feat(lowmem): add swap and trusted users

global/lowmem/default.nix

@@ -0,0 +1,25 @@
+{ pkgs
+, lib
+, config
+, ... }: with lib; let
+  cfg = config.global.lowmem;
+in {
+  options.global.lowmem = {
+    enable = mkEnableOption "low memory optimisations";
+    swapsize = mkOption {
+      type = with types; int;
+      default = 8 * 1024;
+      description = "automatic swap file size";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    # enables remote nixos-rebuild
+    nix.settings.trusted-users = [ "koishi" ];
+
+    swapDevices = [ {
+      device = "/nix/persist/secret/swap";
+      size = cfg.swapsize;
+    } ];
+  };
+}