0xax/linux-insides

linux-insides is a free, ongoing book about the internal workings of the Linux kernel, the core software that manages hardware resources and runs on every Linux-based system. The book walks readers through what actually happens inside the kernel, starting from the earliest moment a computer boots and progressing through initialization, interrupt handling, system calls, memory management, timers, synchronization, and more. The goal is not to teach Linux usage or system administration, but to explain the actual code and mechanisms inside the kernel itself. Each chapter covers a specific subsystem or concept, for example, how the kernel sets up the CPU and memory during boot, how it manages processes sharing a CPU safely, or how memory is allocated and tracked. The content references the actual kernel source code and explains the data structures, algorithms, and low-level assembly and C code that implement these features. Reading this book requires prior knowledge of the C programming language and some familiarity with assembly language (the low-level instructions that directly control CPU hardware). It is aimed at developers who are curious about operating system internals, kernel contributors, or engineers working on system-level software who want to understand what is happening below the library and application layers. The repository began when the kernel was at version 3.18 and is being updated to reflect modern kernels (v6.18 and later). The "primary language" listed as Python refers to tooling in the repository rather than the book content itself, which covers C and assembly. Community translations exist in Chinese, Japanese, Korean, Russian, Portuguese, Spanish, and Turkish. The book is freely readable on GitHub and is licensed under Creative Commons BY-NC-SA.