Learning OS programming?

Hi Guys. I am a freshman in Computer Science and wanna specialize in OS. if i wait for university to teach me,it would take 2 or more. By now i only know about C programming at some rate. My question is what do i have to learn to understand and write my own OS(at least like sipmle linux-s),and in which order that is the best ? and some good books & refs on these. What i need is clear path for beginning, whatever it takes i`ll learn anyway :)

for example, c-->algorithms-->assembly&machine-->kernel.....etc tnx iimushka