* Added a command `nixos-rebuild build-vm-with-bootloader'. This is

like `build-vm', but boots using the regular boot loader (i.e. GRUB
  1 or 2) rather than booting directly from the kernel/initrd.  Thus
  it allows testing of GRUB.

svn path=/nixos/trunk/; revision=23747

default.nix

@@ -11,11 +11,22 @@ let
 
   inherit (eval) config pkgs;
 
+  # This is for `nixos-rebuild build-vm'.
   vmConfig = (import ./lib/eval-config.nix {
     inherit system;
     modules = [ configuration ./modules/virtualisation/qemu-vm.nix ];
   }).config;
-    
+
+  # This is for `nixos-rebuild build-vm-with-bootloader'.
+  vmWithBootLoaderConfig = (import ./lib/eval-config.nix {
+    inherit system;
+    modules =
+      [ configuration
+        ./modules/virtualisation/qemu-vm.nix
+        { virtualisation.useBootLoader = true; }
+      ];
+  }).config;
+      
 in
 
 {
@@ -25,6 +36,8 @@ in
 
   vm = vmConfig.system.build.vm;
 
+  vmWithBootLoader = vmWithBootLoaderConfig.system.build.vm;
+
   # The following are used by nixos-rebuild.
   nixFallback = pkgs.nixUnstable;
   manifests = config.installer.manifests;

doc/manual/man-nixos-rebuild.xml

@@ -24,6 +24,8 @@
       <arg choice='plain'><option>build</option></arg>
       <arg choice='plain'><option>dry-run</option></arg>
       <arg choice='plain'><option>build-vm</option></arg>
+      <arg choice='plain'><option>build-vm-with-bootloader</option></arg>
+      <arg choice='plain'><option>pull</option></arg>
     </group>
     <sbr />
     <arg><option>--install-grub</option></arg>
@@ -151,6 +153,35 @@ $ ./result/bin/run-*-vm
     </listitem>
   </varlistentry>
 
+  <varlistentry>
+    <term><option>build-vm-with-bootloader</option></term>
+    <listitem>
+      <para>Like <option>build-vm</option>, but boots using the
+      regular boot loader of your configuration (e.g., GRUB 1 or 2),
+      rather than booting directly into the kernel and initial ramdisk
+      of the system.  This allows you to test whether the boot loader
+      works correctly.  However, it does not guarantee that your NixOS
+      configuration will boot successfully on the host hardware (i.e.,
+      after running <command>nixos-rebuild switch</command>), because
+      the hardware and boot loader configuration in the VM are
+      different.  The boot loader is installed on an automatically
+      generated virtual disk containing a <filename>/boot</filename>
+      partition, which is mounted read-only in the VM.</para>
+    </listitem>
+  </varlistentry>
+  
+  <varlistentry>
+    <term><option>pull</option></term>
+    <listitem>
+      <para>This operation merely fetches the latest manifest in the
+      Nixpkgs channel to speed up subsequent
+      <command>nix-env</command> operations.  This is useful if you
+      are not using <command>nix-channel</command> but still want to
+      use pre-built binary packages.  It doesn’t reconfigure the
+      system at all.</para>
+    </listitem>
+  </varlistentry>
+
 </variablelist>
 
 </para>

modules/installer/tools/nixos-rebuild.sh

@@ -22,6 +22,8 @@ The operation is one of the following:
             activate it
   build-vm: build a virtual machine containing the configuration
             (useful for testing)
+  build-vm-with-bootloader:
+            like build-vm, but include a boot loader in the VM
   dry-run:  just show what store paths would be built/downloaded
   pull:     just pull the Nixpkgs channel manifest and exit
 
@@ -64,7 +66,7 @@ while test "$#" -gt 0; do
       --help)
         showSyntax
       ;;
-      switch|boot|test|build|dry-run|build-vm|pull)
+      switch|boot|test|build|dry-run|build-vm|build-vm-with-bootloader|pull)
         action="$i"
       ;;
       --install-grub)
@@ -171,9 +173,12 @@ if test -z "$rollback"; then
     elif test "$action" = test -o "$action" = build -o "$action" = dry-run; then
         nix-build $NIXOS -A system -K -k $extraBuildFlags > /dev/null
         pathToConfig=./result
-    elif test "$action" = build-vm; then
+    elif [ "$action" = build-vm ]; then
         nix-build $NIXOS -A vm -K -k $extraBuildFlags > /dev/null
         pathToConfig=./result
+    elif [ "$action" = build-vm-with-bootloader ]; then
+        nix-build $NIXOS -A vmWithBootLoader -K -k $extraBuildFlags > /dev/null
+        pathToConfig=./result
     else
         showSyntax
     fi

modules/system/activation/switch-to-configuration.sh

@@ -38,7 +38,7 @@ if [ "$action" = "switch" -o "$action" = "boot" ]; then
 
               if [ "$NIXOS_INSTALL_GRUB" = 1 -o "$oldGrubVersion" != "$newGrubVersion" ]; then
                   echo "installing the GRUB bootloader..."
-                  @grub@/sbin/grub-install "@grubDevice@" --no-floppy --recheck
+                  @grub@/sbin/grub-install "@grubDevice@" --no-floppy
                   echo "$newGrubVersion" > /boot/grub/version
               fi
           fi

modules/virtualisation/qemu-vm.nix

@@ -110,7 +110,24 @@ let
         example = "-vga std";
         description = "Options passed to QEMU.";
       };
-      
+
+    virtualisation.useBootLoader =
+      mkOption {
+        default = true;
+        description =
+          ''
+            If enabled, the virtual machine will be booted using the
+            regular boot loader (i.e., GRUB 1 or 2).  This allows
+            testing of the boot loader.  However, it does not
+            guarantee that your NixOS configuration will boot
+            successfully on the host hardware, because the hardware
+            and boot loader configuration in the VM are different.  If
+            disabled (the default), the VM directly boots the NixOS
+            kernel and initial ramdisk, bypassing the boot loader
+            altogether.
+          '';
+      };
+            
   };
 
