nixos: iPXE client for GRUB

fix bug in grub/install-grub.pl that would replace @bootRoot@ with an invalid string

nixos/modules/module-list.nix

@@ -359,6 +359,7 @@
   ./system/boot/loader/efi.nix
   ./system/boot/loader/generations-dir/generations-dir.nix
   ./system/boot/loader/grub/grub.nix
+  ./system/boot/loader/grub/ipxe.nix
   ./system/boot/loader/grub/memtest.nix
   ./system/boot/loader/gummiboot/gummiboot.nix
   ./system/boot/loader/init-script/init-script.nix

nixos/modules/system/boot/loader/grub/install-grub.pl

@@ -341,8 +341,9 @@ addEntry("NixOS - Default", $defaultConfig);
 
 $conf .= "$extraEntries\n" unless $extraEntriesBeforeNixOS;
 
+my $grubBootPath = $grubBoot->path;
 # extraEntries could refer to @bootRoot@, which we have to substitute
-$conf =~ s/\@bootRoot\@/$grubBoot->path/g;
+$conf =~ s/\@bootRoot\@/$grubBootPath/g;
 
 # Emit submenus for all system profiles.
 sub addProfile {

nixos/modules/system/boot/loader/grub/ipxe.nix

@@ -0,0 +1,64 @@
+# This module adds a scripted iPXE entry to the GRUB boot menu.
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  scripts = builtins.attrNames config.boot.loader.grub.ipxe;
+
+  grubEntry = name:
+    ''
+      menuentry "iPXE - ${name}" {
+        linux16 @bootRoot@/ipxe.lkrn
+        initrd16 @bootRoot@/${name}.ipxe
+      }
+
+    '';
+
+  scriptFile = name:
+    let
+      value = builtins.getAttr name config.boot.loader.grub.ipxe;
+    in
+    if builtins.typeOf value == "path" then value
+    else builtins.toFile "${name}.ipxe" value;
+in
+{
+  options =
+    { boot.loader.grub.ipxe = mkOption {
+        type = types.attrsOf (types.either types.path types.str);
+        description =
+          ''
+            Set of iPXE scripts available for
+            booting from the GRUB boot menu.
+          '';
+        default = { };
+        example = literalExample ''
+          { demo = '''
+              #!ipxe
+              dhcp
+              chain http://boot.ipxe.org/demo/boot.php
+            ''';
+          };
+        '';
+      };
+    };
+
+  config = mkIf (builtins.length scripts != 0) {
+
+    boot.loader.grub.extraEntries =
+      if config.boot.loader.grub.version == 2 then
+        toString (map grubEntry scripts)
+      else
+        throw "iPXE is not supported with GRUB 1.";
+
+    boot.loader.grub.extraFiles =
+      { "ipxe.lkrn" = "${pkgs.ipxe}/ipxe.lkrn"; }
+      //
+      builtins.listToAttrs ( map
+        (name: { name = name+".ipxe"; value = scriptFile name; })
+        scripts
+      );
+  };
+
+}