Kernel-Mode Environment Variables

The following table lists the environment variables that are used only in kernel-mode debugging.

Variable Meaning


Specifies the COM port to be used in a kernel connection. For details, see Getting Set Up for Debugging.


Specifies the baud rate to be used over the COM port connection.

_NT_DEBUG_BUS = 1394

Specifies that kernel debugging will be done over a 1394 cable connection.

_NT_DEBUG_1394_CHANNEL = 1394Channel

Specifies the channel to be used for the 1394 kernel connection.

_NT_DEBUG_1394_SYMLINK = Protocol

Specifies the connection protocol to be used for the 1394 kernel connection.

KDQUIET =Anything

If KDQUIET is defined, the debugger will run in quiet mode. Quiet mode involves three distinct effects:

1. The debugger does not display messages each time an extension DLL is loaded or unloaded.

2. The r (Registers) command no longer requires an equal sign in its syntax.

3. The debugger will not display a warning message when breaking into the target computer.

Quiet mode can also be controlled by using the sq (Set Quiet Mode) command.


Specifies the maximum kernel debugging cache size, in bytes. This cache holds data received by the host computer from the serial connection. The default is 1,024,000.


Specifies one of the following two values:

NOEXTWARNING tells the debugger not to output a warning when it cannot find an extension command.

NOVERSIONCHECK tells the debugger not to check the version of debugger extensions.

These options can be modified or displayed by using the so (Set Kernel Options) command.

_NT_KD_FILES = MapFile

Specifies a driver replacement map file. For details and for other methods of controlling driver replacement, see Mapping Driver Files.

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