focal-systemd-docker:latest bash

Disclaimer: I'm Sysbox's co-creator and currently working for Docker.