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This chapter considers the sequence of events which occur when UNIX is “rebooted” i.e. it is loaded and initiated in an idle machine.
A study of the initialisation process is of interest in itself, but more importantly, it allows a number of important features of the system to be presented in an orderly manner.
The operating system may have to be restarted in the aftermath of a system crash. It will also have to be restarted frequently for quite ordinary, operational reasons, e.g. after an overnight shutdown. If we assume the latter case, then we can assume that all the disk files are intact and that no special circumstance needs to be recognised or dealt with.
In particular, we can assume there is a file in the root directory called “/unix”, which is the object code for the operating system.
This file began life as a set of source files such as we are investigating. These were compiled and linked together in the normal way to form a single object program file, and stored in the root directory.
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