This post is mostly for myself: I find the Traefik documentation hard to navigate, so having figured this out in response to a question on Stack Overflow, I’m putting it here to help it stick in my head. The question asks essentially how to perform port-based routing of requests to containers, so that a request for http://example.com goes to one container while a request for http://example.com:9090 goes to a different container.

systemd-nspawn has been called “chroot on steroids”, but if you think of it as Docker with a slightly different target you wouldn’t be far wrong, either. It can be used to spawn containers on your host, and has a variety of options for configuring the containerized environment through the use of private networking, bind mounts, capability controls, and a variety of other facilities that give you flexible container management. There are many different ways in which it can be used.