add guix. also comment about dvd rule

configuration.nix

@@ -106,6 +106,8 @@ openssl
 openssl.dev
 openssl.out
 sbcl
+
+guix
     # cmake
     # harfbuzz
     # freetype
@@ -131,6 +133,7 @@ sbcl
     # glibc
     # gobject-introspection
   ];
+  # for Apple Super Driver - usb dvd player
   services.udev.extraRules = ''
     ACTION=="add", ATTRS{idProduct}=="1500", ATTRS{idVendor}=="05ac", DRIVERS=="usb", RUN+="${pkgs.sg3_utils}/bin/sg_raw /dev/$kernel EA 00 00 00 00 00 01"
   '';
@@ -150,6 +153,7 @@ sbcl
 
   # Enable the OpenSSH daemon.
   services.openssh.enable = true;
+  services.guix.enable = true;
 
   # Open ports in the firewall.
   # networking.firewall.allowedTCPPorts = [ ... ];