The main tasks of system administration are outlined, basic protocols are described, and recommendations are given for choosing equipment and carrying out daily routine operations. The technologies used in the construction of information systems are described in detail, and the means for monitoring and maintaining both small and distributed networks are described. Methods of centralized management and the basics of creating a safe environment are considered. Recommendations are given for troubleshooting and ensuring data protection. In parallel, solutions based on the Windows and Linux operating systems using both proprietary and open technologies are considered. The book is written on the basis of many years of experience in the development and practical administration of information systems. The fifth edition examines the latest technologies, including Windows 10 and Windows Server 2016. Particular attention is paid to cloud technologies, including issues of choosing a cloud provider, creating a virtual server for 1C and etc., the number of practical tips, instructions and recommendations has increased significantly.