This is a quick example of how to use kdb with a keyboard.
Configure kgdboc at boot using kernel parameters:
kgdboc=kbd
OR
Configure kgdboc after the kernel has booted:
echo kbd > /sys/module/kgdboc/parameters/kgdboc
Enter the kernel debugger manually or by waiting for an oops or fault. There are several ways you can enter the kernel debugger manually; all involve using the sysrq-g, which means you must have enabled CONFIG_MAGIC_SYSRQ=y in your kernel config.
When logged in as root or with a super user session you can run:
echo g > /proc/sysrq-trigger
Example using a laptop keyboard
Press and hold down: Alt
Press and hold down: Fn
Press and release the key with the label: SysRq
Release: Fn
Press and release: g
Release: Alt
Example using a PS/2 101-key keyboard
Press and hold down: Alt
Press and release the key with the label: SysRq
Press and release: g
Release: Alt
Now type in a kdb command such as "help", "dmesg", "bt" or "go" to continue kernel execution.