From fd110f5fea05d13f14621b41d361ce3d7346fd32 Mon Sep 17 00:00:00 2001
From: Raito Bezarius <masterancpp@gmail.com>
Date: Fri, 28 Apr 2023 17:01:22 +0200
Subject: nixos/tests/netboot: add directBoot test

This verifies that we can direct boot a netboot image as expected.
---
 nixos/modules/installer/netboot/netboot.nix | 30 ++++++++++++++++++++++++++++-
 nixos/tests/boot.nix                        |  9 +++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/nixos/modules/installer/netboot/netboot.nix b/nixos/modules/installer/netboot/netboot.nix
index a50f22cbe471..fb9b6541853c 100644
--- a/nixos/modules/installer/netboot/netboot.nix
+++ b/nixos/modules/installer/netboot/netboot.nix
@@ -1,7 +1,7 @@
 # This module creates netboot media containing the given NixOS
 # configuration.
 
-{ config, lib, pkgs, ... }:
+{ options, config, lib, pkgs, ... }:
 
 with lib;
 
@@ -41,6 +41,34 @@ with lib;
     environment.systemPackages = [ pkgs.grub2_efi ]
       ++ (lib.optionals (pkgs.stdenv.hostPlatform.system != "aarch64-linux") [pkgs.grub2 pkgs.syslinux]);
 
+    # We only want to set those options in the context of
+    # the QEMU infrastructure.
+    virtualisation = lib.optionalAttrs (options ? virtualisation.directBoot) {
+      # By default, using netboot images in virtualized contexts
+      # should not create any disk image ideally, except if
+      # asked explicitly.
+      diskImage = mkDefault null;
+      # We do not want to mount the host Nix store in those situations.
+      mountHostNixStore = mkDefault false;
+      # We do not need the nix store image because:
+      # - either we boot through network and we have the squashfs image
+      # - either we direct boot, we have the squashfs image
+      useNixStoreImage = mkDefault false;
+      # Though, we still want a writable store through .rw-store
+      writableStore = mkDefault true;
+      # Ideally, we might not want to test the network / firmware.
+      directBoot = {
+        enable = mkDefault true;
+        # We need to use our netboot initrd which contains a copy of the Nix store.
+        initrd = "${config.system.build.netbootRamdisk}/${config.system.boot.loader.initrdFile}";
+      };
+      # We do not want to use the default filesystems.
+      useDefaultFilesystems = mkDefault false;
+      # Bump the default memory size as we are loading the whole initrd in RAM.
+      memorySize = mkDefault 1536;
+    };
+
+
     fileSystems."/" = mkImageMediaOverride
       { fsType = "tmpfs";
         options = [ "mode=0755" ];
diff --git a/nixos/tests/boot.nix b/nixos/tests/boot.nix
index ec2a9f6527c9..11fb817c77a7 100644
--- a/nixos/tests/boot.nix
+++ b/nixos/tests/boot.nix
@@ -104,6 +104,15 @@ in {
       bios = uefiBinary;
     };
 
+    directNetboot = makeTest {
+      name = "directboot-netboot";
+      nodes.machine = {
+        imports = [ ../modules/installer/netboot/netboot-minimal.nix ];
+        virtualisation.memorySize = 4096;
+      };
+      testScript = "machine.fail('stat /dev/vda')";
+    };
+
     uefiNetboot = makeNetbootTest "uefi" {
       bios = uefiBinary;
       # Custom ROM is needed for EFI PXE boot. I failed to understand exactly why, because QEMU should still use iPXE for EFI.
-- 
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