Prepare to have you brain melted. This book is FACINATING but not for everyone. It's EXCEEDINGLY nerdy and doesn't attempt to simplify complex nitty gritty details, and it shouldn't. This book is an excelent place to start if you want to dig deeper into the kernel itself. It would be an excelent choice to read before a book on drivers (Linux Device Drivers (Nutshell Handbook)) or low level networking Understanding Linux Network Internals) which are both also very good books.

I would give it 4 stars but it's not quite as well written as some of the other books on Free software published by O'Reilly.

This is a great book to help you understand the linux kernel. It reads easily and helps you to not get lost inside of the details.

If you only read one kernel book, read this one. Also serves as a good general operating system design and implementation primer.

I'm reading this book for fun, and I've been learning so much that I didn't know from Linux, wish our Operating System courses in Venezuela was taught following this book.

To be honest, I am a complete newbie to Linux (more so, the kernel), having only recently shifted to Ubuntu (which, appropriately enough, is often called a "newbie's distribution"). Fortunately, I've had my share of background in C programming both in university and as an employee.

I've only recently delved into the "deeper" side of C - the kind that involves mapping memory and handling register sets to control hardware components. So far as I have read, this book is probably not suitable for the inexperienced, but with a little re-reading, anyone who has the least bit background in computer architecture, operating systems, and, of course, programming can catch up.

"Understanding the Linux Kernel" presents Linux in an abstracted manner, using diagrams whenever possible to illustrate how certain mechanisms - such as, let's say, memory allocation - are executed in the Linux kernel. The presentation, reviewed in line with the Linux kernel code itself, allows the average skilled programmer to obtain at least a basic understanding of Linux and the concept of operating systems in general. In the long run, this material will definitely add to (or completely revolutionize) your repertoire of programming techniques.

Required knowledge to be comfortable with the content are the C syntax, data structures, and an understanding of the binary and hexadecimal number systems.

Understanding the Linux Kernel is an excellent guide for those who have some experience using Linux, and would like to know what's going on under the hood. It's a comprehensive guide that not only describes how Linux boots and initializes itself, and how programs call functions inside the kernel, but actually goes down to the murky depths of interrupts, process switching, inter-process communication, and even memory management down to the level of the 80x86 processor instructions, registers and features (actually if you add it all up, memory management takes up most of the book -- a good thing!). Furthermore there are chapters about essentials such as file systems and device drivers.

The book specifically and explicitly focuses only on the 80x86 PC architecture so if you're interested in Linux on different platforms or if you're looking for a generic Linux kernel book, this one's not for you. Also, if you're just starting out with Linux (whether it be as user, programmer or administrator), there's a lot of information in here that you don't really need to know.

An important part of the kernel that's missing from the book is how networking is implemented. This is understandable, because it would probably require another 900+ pages (that's how thick this one is) to cover in as much detail as what the book DOES cover.

All in all, as an intermediate Linux administrator/user and a novice Linux programmer, I thought this was an excellent addition to my collection, even though I skipped some of the truely low-level parts where the authors go into Pentium registers and stuff like that. The fact that "80x86" is consistently printed as "80 × 86" (notice the multiplication character replacing the letter "x") was not enough of a nuisance to take away any of the 5 stars that I'm giving this one.

Are you curious about how Linux works and why it is so efficient? If you are, then this book is for you! Authors Daniel Plerre Bovet and Marco Cesati, have done an outstanding job of writing a practical book that will help you find your way through the many thousands of lines of code.

