kgdb is a source level debugger for linux kernel. It is used along with gdb to debug a linux kernel. The expectation is that gdb can be used to "break in" to the kernel to inspect memory, variables and look through call stack information similar to what an application developer would use gdb for. It is possible to place breakpoints in kernel code and perform some limited execution stepping.

Two machines are required for using kgdb. One of these machines is a development machine and the other is a test machine. The kernel to be debugged runs on the test machine. The development machine runs an instance of gdb against the vmlinux file which contains the symbols (not boot image such as bzImage, zImage, uImage...). In gdb the developer specifies the connection parameters and connects to kgdb. The type of connection a developer makes with gdb depends on the availability of kgdb I/O modules compiled as builtin's or kernel modules in the test machine's kernel.