"Kernel GNU debugger, kgdb
"The kgdb developed initially as a patch is now included in the
official 2.6.26 kernel. This source level debugging tool is much
easier to use. It requires two machines to be connected via a
serial connection (a RS-232 interface using null modem/a UDP/IP
networking protocol). The gdb is used along with kgdb to trace
through kernel code. The gdb runs on the host machine and the kgdb
patched kernel runs on the target machine.
"GNU debugger, gdb
"This is also a powerful stand alone tool used for debugging. But
with this tool you can’t set the breakpoint or trace the
kernel code. Instead you can use gdb to debug the core files which
are dumped when an error occurs."