Setting up my bike for commuting so I figured I'd equipe my rack pack with the essentials, including a slick little multi-tool I got on sale. This tool includes a device for removing and installing chain links. So this brings up the question; should I be prepared to repair my chain on the road? How often does a chain break? What would I need to carry to do this, besides the tool? Extra links? Extra chunk of chain? Spare whole chain? If I do need to do a roadside repair, how easy is this to do?

Thanks