diff --git a/nixos/configuration.nix b/nixos/configuration.nix
index 3087a8a..c17697c 100644
--- a/nixos/configuration.nix
+++ b/nixos/configuration.nix
@@ -12,7 +12,7 @@
 	];
 
 	system.stateVersion = "21.05";
-	system.autoUpgrade.channel = "//nixos.org/channels/nixos-unstable";
+	system.autoUpgrade.channel = "https://nixos.org/channels/nixos-unstable";
 
 	# boot
 	boot.zfs.requestEncryptionCredentials = []; # list -> default: true - always request for password
diff --git a/nixos/default.nix b/nixos/default.nix
index 1ac4d6b..40a2b2a 100644
--- a/nixos/default.nix
+++ b/nixos/default.nix
@@ -6,8 +6,11 @@
 
 {
 	system.autoUpgrade.enable = true;
+	nix.optimise.automatic = true;
+	nix.gc.automatic = true;
 
 	networking.useDHCP = false;
+	networking.firewall.enable = true; # is already enabled ...
 
 	services.openssh = {
 		enable = true;