Using mdns-publisher to hack together mDNS subdomains


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, ...}:

	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; [

	environment.systemPackages = with pkgs; [
		# 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 = [

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

sudo mdns-publish-cname
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?