anchor.diff:  
       users.extraGroups.messagebus.gid = config.ids.gids.messagebus;
   
  -    # FIXME: these are copied verbatim from the dbus source tree.  We
  -    # should install and use the originals.
  -    systemd.units."dbus.socket".text =
  -      ''
  -        [Unit]
  -        Description=D-Bus System Message Bus Socket
  -
  -        [Socket]
  -        ListenStream=/var/run/dbus/system_bus_socket
  -      '';
  -
  -    systemd.units."dbus.service".text =
  -      ''
  -        [Unit]
  -        Description=D-Bus System Message Bus
  -        Requires=dbus.socket
  -
  -        [Service]
  -        ExecStartPre=${pkgs.dbus_tools}/bin/dbus-uuidgen --ensure
  -        ExecStartPre=-${pkgs.coreutils}/bin/rm -f /var/run/dbus/pid
  -        ExecStart=${pkgs.dbus_daemon}/bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation
  -        ExecReload=${pkgs.dbus_tools}/bin/dbus-send --print-reply --system --type=method_call --dest=org.freedesktop.DBus / org.freedesktop.DBus.ReloadConfig
  -        OOMScoreAdjust=-900
  -      '';
  +    systemd.packages = [ pkgs.dbus.daemon ];
   
       security.setuidOwners = singleton
         { program = "dbus-daemon-launch-helper";
  
positive.code:     buildCommand = ''
        ensureDir $out
  
        cp -v ${pkgs.dbus_daemon}/etc/dbus-1/system.conf $out/system.conf
  
        # !!! Hm, these `sed' calls are rather error-prone...
  
  
negative.code: 
    config = mkIf cfg.enable {
  
      environment.systemPackages = [ pkgs.dbus.daemon pkgs.dbus_tools ];
  
      environment.etc = singleton
        { source = configDir;
  