Re-write Linux Kernel and debug? [closed]

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http://stackoverflow.com – (Assume a newbie Linux programmer but someone who can write code very well) I'd like to make a few changes in the Linux kernel to customize a few things. What stages would I take to do this and is there any way I could effectively "run" the Kernel in some sort of debugger and step-through the executing code? How would I go about doing this? (HowTos)