C and Assembly( your gonna need the asm / microprocessor internals knowledge). Also I'd recommend minix as a start http://www.minix3.org/ http://www.minix3.org/

C and Assembly( your gonna need the asm / microprocessor internals knowledge). Also I'd recommend minix as a start http://www.minix3.org/ http://www.minix3.org/, here's a really basic intro to drivers to give you the basic idea what that entails, http://www.freesoftwaremagazine.com/articles/drivers_linux http://www.freesoftwaremagazine.com/articles/drivers_linux. One thing, if you're just starting out (which it sounds like), I would NOT recommend looking at the linux kernel src. And lastly, modern operating systems by tanenbaum is a good introductory text that has the plus of being a fun read. Good luck!