   cfg = config.virtualisation;
@@ -146,12 +163,17 @@ let
           -net nic,vlan=0,model=virtio \
           -chardev socket,id=samba,path=./samba \
           -net user,vlan=0,guestfwd=tcp:10.0.2.4:139-chardev:samba''${QEMU_NET_OPTS:+,$QEMU_NET_OPTS} \
-          -drive file=$NIX_DISK_IMAGE,if=virtio,boot=on,cache=writeback,werror=report \
-          -kernel ${config.system.build.toplevel}/kernel \
-          -initrd ${config.system.build.toplevel}/initrd \
+          ${if cfg.useBootLoader then ''
+            -drive index=0,file=$NIX_DISK_IMAGE,if=virtio,cache=writeback,werror=report \
+            -drive index=1,file=${bootDisk}/disk.img,if=virtio,boot=on \
+          '' else ''
+            -drive file=$NIX_DISK_IMAGE,if=virtio,boot=on,cache=writeback,werror=report \
+            -kernel ${config.system.build.toplevel}/kernel \
+            -initrd ${config.system.build.toplevel}/initrd \
+            -append "$(cat ${config.system.build.toplevel}/kernel-params) init=${config.system.build.bootStage2} systemConfig=${config.system.build.toplevel} regInfo=${regInfo} ${kernelConsole} $QEMU_KERNEL_PARAMS" \
+          ''}
           ${qemuGraphics} \
           $QEMU_OPTS \
-          -append "$(cat ${config.system.build.toplevel}/kernel-params) init=${config.system.build.bootStage2} systemConfig=${config.system.build.toplevel} regInfo=${regInfo} ${kernelConsole} $QEMU_KERNEL_PARAMS" \
           ${config.virtualisation.qemu.options}
     '';
 
@@ -165,11 +187,54 @@ let
       printRegistration=1 perl ${pkgs.pathsFromGraph} closure-* > $out
     '';
 
+
+  # Generate a hard disk image containing a /boot partition and GRUB
+  # in the MBR.  Used when the `useBootLoader' option is set.
+  bootDisk =
+    pkgs.vmTools.runInLinuxVM (
+      pkgs.runCommand "nixos-boot-disk"
+        { preVM =
+            ''
+              mkdir $out
+              diskImage=$out/disk.img
+              ${pkgs.vmTools.kvm}/bin/qemu-img create -f qcow2 $diskImage "32M"
+            '';
+          buildInputs = [ pkgs.utillinux ];
+        }
+        ''
+          # Create a single /boot partition.
+          ${pkgs.parted}/sbin/parted /dev/vda mklabel msdos
+          ${pkgs.parted}/sbin/parted /dev/vda -- mkpart primary ext2 1M -1s
+          . /sys/class/block/vda1/uevent
+          mknod /dev/vda1 b $MAJOR $MINOR
+          . /sys/class/block/vda/uevent
+          ${pkgs.e2fsprogs}/sbin/mkfs.ext3 -L boot /dev/vda1
+          ${pkgs.e2fsprogs}/sbin/tune2fs -c 0 -i 0 /dev/vda1
+
+          # Mount /boot.
+          mkdir /boot
+          mount /dev/vda1 /boot
+
+          # This is needed for GRUB 0.97, which doesn't know about virtio devices.
+          mkdir /boot/grub
+          echo '(hd0) /dev/vda' > /boot/grub/device.map
+
+          # Install GRUB and generate the GRUB boot menu.
+          touch /etc/NIXOS 
+          mkdir -p /nix/var/nix/profiles
+          ${config.system.build.toplevel}/bin/switch-to-configuration boot
+
+          umount /boot
+        ''
+    );
+    
 in
 
 {
   require = options;
 
+  boot.loader.grub.device = mkOverride 50 "/dev/vda";
+  
   # All the modules the initrd needs to mount the host filesystem via
   # CIFS.  Also use paravirtualised network and block devices for
   # performance.
@@ -207,6 +272,7 @@ in
 
   boot.initrd.postMountCommands =
     ''
+      mkdir -p $targetRoot/boot
       mount -o remount,ro $targetRoot/nix/store
       ${optionalString cfg.writableStore ''
         mkdir /mnt-store-tmpfs
@@ -225,7 +291,9 @@ in
   boot.postBootCommands =
     ''
       ( source /proc/cmdline
-        ${config.environment.nix}/bin/nix-store --load-db < $regInfo
+        if [ -n "$regInfo" ]; then
+            ${config.environment.nix}/bin/nix-store --load-db < $regInfo
+        fi
       )
     '';
       
@@ -237,7 +305,7 @@ in
   # where the regular value for the `fileSystems' attribute should be
   # disregarded for the purpose of building a VM test image (since
   # those filesystems don't exist in the VM).
-  fileSystems = mkOverride 50
+  fileSystems = mkOverride 50 (
     [ { mountPoint = "/";
         device = "/dev/vda";
       }
@@ -253,7 +321,15 @@ in
         options = "bind";
         neededForBoot = true;
       }
-    ];
+    ] ++ optional cfg.useBootLoader
+      { mountPoint = "/boot";
+        device = "/dev/disk/by-label/boot";
+        fsType = "ext3";
+        options = "ro";
+        noCheck = true; # fsck fails on a r/o filesystem
+      });
+
+  swapDevices = mkOverride 50 [ ];
 
   # Starting DHCP brings down eth0, which kills the connection to the
   # host filesystem and thus deadlocks the system.