anchor.diff:  
       environment.systemPackages = [ alsaUtils ];
   
  -    environment.etc = [ { source = config.sound.extraConfig;
  -                          target = configPath;
  -                        }
  -                      ];
  +    environment.etc = mkIf (config.sound.extraConfig != "")
  +      [
  +        { source = pkgs.writeText "asound.conf" config.sound.extraConfig;
  +          target = "asound.conf";
  +        }
  +      ];
   
       # ALSA provides a udev rule for restoring volume settings.
       services.udev.packages = [ alsaUtils ];
  
positive.code: let
  
    inherit (pkgs) alsaUtils;
  
    soundState = "/var/lib/alsa/asound.state";
  
    configPath = "asound.conf";
  
  in
  
  
negative.code: 
        extraConfig = mkOption {
          type = types.lines;
          default = "";
          example = ''
            defaults.pcm.!card 3
          '';
  