Most of the time, bringing up or shutting down a Unix system is actually very simple. Nevertheless, every system administrator needs to have at least a conceptual understanding of the startup and shutdown processes in order to, at a minimum, recognize situations where something is going awry—and potentially intervene. Providing you with this knowledge is the goal of this chapter. We will begin by examining generic boot and shutdown procedures that illustrate the concepts and features common to virtually every Unix system. This will be followed by sections devoted to the specifics of the various operating systems we are discussing, including a careful consideration of the myriad of system configuration files that perform and control these processes.