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Of possible (mostly historical) interest at this point, a similar commentary on a fairly early version of the original Unix kernel, by an Australian cs prof nam

by rst 8y ago

Of possible (mostly historical) interest at this point, a similar commentary on a fairly early version of the original Unix kernel, by an Australian cs prof named John Lions -- which was very widely circulated among CS students in the '80s, despite this being technically in violation of AT&T's copyright on the book. It's availble online here: http://www.lemis.com/grog/Documentation/Lions/index.php http://www.lemis.com/grog/Documentation/Lions/index.php Note that the code is written in a very archaic dialect of C, and for hardware that didn't support paging in any form (just swapping). Nevertheless, it was an important introduction for a lot of people at the time, not just to the basics of OS implementation details, but also, how to find your way around a nontrivial sized codebase.

dmix 8y ago
There's also the great "The Design of the UNIX Operating System": https://www.amazon.com/Design-UNIX-Operating-System/dp/0132017997/ https://www.amazon.com/Design-UNIX-Operating-System/dp/01320... Which is probably less relevant today in terms of directly understanding the implementation. But an interesting and enlightening read. Things were much simpler and fundamental back in the 1980s. It's easier to understand that way. Then layer on top.
- nicklaf 8y ago
  Slightly more recent: The Design and Implementation of the 4.4 BSD Operating System, which includes some of the Berkeley additions to the kernel, such as TCP/IP and sockets. And then there's xv6 [1], a small Unix running on vx32 from MIT for teaching purposes, full of comments, and available as a booklet that is directly inspired by Lions' commentary on the 6th edition of Unix. I actually agree, though: to really appreciate the classics you should start with (Maurice) Bach. :-P [1] https://pdos.csail.mit.edu/6.828/2018/xv6.html https://pdos.csail.mit.edu/6.828/2018/xv6.html
  - nicklaf 8y ago
    Correction: xv6 runs on QEMU, not vx32 (although Russ Cox co-authored both xv6 and vx32).
yesenadam 8y ago
"Lions' Commentary on UNIX 6th Edition, with Source Code by John Lions (1976) ...Despite its age, it is still considered an excellent commentary on simple but high quality code. For many years, the Lions book was the only Unix kernel documentation available outside Bell Labs. Although the license of 6th Edition allowed classroom use of the source code, the license of 7th Edition specifically excluded such use, so the book spread through illegal copy machine reproductions (a kind of samizdat). It was commonly held to be the most copied book in computer science."[0] I had a look a couple of years ago, it's a joy to read. It's about UNIX on the PDP11. A 1977 version PDF is available here[1] - that page has a cover with endorsement from Ken Thompson and Foreword by Dennis Ritchie, but that seems from a later edition. The end of Lions' preface is funny: "The co-operation of the "nroff" program must also be mentioned. Without it, these notes could never have been produced in this form. However it has yielded some of its more enigmatic secrets so reluctantly that the author's gratitude is indeed mixed. Certainly "nroff" itself must provide a fertile field for future practitioners of the program documenter's art." The Use of these notes section: "These notes, which are intended to supplement the comments already present in the source code, are not essential for understanding the UNIX operating system. It is perfectly possible to proceed without them, and you should attempt to do so as long as you can. The notes are a crutch, to aid you when the going becomes difficult. If you attempt to read each file or procedure on your own first, your initial progress is likely to be slower, but your ultimate progress much faster. Reading other people's programs is an art which should be learnt and practised because it is useful!" The end of the Introduction: "...on the whole you will find that the authors of UNIX, Ken Thompson and Dennis Ritchie, have created a program of great strength, integrity and effectiveness, which you should admire and seek to emulate." [0]https://en.wikipedia.org/wiki/Lions%27_Commentary_on_UNIX_6th_Edition,_with_Source_Code https://en.wikipedia.org/wiki/Lions%27_Commentary_on_UNIX_6t... [1]http://booksdescr.org/item/index.php?md5=6743D838476261CFDEFA3A3A95FA092C http://booksdescr.org/item/index.php?md5=6743D838476261CFDEF...

by rst 8y ago

dmix 8y ago

There's also the great "The Design of the UNIX Operating System": https://www.amazon.com/Design-UNIX-Operating-System/dp/0132017997/ https://www.amazon.com/Design-UNIX-Operating-System/dp/01320... Which is probably less relevant today in terms of directly understanding the implementation. But an interesting and enlightening read. Things were much simpler and fundamental back in the 1980s. It's easier to understand that way. Then layer on top.

nicklaf 8y ago
Slightly more recent: The Design and Implementation of the 4.4 BSD Operating System, which includes some of the Berkeley additions to the kernel, such as TCP/IP and sockets. And then there's xv6 [1], a small Unix running on vx32 from MIT for teaching purposes, full of comments, and available as a booklet that is directly inspired by Lions' commentary on the 6th edition of Unix. I actually agree, though: to really appreciate the classics you should start with (Maurice) Bach. :-P [1] https://pdos.csail.mit.edu/6.828/2018/xv6.html https://pdos.csail.mit.edu/6.828/2018/xv6.html
- nicklaf 8y ago
  Correction: xv6 runs on QEMU, not vx32 (although Russ Cox co-authored both xv6 and vx32).

yesenadam 8y ago

"Lions' Commentary on UNIX 6th Edition, with Source Code by John Lions (1976) ...Despite its age, it is still considered an excellent commentary on simple but high quality code. For many years, the Lions book was the only Unix kernel documentation available outside Bell Labs. Although the license of 6th Edition allowed classroom use of the source code, the license of 7th Edition specifically excluded such use, so the book spread through illegal copy machine reproductions (a kind of samizdat). It was commonly held to be the most copied book in computer science."[0] I had a look a couple of years ago, it's a joy to read. It's about UNIX on the PDP11. A 1977 version PDF is available here[1] - that page has a cover with endorsement from Ken Thompson and Foreword by Dennis Ritchie, but that seems from a later edition. The end of Lions' preface is funny: "The co-operation of the "nroff" program must also be mentioned. Without it, these notes could never have been produced in this form. However it has yielded some of its more enigmatic secrets so reluctantly that the author's gratitude is indeed mixed. Certainly "nroff" itself must provide a fertile field for future practitioners of the program documenter's art." The Use of these notes section: "These notes, which are intended to supplement the comments already present in the source code, are not essential for understanding the UNIX operating system. It is perfectly possible to proceed without them, and you should attempt to do so as long as you can. The notes are a crutch, to aid you when the going becomes difficult. If you attempt to read each file or procedure on your own first, your initial progress is likely to be slower, but your ultimate progress much faster. Reading other people's programs is an art which should be learnt and practised because it is useful!" The end of the Introduction: "...on the whole you will find that the authors of UNIX, Ken Thompson and Dennis Ritchie, have created a program of great strength, integrity and effectiveness, which you should admire and seek to emulate." [0]https://en.wikipedia.org/wiki/Lions%27_Commentary_on_UNIX_6th_Edition,_with_Source_Code https://en.wikipedia.org/wiki/Lions%27_Commentary_on_UNIX_6t... [1]http://booksdescr.org/item/index.php?md5=6743D838476261CFDEFA3A3A95FA092C http://booksdescr.org/item/index.php?md5=6743D838476261CFDEF...