anchor.diff:          options = "bind";
           neededForBoot = true;
         }
  -      # Mount the host's Nix database.  This allows read-only Nix
  -      # operations in the guest to work properly.
  -      { mountPoint = "/nix/var/nix/db";
  -        device = "/hostfs/nix/var/nix/db";
  -        options = "bind";
  -      }
       ];
   
     # Starting DHCP brings down eth0, which kills the connection to the
  
positive.code:         default = true;
          description =
            ''
              Whether to run qemu with a graphics window, or access
              the guest computer serial port through the host tty.
            '';
        };
  
    };
  
    cfg = config.virtualisation;
  
negative.code:           -initrd ${config.system.build.toplevel}/initrd \
            ${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"
      '';
  
      
    regInfo = pkgs.runCommand "reginfo"
      { exportReferencesGraph =
          map (x: [("closure-" + baseNameOf x) x]) config.virtualisation.pathsInNixDB;
        buildInputs = [ pkgs.perl ];
      }
      ''
        printRegistration=1 perl ${pkgs.pathsFromGraph} closure-* > $out
      '';
  
  in
  