Main tasks of system administration are described, basic protocols are described, recommendations on equipment selection and daily routine operations are given. Technologies used in building information systems are described in detail, means of monitoring and servicing both small and distributed networks are described. Methods of centralized management, fundamentals of creating a safe environment are considered. Recommendations for troubleshooting, data protection are given. At the same time, solutions based on Windows operating systems (including Windows 78 and Windows Server 2012) and Linux using both proprietary and open technologies were considered. The book is written on the basis of many years of experience in the development and practical administration of information systems.