anchor.diff:        "--register"
       ];
   
  -    vmFlags = mkFlags [
  +    vmFlags = mkFlags ([
         "--uart1 0x3F8 4"
         "--uartmode1 client /run/virtualbox-log-${name}.sock"
  -    ];
  +    ] ++ (attrs.vmFlags or []));
   
       controllerFlags = mkFlags [
         "--name SATA"
  
positive.code: 
      services.virtualboxGuest.enable = true;
  
      boot.initrd.kernelModules = [ "vboxsf" ];
  
      boot.initrd.extraUtilsCommands = ''
        cp -av -t "$out/bin/" \
          "${pkgs.linuxPackages.virtualboxGuestAdditions}/sbin/mount.vboxsf"
      '';
  
      boot.initrd.postMountCommands = ''
        touch /mnt-root/boot-done
  
        i=0
        while [ ! -e /mnt-root/shutdown ]; do
          sleep 10
          i=$(($i + 10))
          [ $i -le 120 ] || fail
        done
  
        rm -f /mnt-root/boot-done /mnt-root/shutdown
        poweroff -f
      '';
  
  
negative.code:       mkVMConf = name: val: val.machine // { key = "${name}-config"; };
        vmConfigs = mapAttrsToList mkVMConf vboxVMs;
      in [ ./common/user-account.nix ./common/x11.nix ] ++ vmConfigs;
      virtualisation.memorySize = 768;
      services.virtualboxHost.enable = true;
      users.extraUsers.alice.extraGroups = [ "vboxusers" ];
    };
  
    testScript = ''
      sub ru ($) {
        my $esc = $_[0] =~ s/'/'\\${"'"}'/gr;
        return "su - alice -c '$esc'";
      }
  
      sub vbm {
  