The Design and Implementation of the FreeBSD Operating System

First of all you should be warned that this is not an introduction to get started with UNIX kernel programming. The Design of the UNIX Operating System by M.J. Bach provides a good general introduction to UNIX kernel programming. The design and implementation of the FreeBSD operating system is an excellent book to deepen knowledge of the UNIX kernel by looking how a current UNIX is implemented in practice. Even if you plan to write code for another kernel, working through the FreeBSD kernel with this book as a guide is a good excercise to become consious of the fundamental problems and solutions in kernel design. FreeBSD (or any of the other BSDs) is a good starting point, because the BSDs have relatively stable kernel subsystems and APIs due to the long cycles in BSD development. The writing style of the authors is to the point (don't expect a novel) and clear. The troff typesetting of the book gives it a consistent style and simple, but clear diagrams (though I heard that some diagrams were hand-drawn). The book doesn't just drop the reader in a kernel subsystem. The second chapter gives a detailed explanation of the various kernel subsystems, and the relation between the subsystems. The third chapter gives a summary of what is expected from a kernel from the user level. Combined these two chapters give the reader the necessary conception of the FreeBSD kernel to start looking at individual parts of the kernel in detail. Most remaining chapters are logically ordered, in that subsystems are ordered from parts with less dependencies to parts with more dependencies (e.g. memory management and I/O are covered before filesystems). If you are interested in UNIX programming, you should have this book on your bookshelf (as well as a CVS checkout of the FreeBSD kernel tree to read the implementation).

The Design And Implementation Of The FreeBSD Operating System is the collaborative work of computer science and UNIX operating systems experts Marshal Kirk McKusick and George V. Neville-Neil. Covering FreeBSD version 5.2, this is an advanced resource especially for advanced students and users of the widely used FreeBSD system, which is commonly applied to Internet services and firewalls, high-availability servers, general timesharing systems, embedded systems that take advantage of FreeBSD's lean qualities, and much more. Chapters include an overview of FreeBSD's history, goals, and general design, and then delve into the nuts and bolts of its kernel services, process management, i/o system, network filesystem, network protocols, and much more. A complex and technical reference featuring diagrams and flowcharts summarizing how FreeBSD operates, The Design And Implementation Of The FreeBSD Operating System is a "must-have" in-depth work for anyone concerned with learning the capabilities, most efficient interfaces, fine-tuning configurements, and more details of FreeBSD.

I have been administering FreeBSD systems for four years, and I read 'The Design' to get a better understanding of the system 'under the hood.' This book is definitely not for beginners, and intermediate users like myself can become quickly overwhelmed. Nevertheless, I am very glad FreeBSD developers like McKusick and Neville-Neil took the time to document the kernel in this book. Before tackling 'The Design,' I recommend reading a book like 'Modern Operating Systems, 2nd Ed' by Andrew Tannenbaum. The reader needs to be familiar with OS concepts and terms like 'mutex,' 'semaphore,' 'locking,' and so on before reading 'The Design.' If for some reason you want to read 'The Design' but are not familiar with userland FreeBSD issues, I recommend Greg Lehey's 'Complete FreeBSD, 4th Ed.' I was unable to grasp all of the material in 'The Design,' since some of it will appeal only to those coding their own kernels or who are equipped to debate the FreeBSD core team's design choices. In that respect the book is well suited for a college course (perhaps a master's level?) where the content could be discussed by a professor and students. I was able to critically read the chapters covering networking (ch. 11-13) as I deploy FreeBSD partly for its robust TCP/IP stack. Reading 'The Design' helped me understand some of Robert Watson's recent posts concerning removal of the GIANT lock from the networking subsystem, for example. There are many other parts of the book which non-kernel developers will find accessible. Nearly every chapter features a well-written introduction to the technology at hand, such as memory management (ch. 5) or devices (ch. 7). I found various bits of history helpful, like the development of NFS (ch. 9) or UNIX itself (ch. 1). Those trying to understand issues concerning the new ULE scheduler will find ch. 4 enlightening. The 38 page glossary is also excellent and the index is well-constructed. 'The Design' is the sort of book I expect to consult when I need greater insight to a certain aspect of the FreeBSD kernel. It's an excellent companion when one reads the freebsd-current mailing lists and needs background on the latest hot design issue. I would be happy to see other operating systems have similar books published, so that an apples-to-apples comparison of their capabilities could be made by informed users.

This hardback academic style book is an impressive piece of work. The writing style is serious, but not overwhelming, and the use of graphics is appropriate and effective. The organization is what you would expect, it cuts the Kernel as if it were an onion and starts at the center, covering I/O and devices, goes through process management, file systems, IPC and networking. There are exercises at the end of every chapter. This book is a genuinely impressive piece of work. It's well worth the money for anyone looking for a computer science work on operating systems construction.

For some 15 years or more, Addison-Wesley has published a set of definitive books on Unix, C and the Internet. It is a pleasure to see that this FreeBSD book continues that tradition. The book goes into a detailed explanation of FreeBSD's kernel and associated matters. Strictly for the experienced unix programmer or systems developer. At the core of the kernel are many algorithms. It is these and their data structures that are the essence of this book. Also worthy of mention is the inclusion of exercises at the end of each chapter. Given that we have an algorithms book, the subject lends itself readily to probing questions, and it is nice that the authors chose to do so. We also have a discussion of FreeBSD versus linux. In recent years, linux has grown hugely, and has overtaken FreeBSD. The authors face this issue squarely. That is, if you are choosing a unix to develop on, why pick FreeBSD? The main point is that for anything you make under it, you do not have to fold back into the main FreeBSD thread, by revealing or relinquishing the source code or any other intellectual property.