build netboot files from hydra

flake.nix

@@ -114,7 +114,7 @@
       public01.imports = commonModules ++ [ ./hosts/public01 ];
     } // builders;
 
-    hydraJobs = builtins.mapAttrs (n: v: v.config.system.build.toplevel) self.nixosConfigurations;
+    hydraJobs = builtins.mapAttrs (n: v: v.config.system.build.netbootDir or v.config.system.build.toplevel) self.nixosConfigurations;
     buildbotJobs = builtins.mapAttrs (_: v: v.config.system.build.toplevel) self.nixosConfigurations;
   };
 }

services/baremetal-builder/default.nix

@@ -1,4 +1,4 @@
-{ pkgs, lib, config, ... }:
+{ pkgs, lib, config, extendModules, ... }:
 let
   cfg = config.bagel.baremetal.builders;
 in
@@ -177,6 +177,39 @@ in
 
     environment.systemPackages = [ pkgs.ipmitool ];
 
+    system.build = lib.mkIf cfg.netboot {
+      netbootVariant = extendModules {
+        modules = [
+          (
+            { modulesPath, ... }:
+
+            {
+              imports = [ (modulesPath + "/installer/netboot/netboot.nix") ];
+            }
+          )
+        ];
+      };
+      netbootDir = let
+        kernelTarget = pkgs.stdenv.hostPlatform.linux-kernel.target;
+        build = config.system.build.netbootVariant.config.system.build;
+      in
+        pkgs.symlinkJoin {
+          name = "netboot";
+          paths = [
+            build.netbootRamdisk
+            build.kernel
+            build.netbootIpxeScript
+          ];
+          postBuild = ''
+            mkdir -p $out/nix-support
+            echo "file ${kernelTarget} ${build.kernel}/${kernelTarget}" >> $out/nix-support/hydra-build-products
+            echo "file initrd ${build.netbootRamdisk}/initrd" >> $out/nix-support/hydra-build-products
+            echo "file ipxe ${build.netbootIpxeScript}/netboot.ipxe" >> $out/nix-support/hydra-build-products
+          '';
+          preferLocalBuild = true;
+        };
+    };
+
     system.stateVersion = "24.05";
   };
 }