PVM provides a simple but extensible debugging facility. Tasks started by hand could just as easily be run under a debugger, but this procedure is cumbersome for those spawned by an application, since it requires the user to comment out the calls to pvm_spawn() and start tasks manually. If PvmTaskDebug is added to the flags passed to pvm_spawn(), the task is started through a debugger script (a normal shell script), $PVM_ROOT/lib/debugger.
The pvmd passes the name and parameters of the task to the debugger script, which is free to start any sort of debugger. The script provided is very simple. In an xterm window, it runs the correct debugger according to the architecture type of the host. The script can be customized or replaced by the user. The pvmd can be made to execute a different debugger via the bx= host file option or the PVM_DEBUGGER environment variable.