diff --git a/configuration.nix b/configuration.nix
index ddafa53..d605f9a 100755
--- a/configuration.nix
+++ b/configuration.nix
@@ -114,13 +114,20 @@
   services.openssh.enable = true;
   services.openssh.settings.PasswordAuthentication = false;
 
-  networking.firewall.enable = true;
   # Open ports in the firewall.
+  networking.firewall.enable = true;
   networking.firewall.allowedTCPPorts = [ 
     1972 # SSH
   ];
   # networking.firewall.allowedUDPPorts = [ ... ];
 
+  # Garbage collection to remove old NixOs iterations
+  nix.gc = {
+    automatic = true;
+    dates = "weekly";
+    options = "--delete-older-than 30d";
+  };
+
   # Copy the NixOS configuration file and link it from the resulting system
   # (/run/current-system/configuration.nix). This is useful in case you
   # accidentally delete configuration.nix.