clanCore: init machine_id.nix with clan.core.machine.{id,diskId}

clanModules/single-disk/default.nix

@@ -1,4 +1,7 @@
 { lib, config, ... }:
+let
+  cfg = config.clan.single-disk;
+in
 {
   options.clan.single-disk = {
     device = lib.mkOption {
@@ -8,26 +11,38 @@
       # Question: should we set a default here?
       # default = "/dev/null";
     };
+    suffix = lib.mkOption {
+      default = config.clan.core.machine.diskId;
+      defaultText = "abcdef";
+      type = lib.types.nullOr lib.types.str;
+      description = "The suffix to use for the disk";
+    };
   };
   config = {
+    assertions = [
+      {
+        assertion = cfg.suffix != null;
+        message = "clan.core.machine.diskId must be set, please run `clan facts generate`";
+      }
+    ];
     boot.loader.grub.efiSupport = lib.mkDefault true;
     boot.loader.grub.efiInstallAsRemovable = lib.mkDefault true;
-    disko.devices = {
+    disko.devices = lib.mkIf (cfg.suffix != null) {
       disk = {
         main = {
           type = "disk";
           # This is set through the UI
-          device = config.clan.single-disk.device;
+          device = cfg.device;
 
           content = {
             type = "gpt";
             partitions = {
-              "${config.networking.hostName}-boot" = {
+              "boot-${cfg.suffix}" = {
                 size = "1M";
                 type = "EF02"; # for grub MBR
                 priority = 1;
               };
-              "${config.networking.hostName}-ESP" = {
+              "ESP-${cfg.suffix}" = {
                 size = "512M";
                 type = "EF00";
                 content = {
@@ -36,7 +51,7 @@
                   mountpoint = "/boot";
                 };
               };
-              "${config.networking.hostName}-root" = {
+              "root-${cfg.suffix}" = {
                 size = "100%";
                 content = {
                   type = "filesystem";