nixos-rebuild: fix --install-bootloader flag with systemd-run

nixos/release-combined.nix

@@ -97,6 +97,8 @@ in rec {
         (onSystems ["x86_64-linux"] "nixos.tests.installer.simpleUefiSystemdBoot")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.simple")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.swraid")
+        (onSystems ["x86_64-linux"] "nixos.tests.nixos-rebuild-install-bootloader")
+        (onSystems ["x86_64-linux"] "nixos.tests.nixos-rebuild-specialisations")
         (onFullSupported "nixos.tests.ipv6")
         (onFullSupported "nixos.tests.keymap.azerty")
         (onFullSupported "nixos.tests.keymap.colemak")

nixos/tests/all-tests.nix

@@ -569,7 +569,8 @@ in {
   nix-serve-ssh = handleTest ./nix-serve-ssh.nix {};
   nixops = handleTest ./nixops/default.nix {};
   nixos-generate-config = handleTest ./nixos-generate-config.nix {};
-  nixos-rebuild-specialisations = handleTest ./nixos-rebuild-specialisations.nix {};
+  nixos-rebuild-install-bootloader = handleTestOn ["x86_64-linux"] ./nixos-rebuild-install-bootloader.nix {};
+  nixos-rebuild-specialisations = handleTest ["x86_64-linux"] ./nixos-rebuild-specialisations.nix {};
   nixpkgs = pkgs.callPackage ../modules/misc/nixpkgs/test.nix { inherit evalMinimalConfig; };
   node-red = handleTest ./node-red.nix {};
   nomad = handleTest ./nomad.nix {};

nixos/tests/nixos-rebuild-install-bootloader.nix

@@ -0,0 +1,73 @@
+import ./make-test-python.nix ({ pkgs, ... }: {
+  name = "nixos-rebuild-install-bootloader";
+
+  nodes = {
+    machine = { lib, pkgs, ... }: {
+      imports = [
+        ../modules/profiles/installation-device.nix
+        ../modules/profiles/base.nix
+      ];
+
+      nix.settings = {
+        substituters = lib.mkForce [ ];
+        hashed-mirrors = null;
+        connect-timeout = 1;
+      };
+
+      system.includeBuildDependencies = true;
+
+      virtualisation = {
+        cores = 2;
+        memorySize = 2048;
+      };
+
+      virtualisation.useBootLoader = true;
+    };
+  };
+
+  testScript =
+    let
+      configFile = pkgs.writeText "configuration.nix" ''
+        { lib, pkgs, ... }: {
+          imports = [
+            ./hardware-configuration.nix
+            <nixpkgs/nixos/modules/testing/test-instrumentation.nix>
+          ];
+
+          boot.loader.grub = {
+            enable = true;
+            device = "/dev/vda";
+            forceInstall = true;
+          };
+
+          documentation.enable = false;
+        }
+      '';
+
+    in
+    ''
+      machine.start()
+      machine.succeed("udevadm settle")
+      machine.wait_for_unit("multi-user.target")
+
+      machine.succeed("nixos-generate-config")
+      machine.copy_from_host(
+          "${configFile}",
+          "/etc/nixos/configuration.nix",
+      )
+      machine.succeed("nixos-rebuild switch")
+
+      # Need to run `nixos-rebuild` twice because the first run will install
+      # GRUB anyway
+      with subtest("Switch system again and install bootloader"):
+          result = machine.succeed("nixos-rebuild switch --install-bootloader")
+          # install-grub2.pl messages
+          assert "updating GRUB 2 menu..." in result
+          assert "installing the GRUB 2 boot loader on /dev/vda..." in result
+          # GRUB message
+          assert "Installation finished. No error reported." in result
+          # at this point we've tested regression #262724, but haven't tested the bootloader itself
+          # TODO: figure out how to how to tell the test driver to start the bootloader instead of
+          # booting into the kernel directly.
+    '';
+})

pkgs/os-specific/linux/nixos-rebuild/default.nix

@@ -32,6 +32,7 @@ substituteAll {
 
   # run some a simple installer tests to make sure nixos-rebuild still works for them
   passthru.tests = {
+    install-bootloader = nixosTests.nixos-rebuild-install-bootloader;
     simple-installer = nixosTests.installer.simple;
     specialisations = nixosTests.nixos-rebuild-specialisations;
   };

pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh

@@ -659,6 +659,7 @@ if [[ "$action" = switch || "$action" = boot || "$action" = test || "$action" =
     cmd=(
         "systemd-run"
         "-E" "LOCALE_ARCHIVE" # Will be set to new value early in switch-to-configuration script, but interpreter starts out with old value
+        "-E" "NIXOS_INSTALL_BOOTLOADER"
         "--collect"
         "--no-ask-password"
         "--pty"
@@ -679,7 +680,12 @@ if [[ "$action" = switch || "$action" = boot || "$action" = test || "$action" =
         cmd=()
     elif ! targetHostCmd "${cmd[@]}" true &>/dev/null; then
         logVerbose "Skipping systemd-run to switch configuration since it is not working in target host."
-        cmd=("env" "-i" "LOCALE_ARCHIVE=$LOCALE_ARCHIVE")
+        cmd=(
+            "env"
+            "-i"
+            "LOCALE_ARCHIVE=$LOCALE_ARCHIVE"
+            "NIXOS_INSTALL_BOOTLOADER=$NIXOS_INSTALL_BOOTLOADER"
+        )
     else
         logVerbose "Using systemd-run to switch configuration."
     fi