Using mdns-publisher to hack together mDNS subdomains

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Howdy!

I’m an intermittent NixOS user, trying again to make it my daily driver. My ability to debug Nix is limited to repeatedly trying to run nixos-rebuild again and again until something works. Would love to hear tips and tricks other people are using as part of this discussion.

I have a home server with a couple of services exposed. I’ve set up avahi so that I can access my server at home via kitsault.local, but trying to remember all the ports for my various services is a drag! I want to have subdomains for each service, but the kicker is that this seems difficult to accomplish even without the Gates of Nix standing before us.

I started after finding this blog post: Painfully Obvious → Using mDNS aliases within your home network

This is where I discovered mdns-publish, a python package not currently nix-ified. So, to start, and with help from Python - NixOS Wiki, I set up a configuration.nix to look like this:

{ config, pkgs, ...}:

	let
	my-python-packages = ps: with ps; [
  # ...
  (
    buildPythonPackage rec {
			pname = "mdns-publisher";
			version = "0.9.2";
      src = fetchPypi {
        inherit pname version;
        sha256 = "sha256-sjCQKnsFR6w3IwCvZ1GDw0VqnLjEbO3ecgKOJrSZj84==";
      };
			doCheck = false;
			propagatedBuildInputs = with pythonPackages; [
				dbus-python
			];
		}
  )
];
in
{

	environment.systemPackages = with pkgs; [
		nssmdns
		avahi
		# mdns-publisher
		(pkgs.python3.withPackages my-python-packages)
	];

	services.avahi = {
		enable = true;
		publish = {
			enable = true;
			addresses = true;
			workstation = true;
		};
		nssmdns = true;
	};


}

I manage my machine states with a single flake.nix, without exposing a lot of unneeded detail, it looks like

{
  inputs.nixpkgs.url = github:NixOS/nixpkgs;

  outputs = { self, nixpkgs, ... }:
    {
      nixosConfigurations.kitsault = nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";
        modules = [
                  ./mdns-configuration.nix
                 ...
        ];
      };
    };
}

This has gotten me pretty close, I can run the command that mdns-publisher exposes but when I run

sudo mdns-publish-cname test.my-machine.local
sudo mdns-publish-cname test.local

I get

dbus.exceptions.DBusException: org.freedesktop.Avahi.NotPermittedError: Not permitted

And I’m unsure of how to continue - ChatGPT isn’t versed enough in Nix to help. Thoughts?