disks: support bios bootloader

Author: ibizaman

modules/beacon.nix

@@ -59,6 +59,7 @@ in {
       '';
       type = types.str;
       default = cfg.ip;
+      defaultText = "config.skarabox.ip";
     };
 
     hostname = lib.mkOption {
@@ -93,6 +94,7 @@ in {
         If installing on a cloud instance, set this to the port that can ssh into the instance as given by your cloud provider, usually 22.
       '';
       default = cfg.sshPort;
+      defaultText = "config.skarabox.sshPort";
     };
 
     sshAuthorizedKey = lib.mkOption {
@@ -121,6 +123,7 @@ in {
         If installing on a cloud instance, set this to the ssh key that can ssh into the instance as given by your cloud provider.
       '';
       default = cfg.sshAuthorizedKey;
+      defaultText = "config.skarabox.sshAuthorizedKey";
       apply = readAsListOfStr;
     };
   };

modules/disks.nix

@@ -44,6 +44,16 @@ in
             '';
             example = "100G";
           };
+
+          bootloader = mkOption {
+            type = types.enum [ "uefi" "bios" ];
+            description = ''
+              What bootloader mode to use.
+            '';
+            default = if config.hardware.facter.detected.uefi.supported then "uefi" else "bios";
+            defaultText = ''if config.hardware.facter.detected.uefi.supported then "uefi" else "bios"'';
+            example = "bios";
+          };
         };
       };
     };
@@ -114,6 +124,13 @@ in
           content = {
             type = "gpt";
             partitions = {
+              zfs = {
+                size = "100%";
+                content = {
+                  type = "zfs";
+                  pool = cfg.rootPool.name;
+                };
+              };
               ESP = {
                 size = "500M";
                 type = "EF00";
@@ -131,12 +148,11 @@ in
                   '';
                 };
               };
-              zfs = {
-                size = "100%";
-                content = {
-                  type = "zfs";
-                  pool = cfg.rootPool.name;
-                };
+            } // lib.optionalAttrs (cfg.rootPool.bootloader == "bios") {
+              boot = {
+                size = "1M";
+                type = "EF02";
+                attributes = [ 0 ];
               };
             };
           };
@@ -353,20 +369,22 @@ in
 
     # Setup Grub to support UEFI.
     # nodev is for UEFI.
-    boot.loader.grub = {
+    boot.loader.grub = let
+      isUEFI = cfg.rootPool.bootloader == "uefi";
+    in {
       enable = true;
-      efiSupport = true;
-      efiInstallAsRemovable = true;
+      efiSupport = isUEFI;
+      efiInstallAsRemovable = isUEFI;
 
       mirroredBoots = lib.mkForce ([
         {
           path = "/boot";
-          devices = [ "nodev" ];
+          devices = if isUEFI then [ "nodev" ] else [ cfg.rootPool.disk1 ];
         }
       ] ++ (optionals (cfg.rootPool.disk2 != null) [
         {
           path = "/boot-backup";
-          devices = [ "nodev" ];
+          devices = if isUEFI then [ "nodev" ] else [ cfg.rootPool.disk2 ];
         }
       ]));
     };

template/myskarabox/configuration.nix

@@ -25,6 +25,9 @@ in
         disk1 = "/dev/nvme0n1";  # Update with result of running `fdisk -l` on the beacon.
         disk2 = null;  # Set a value only if you have a second disk for the root partition.
         reservation = "500M";  # Set to 10% of size SSD.
+        # The bootloader - "uefi" or "bios" - should be detected from the facter.json.
+        # If the detected value is wrong, you can set it manually with the following option:
+        # bootloader = "bios";
       };
       skarabox.disks.dataPool = {
         enable = true;  # Disable if only an SSD for root is present.