add common config

common/default.nix

@@ -0,0 +1,47 @@
+# Common/default.nix
+
+# Inputs for this module, we don't use anything so can be empty.
+{ ... }:
+
+{
+  imports = [
+    # User account definitions
+    ./users
+    ./services
+  ];
+
+  # Clean /tmp on boot.
+  boot.cleanTmpDir = true;
+
+  # Set your time zone.
+  time.timeZone = "Europe/Amsterdam";
+
+  # Nix Settings
+  nix = {
+    package = pkgs.nixUnstable;
+    autoOptimiseStore = true;
+    binaryCaches = [
+      "https://cachix.cachix.org"
+      "https://nix-community.cachix.org"
+      "https://nixpkgs-review-bot.cachix.org"
+    ];
+    binaryCachePublicKeys = [
+      "cachix.cachix.org-1:eWNHQldwUO7G2VkjpnjDbWwy4KQ/HNxht7H4SSoMckM="
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      "nixpkgs-review-bot.cachix.org-1:eppgiDjPk7Hkzzz7XlUesk3rcEHqNDozGOrcLc8IqwE="
+    ];
+    trustedUsers = [ "root" "victor" ];
+    extraOptions = ''
+      experimental-features = nix-command flakes
+    '';
+  };
+
+  nixpkgs.config.allowUnfree = true;
+
+  # Limit the systemd journal to 100 MB of disk or the
+  # last 7 days of logs, whichever happens first.
+  services.journald.extraConfig = ''
+    SystemMaxUse=100M
+    MaxFileSec=7day
+  '';
+}