Entering the KDB kernel debugger

You can enter the KDB kernel debugger using several different procedures.

Enter the KDB kernel debugger using one of the following procedures:

On a tty keyboard, press the Ctrl+4 key sequence for IBM 3151 terminals or the Ctrl+\ key sequence for BQ 303, BQ 310C, and WYSE 50 terminals.
On other keyboards, press the Ctrl+Alt+Numpad4 key sequence.
Set a breakpoint using one of the Breakpoint and steps subcommands.
Call the brkpoint subroutine from the C code. The syntax for calling this subroutine is the following:
```
 brkpoint();
```

Note: The system enters the debugger if a system halt is caused by a fatal system error. In such a case, the system creates a log entry in the system log and if the KDB kernel debugger is available, it is called. A system dump might be generated when you exit from the debugger.

If the kernel debug program is not available when you type in a key sequence, you must load the kernel debug program.

For more information about loading the kernel debug program, seer Loading and starting the KDB kernel debugger.

You can use the kdb command with the dw subcommand to determine whether the KDB kernel debugger is available by typing the following:

     # kdb 
     (0)> dw kdb_avail
     (0)> dw kdb_wanted

Note: If either of the previous dw subcommands returns a 0, the KDB kernel debugger is not available.

After the KDB kernel debugger is invoked, the subcommands detailed in Subcommand lists are available.