Preface

When I was first approached about converting my experiences with the Linux kernel into a book, I proceeded with trepidation. I did not want to write simply yet another kernel book. Sure, there are not that many books on the subject, but I still wanted my approach to be somehow unique. What would place my book at the top of its subject? I was not motivated unless I could do something special, a best-in-class work.

I then realized that I could offer quite a unique approach to the topic. My job is hacking the kernel. My hobby is hacking the kernel. My love is hacking the kernel. Over the years, I have surely accumulated interesting anecdotes and important tips. With my experiences, I could write a book on how to hack the kernel andmore importantlyhow not to hack the kernel. Primarily, this is a book about the design and implementation of the Linux kernel. The book's approach differs from would-be competition, however, in that the information is given with a slant to learning enough to actually get work doneand getting it done right. I am a pragmatic guy and this is a practical book. It should be fun, easy to read, and useful.

I hope that readers can walk away from this book with a better understanding of the rules (written and unwritten) of the kernel. I hope readers, fresh from reading this book and the kernel source code, can jump in and start writing useful, correct, clean kernel code. Of course, you can read this book just for fun, too.

That was the first edition. Time has passed, and now we return once more to the fray. This edition offers quite a bit over the first: intense polish and revision, updates, and many fresh sections and all new chapters. Changes in the kernel since the first edition have been recognized. More importantly, however, is the decision made by the Linux kernel community^[1] to not proceed with a 2.7 development kernel in the near feature. Instead, kernel developers plan to continue developing and stabilizing 2.6. This implies many things, but one big item of relevance to this book is that there is quite a bit of staying power in a recent book on the 2.6 Linux kernel. If things do not move too quickly, there is a greater chance of a captured snapshot of the kernel remaining relevant long into the future. A book can finally rise up and become the canonical documentation for the kernel. I hope that you are holding that book.

^[1] This decision was made in the summer of 2004 at the annual Linux Kernel Developers Summit in Ottawa, Canada.

Anyhow, here it is. I hope you enjoy it.