The study of operating systems is a fundamental component of all undergraduate computer science degree programmes. Making operating system concepts concrete typically entails large programming projects. Such projects traditionally involve enhancing an existing module in a real-world operating system or extending a pedagogical operating system. The latter programming projects represent the gold standard in the teaching of operating systems and their value is undoubted. However, there is room in introductory operating systems courses for supplementary approaches and tools that support the demonstration of operating system concepts in the context of a live, real-world operating system. This paper describes an approach where the Linux monitoring tool SystemTap is used to capture kernel-level events in order to illustrate, with concrete examples, operating system concepts in the areas of scheduling, file system implementation and memory management. For instructors and students (where often for the latter seeing is believing) this approach offers an additional simple and valuable resource for solidifying understanding of concepts that might otherwise remain purely theoretical.