anchor.diff:      ] ++ optional cfg.useBootLoader
         { mountPoint = "/boot";
           device = "/dev/disk/by-label/boot";
  -        fsType = "ext3";
  +        fsType = "ext4";
           options = "ro";
           noCheck = true; # fsck fails on a r/o filesystem
         });
  
positive.code:           . /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.
  
negative.code:       # initialise.
        FSTYPE=$(blkid -o value -s TYPE /dev/vda || true)
        if test -z "$FSTYPE"; then
            mke2fs -t ext4 /dev/vda
        fi
      '';
  
  