One of the first obstacles in discussing the theory of system administration is defining its scope. System administrators are called upon to perform all manner of tasks as part of their duties. This battery of skills has no particular cohesion or structure to it, so it resists formalization. We must improve on this situation if we are to make progress in forming a theory of system administration. In particular, we must restrict its scope to encompass only core activities. These core activities will include insuring availability, efficiency, and security for all users, and finally fault diagnosis of the system. This includes issues such as software installation and upgrades, which can be classified under availability and efficiency. It also includes user management to a certain extent, though it will not be useful to address the issue of creation of user accounts in this context.