Article ID: 6618, created on Aug 15, 2009, last review on Feb 27, 2016

  • Applies to:
  • Virtuozzo containers for Windows


Sometimes it is necessary to configure two servers connected with a null-modem cable to facilitate deep kernel investigation.

Serial Console is a machine with access to the network, so it can be reached by the outside world.


  1. Connect the target server to another Windows machine (client) via a null-modem cable using COM ports;
  2. Download and install Microsoft debugging tools to the client machine;
  3. Refer to this Microsoft article to configure the PVC host for debugging. Follow the "Debugging with a null-modem cable" section of the article;
  4. Check that the connection is working properly using Hyper Terminal. Run Hyper Terminal on both computers; choose the COM ports you used for the connection, and type any text within any part of Hyper Terminal. All typed text should be displayed in another Hyper Terminal. This means that the connection is working properly;
  5. Reboot the PVC host to apply the debug options. Keep in mind that after the reboot, Hyper Terminal cannot be used for testing because the server will be switched to debug mode and the COM ports will be dedicated to the debugger.
If there is an issue with connectivity between COM ports on step 4, or the debugger cannot connect to the COM port after the reboot, it is recommended to check the following:

1. Check the COM port options in the BIOS of the server;
2. Using bcdedit /dbgsettings, find the COM port settings and make sure they are correct;
3. Run bcdedit and make sure the detecthal, usefirmwarepcisettings, and debug parameters are set to Yes;
4. Try a lower baud-rate or different COM port;
5. Try replacing the cable;
6. Try to use the IEEE 1394 port present on the PVC host; use it as a debugger connection. Refer to the "Debugging with an IEEE 1394 cable" portion of this article for configuration steps;
7. Try using another machine as a target;
8. Try to apply the bcdedit /bootdebug yes command.

In some cases, it is necessary to disable the "flow control" feature on the host network adapters. This is required if the local network switch is not compatible with the adapter's "flow control" feature and blocks all network traffic when a single adapter is stopped.

Check the following for all involved machines’ network connections:
Connection Properties->Configure->Advanced->Flow control = Disabled (exact path may vary depending on the NIC vendor)

Additional information

Related Microsoft articles:
Boot Parameters to Enable Debugging
How to set up a remote debug session using a null-modem cable

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