Enabling the Target System s Debug Client

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[oR]

Enabling the Target System's Debug Client

Both the retail and checked (debug) versions of Windows 2000 include a debugging client that allows the kernel to communicate over a serial line with the WinDbg debugger. The debug client must be enabled on the target system during the boot process.

To enable the debug client, select the OS for the target machine with cursor keys while the system boot screen is displayed. Press F8 and select (with cursor keys) the option for Debugging Mode. Press Enter twice to boot the system.

By default, the debug client uses the COM2 port, configured for 19200 baud. These are the same defaults used by WinDbg. To use a different port or baud rate, the BOOT.INI file located on the boot partition root must be modified.

Modifying BOOT.INI

The BOOT.INI file is a read-only, hidden file located on the boot partition's root directory. To edit it, these attributes must be removed. Windows Explorer works well, or the ATTRIB utility of the command prompt can be used.

 attrib -s -h -r BOOT.INI 

Then the file is modified using any familiar text editor, such as Notepad. The file is similar in structure to an INI file and contains a section labeled [operating systems]. Each entry (line) within this section is displayed on the system boot screen as a choice for user selection. (A timeout value located in the [boot loader] section specifies how long the user has to make this choice.)

The format of each line of the [operating systems] section includes an ARC-style path to a specific drive, partition, and directory, which holds kernel files. An ="Description" value specifies the text shown to the user on the boot screen for the selection.

An example of a BOOT.INI file is

 [boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(2)\WINNT [operating systems] multi(0)disk(0)rdisk(0)partition(2)\WINNT="W2K Pro" /fastdetect C:\="Microsoft Windows" 

To specify a boot option for debugging, switches are added to an existing or new [operating systems] entry. The relevant switches for debugging are listed in Table A.3.

Table A.3. Debugging Options for BOOT.INI

BOOT.INI Options
Option	Description
/DEBUG	Enables kernel debug client
/NODEBUG	Disables debug client (default)
/DEBUGPORT=PortName	Specifies COMn port to use
/BAUDRATE=BaudRate	Specifies baud rate for COM port
/CRASHDEBUG	Causes debugger to activate only upon system bugcheck
/SOS	Displays list of modules loaded while system starts
/MAXMEM=MBSize	Specifies maximum memory available to this boot (for testing with smaller memory configurations)

An example entry to allow the user to select a debug client on COM port 4, with a baud rate of 38.4 KBaud, would be:

 multi(0)disk(0)rdisk(0)partition(2)\WINNT="W2K Debug" /debugport=COM4 /baudrate=38400 

If two different kernels are installed on the same system, they must reside in different directories. The [operating systems] entry would specify the appropriate directory instead of WINNT.

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