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:       fi
      '';
  
    # After booting, register the closure of the paths in
    # `virtualisation.pathsInNixDB' in the Nix database in the VM.  This
    # allows Nix operations to work in the VM.  The path to the
    # registration file is passed through the kernel command line to
    # allow `system.build.toplevel' to be included.  (If we had a direct
    # reference to ${regInfo} here, then we would get a cyclic
    # dependency.)
    boot.postBootCommands =
      ''
        ( source /proc/cmdline
          ${config.environment.nix}/bin/nix-store --load-db < $regInfo
        )
      '';
        
    virtualisation.pathsInNixDB = [ config.system.build.toplevel ];
    
    # Mount the host filesystem via CIFS, and bind-mount the Nix store
    # of the host into our own filesystem.  We use mkOverride to allow
    # this module to be applied to "normal" NixOS system configuration,
  