create custom module system

modules/agenix.nix

@@ -0,0 +1,10 @@
+{ config, ... }: {
+  age = {
+    identityPaths = [ "/root/age_ed25519" ];
+
+    secrets = {
+      "host_ed25519".file = config.custom.ssh.hostKey;
+      "user_ed25519".file = config.custom.ssh.userKey;
+    };
+  };
+}

modules/custom.nix

@@ -0,0 +1,50 @@
+{ lib, config, ... }: {
+  options = {
+    custom = {
+      dataDisk.enable = lib.mkOption {
+        default = false;
+        type = lib.types.bool;
+        description = ''
+          Whether to automatically mount /dev/sda1 on /mnt/data
+        '';
+      };
+
+      ssh = {
+        hostCert = lib.mkOption {
+          type = lib.types.str;
+          description = ''
+            SSH host certificate
+          '';
+        };
+
+        userCert = lib.mkOption {
+          type = lib.types.str;
+          description = ''
+            SSH user certificate
+          '';
+        };
+
+        hostKey = lib.mkOption {
+          default = ../secrets/${config.networking.hostName}_host_ed25519.age;
+          type = lib.types.path;
+          description = ''
+            SSH host key
+          '';
+        };
+
+        userKey = lib.mkOption {
+          default = ../secrets/${config.networking.hostName}_user_ed25519.age;
+          type = lib.types.path;
+          description = ''
+            SSH user key
+          '';
+        };
+      };
+    };
+  };
+
+  config = {
+    fileSystems."/dev/data" =
+      lib.mkIf config.custom.dataDisk.enable { device = "/dev/sda1"; };
+  };
+}

modules/disk-config.nix

@@ -0,0 +1,34 @@
+{
+  disko.devices = {
+    disk = {
+      vdb = {
+        device = "/dev/nvme0n1";
+        type = "disk";
+        content = {
+          type = "gpt";
+          partitions = {
+            ESP = {
+              type = "EF00";
+              size = "500M";
+              content = {
+                type = "filesystem";
+                format = "vfat";
+                mountpoint = "/boot";
+              };
+            };
+            root = {
+              end = "-4G";
+              content = {
+                type = "filesystem";
+                format = "btrfs";
+                mountpoint = "/";
+              };
+            };
+            swap = { size = "100%"; };
+          };
+        };
+      };
+    };
+  };
+}
+