"The Linux kernel debugger (KDB) allows you to debug the Linux
kernel. This aptly named tool is essentially a patch to the kernel
code that lets hackers access kernel memory and data structures.
One of the main advantages of KDB is that it does not require an
additional machine for debugging: you can debug the kernel that you
are running on.
"Setting up a machine for KDB requires a little work in that the
kernel needs to be patched and recompiled. Users of KDB should be
familiar with compiling the Linux kernel (and with kernel
internals, to an extent), but refer to the Resources section at the
end of this article if you need help compiling the kernel.
"In this article we'll start with information on downloading KDB
patches, applying them, (re)compiling the kernel, and starting KDB.
Then we'll get into the KDB commands and review some of the more
often-used commands. Finally, we'll look at some details about the
setup and display options..."