OSDev.org

lets say I want to set up a IDT, but the only thing Im interrested in is an IRQ...so my IDT would just be filled with gibberish except for this special IRQ..
but if e.g. an exception occurs.. the CPU will then try to run a ISR, but since I only filled my IDT with information about the IRQ interrupt, what will happen? It will try to read the IDT(which is initialized to about anything)? Cause I read I only need to fill the IDT wherever I want, and right now I dont care about exceptions..but if they occur, what happens if I havent filled in the "Beginning of the IDT, exceptions"?

Triple fault resulting in reboot.

really, i *strongly* suggest you at least put a "cli; hlt" handler in your exceptions descriptors. It will save you headaches later.