This open access book covers operating system fundamentals, UNIX/Linux design philosophy, and openEuler practices. It introduces basic OS knowledge, openEuler usage, OS principles, Linux development, embedded OS development, network fundamentals, server system management, and openEuler's open source innovations. It delves into Linux development and application, comparing it to UNIX design. Practical cases from the openEuler platform enhance understanding and facilitate modern Linux application. For beginners, it quickly builds Linux proficiency and system management skills. For experts, it offers new insights into Linux operational logic, aiding efficient tool use and inspiring software architecture design. Suitable for computer science, automation, and electronic measurement students, it's also valuable for Linux developers and computer professionals.