anchor.diff:      quit
       CMD
       wait %-
  +
  +    eval "$postVM"
  +    exit 0
  +  '' else if installMode then ''
  +    eval "$postVM"
  +    exit 0
  +  '' else ''
  +    if ! test -e "$XCHG_DIR/in-vm-exit"; then
  +      echo "Virtual machine didn't produce an exit code."
  +      exit 1
  +    fi
  +
  +    eval "$postVM"
  +    exit $(< "$XCHG_DIR/in-vm-exit")
     '';
   
   in writeScript "run-cygwin-vm.sh" ''
     #!${stdenv.shell} -e
     ${preVM}
     ${vmExec}
  +  ${postVM}
   ''
  
positive.code:     (set; declare -p) > saved-env
      XCHG_DIR="$(${coreutils}/bin/mktemp -d nix-vm.XXXXXXXXXX --tmpdir)"
      ${coreutils}/bin/mv saved-env "$XCHG_DIR/"
      QEMU_VDE_SOCKET="$(pwd)/vde.ctl"
      MONITOR_SOCKET="$(pwd)/monitor"
      ${vde2}/bin/vde_switch -s "$QEMU_VDE_SOCKET" &
  
negative.code:       -i /ssh.key \
        -l Administrator \
        192.168.0.1 -- ${shellEscape command}
    '') + lib.optionalString (suspendTo != null) ''
      ${coreutils}/bin/touch /xchg/suspend_now
      ${loopForever}
    '');
  
    kernelAppend = lib.concatStringsSep " " [
      "panic=1"
  