nixos/spec/channel.nix

{ inputs, ... }:
with inputs;
with nixpkgs.lib;
let
  mapInputs = fn: map fn (lists.remove "self" (attrNames inputs));
  channelPath = "/etc/nix/channels";
in
{
  nix = {
    nixPath = mapInputs (i: "${i}=${channelPath}/${i}");
    registry = listToAttrs (
      mapInputs (name: {
        inherit name;
        value = {
          flake = inputs.${name};
        };
      })
    );
  };

  systemd.tmpfiles.rules = mapInputs (i: "L+ ${channelPath}/${i}     - - - - ${inputs.${i}.outPath}");
}