Bovet and Cesati, begin by presenting a general picture of what is inside a Unix kernal and how Linux competes against other well-known Unix systems. Then, the authors explain how 80x86 processors include special circuits to address data in memory and how Linux exploits them. They continue by explaining how each process runs either in an unprivileged User Mode or in a privileged Kernal Mode. Then, the authors introduce interrupts and exceptions. Then, they discuss how synchronization mechanisms are needed so that all these requests can be serviced in a interleaved way by the kernal. Next, the authors discuss timing measurements. Then, they explain how Linux executes, in turn, every active process in the system so that all of them can progress toward their completions. They continue by describing the sophisticated techniques required to handle the most precious resource in the system. Next, the authors show you how the kernal copes with the requests for memory issued by greedy application programs. Then, they explain how a process running in User Mode makes requests to the kernal. They continue by describing how a process may send synchronization signals to other processes. Then, the authors introduce a general layer that supports many different filesystems. Next, they offer insights into special files and on the corresponding hardware device drivers. They also show you how to reduce disk accesses through the use of RAM. Then, they show you how user applications access normal files. Next, the authors explain the techniques used by Linux to ensure that enough memory is always available. Then, they illustrate the most frequently used Linux filesystem, namely Ext2 and its recent evolution, Ext3. They continue by introducing communication mechanisms other than signals available to User Mode processes. Finally, the authors explain how user applications are started.

This most excellent book helps you distinguish between crucial data structures and secondary ones. More importantly, this book helps you become a true Linux hacker.

Very good book. I would like to see more coverage of SMP
support.

One thing that's really missing is a nice chapter on Kernel debugging -- using some existing kernel debuggers and how they all compare, interpreting those OOPS messages -- everything that goes with kernel hacking!
This book covers VMM so comprehensively that it's really meant for those who _actually_ want to work on kernel, so a 'Kernel Hacking' chapter was a must.

Otherwise this book is just perfect - I give it 5 stars :)

The book "Undestanding the Linux Kernel",
explains clearly the inner workings of the
current 2.6 Linux kernel.
The presentation is at a considerable level of detail,
the authors fully describe the important data structures,
and the significant chunks of code.
The book is indispensable to any serious
Linux kernel developer.

However, it can be used also at the context
of an "Operating Systems Design" academic course
and the students can learn a lot from the
technologically advanced Linux 2.6 kernel implementation
and can modify/recompile and install their own version!

The level of the book is advanced and I recommend
concurrently with it, the reader to study also the
book:
"Linux kernel development" by Robert Love
that presents the algorithms also very clearly,
but with a more academic view,
without zooming to all the implementation concerns.

I own both books and by studing them, I can have
the significant experience of customizing the source code
of the superior Linux 2.6 kernel.

A true classic. A must buy if you want to understand the working of the linux kernel in an "easy to understand" manner...

Charlie Black complained (on December 2nd) that inotify was not in the index of this kernel book. Sorry, books take time to publish. inotify was not in the kernel till version 2.6.13, which was just 3 months before the book was published and available.

Linux kernel development is a moving target and it takes more than a few months to publish any book, let alone one of this magnitude.

I am just purchasing this book. I have found version 1 and 2 invaluable. The kernel is huge and the other versions have done an excelent job of covering as much as possible in one book.

If you are interested in inotify, then you can do a web search and find the introductory article written by Robert Love in LJ.

I was browsing the index for the new edition and lots of topics fail to appear. One I was especially interested is inotify. Kinda odd that it doesn't make the index.

PHPTR has also put out some kernel books and they were disappointing.

The third edition of this valuable resource incorporates descriptions of the latest changes in the 2.6 Linux kernel series. There is simply nothing else out there resembling this work in either depth or breadth, and as such every developer active in Linux kernel work (or trying to understand how it all fits together) needs to have this book.

While there are a few other books out there that describe the Linux kernel on a conceptual level (a very few of which have quality), there is really nothing (recently) that examines the actual code at this level of detail (each edition keeps getting fatter.)

As academics the authors are interested in presenting a complete snapshot of the Linux kernel, and unravelling how it works. This is unlike in method (but complementary to) the engineer's approach of its excellent companion book from O'Reilly, Linux Device Drivers, by Corbet, Rubini and Kroah-Hartmann. They also focus more on the x86 architecture in order to be definite. Because of its focus on being an entire picture, understanding this book doesn't require extensive pre-knowledge of the Linux kernel, only a good general grasp of principles.

I have used the earlier editions as companion textbooks for classes on the Linux kernel, and intend on using this edition in the same fashion. Don't miss out on this unique book.