Abstract: The fact that systems fail should come as no surprise to anymore who has ever developed or worked on a system. A failure reduces the availability of the system and hence the productivity of entities using this system. To increase system availability, several approaches have been developed; these approaches range from simple techniques such as restarting the entire system, to complex algorithms that isolate and restart the failed subsystem. We find the simple approach of a system reboot to be particularly interesting because it is a widely deployed approach. We profile the set of instructions excuted during the startup phase of the system and identify heavily utilized segments. We implement, in Xen, a framework for both monitoring the start-up sequence and identifying highly utilized segments of code. We show that modifications to the identified segments affect the start-up sequence. Finally, we examine the identified segments and suggest modifications that will, if implemented, increase availability by reducing the boot up time.