Understanding Linux

The book "Understanding Linux: The Kernel Perspective" is a guided, practical exploration of how the kernel operates-without getting lost in the full-scale kernel development. The Linux kernel is highly efficient but deliberately hidden from casual users, making it easy to overlook, and we focus on what matters most for conceptual clarity and practical insight. You will learn how to build and insert loadable kernel modules-small, self-contained units of kernel code-into a running system. These modules are central to a series of hands-on exercises that reveal how core kernel features work in practice. The book cover the topics such as:

• Unix shells - including how bash executes commands.

• Processes - including how the kernel starts user space, what ELF binaries are, and how processes are tracked through kernel data structures.

• System calls - how user programs invoke kernel services, with examples like execve() and fork().

• Memory management - including virtual memory, memory mappings, and the kernel's view of memory layout.

• Filesystems - covering inodes, mounting, pseudo-filesystems like procfs, and interaction with block devices.

• Networking - examining how the kernel handles packets, protocols, and connection tracking via the Netfilter framework.

Exercises include analysing ELF headers, listing virtual memory areas (VMAs), creating custom procfs entries, and inspecting TCP/UDP network packets. If you're an intermediate Linux user aiming to become an expert with a deep understanding of how Linux works, this book is for you. While the book follows a logical progression, each section is self-contained and can be read independently, making it easy to jump to topics of interest without prior chapters. The code presented in the book is available or download (instructions provided within the book). Covers Linux Kernel 6.x.

This edition now includes an audio companion. It provides abridged chapter summaries and selected Linux topics designed to reinforce understanding and support learning while away from the terminal.