Groklaw – Andrew S. Tanenbaum’s Reply to ADTI

Groklaw – Andrew S. Tanenbaum’s Reply to ADTI


On 20 May 2004, I posted a statement refuting the claim of Ken Brown, President of the Alexis de Tocqueville Institution, that Linus Torvalds didn’t write Linux. My statement was mentioned on Slashdot, Groklaw, and many other Internet news sites. This attention resulted in over 150,000 requests to our server in less than a day, which is still standing despite yesterday being a national holiday with no one there to stand next to it saying “You can do it. You can do it.” Kudos to Sun Microsystems and the folks who built Apache. My statement was mirrored all over the Internet, so the number of true hits to it is probably a substantial multiple of that. There were also quite a few comments at Slashdot, Groklaw, and other sites, many of them about me. I had never engaged in remote multishrink psychoanalysis on this scale before, so it was a fascinating experience.

The Brown Book

I got an advance copy of Ken Brown’s book. I think it is still under embargo, so I won’t comment on it. Although I am not an investigative reporter, even I know it is unethical to discuss publications still under embargo. Some of us take ethics more seriously than others. So I won’t even reveal the title. Let’s call it The Brown Book. There is some precedent for nicknaming books after colors: The International Standard for the CD-ROM (IS 10149) is usually called The Red Book.

Suffice it to say, there is a great deal to criticize in the book. I am sure that will happen when it is published. I may even help out.

Brown’s Motivation

What prompted me to write this note today is an email I got yesterday. Actually, I got quite a few šŸ™‚ , most of them thanking me for the historical material. One of yesterday’s emails was from Linus, in response to an email from me apologizing for not letting him see my statement in advance. As a matter of courtesy, I did try but I was using his old address and didn’t know his new one until I got a very kind email from Linus’ father, a Finnish journalist.

In his email, Linus said that Brown never contacted him. No email, no phone call, no personal interview. Nothing. Considering the fact that Brown was writing an explosive book in which he accused Linus of not being the author of Linux, you would think a serious author would at least confront the subject with the accusation and give him a chance to respond. What kind of a reporter talks to people on the periphery of the subject but fails to talk to the main player?

Why did Brown fly all the way to Europe to interview me and (and according to an email I got from his seat-mate on the plane) one other person in Scandinavia, at considerable expense, and not at least call Linus? Even if he made a really bad choice of phone company, how much could that cost? Maybe a dollar? I call the U.S. all the time from Amsterdam. It is less than 5 cents a minute. How much could it cost to call California from D.C.?

From reading all the comments posted yesterday, I am now beginning to get the picture. Apparently a lot of people (still) think that I ‘hate’ Linus for stealing all my glory (see below for more on this). I didn’t realize this view was so widespread. I now suspect that Brown believed this, too, and thought that I would be happy to dump all over Linus to get ‘revenge.’ By flying to Amsterdam he thought he could dig up dirt on Linus and get me to speak evil of him. He thought I would back up his crazy claim that Linus stole Linux from me. Brown was wrong on two counts. First, I bear no ‘grudge’ against Linus at all. He wrote Linux himself and deserves the credit. Second, I am really not a mean person. Even if I were still angry with him after all these years, I wouldn’t choose some sleazy author with a hidden agenda as my vehicle. My home page gets 2500 hits a week. If I had something to say, I could put it there.

When The Brown Book comes out, there will no doubt be a lot of publicity in the mainstream media. Any of you with contacts in the media are actively encouraged to point reporters to this page and my original statement to provide some balance. I really think Brown’s motivation should come under scrutiny. I don’t believe for a nanosecond that Brown was trying to do a legitimate study of IP and open source or anything like that. I think he was trying to make the case the people funding him (which he refused to disclose to me despite my asking point blank) wanted to have made. Having an institution with an illustrious-sounding name make the case looks better than having an interested party make the case.

Clearing Up Some Misconceptions

I would like to close by clearing up a few misconceptions and also correcting a couple of errors. First, I REALLY am not angry with Linus. HONEST. He’s not angry with me either. I am not some kind of “sore loser” who feels he has been eclipsed by Linus. MINIX was only a kind of fun hobby for me. I am a professor. I teach and do research and write books and go to conferences and do things professors do. I like my job and my students and my university. If you want to get a masters there, see my home page for information. I wrote MINIX because I wanted my students to have hands-on experience playing with an operating system. After AT&T forbid teaching from John Lions book, I decided to write a UNIX-like system for my students to play with. Since I had already written two books at this point, one on computer architecture and one on computer networks, it seemed reasonable to describe the system in a new book on operating systems, which is what I did. I was not trying to replace GNU/HURD or Berkeley UNIX. Heaven knows, I have said this enough times. I just wanted to show my students and other students how you could write a UNIX-like system using modern technology. A lot of other people wanted a free production UNIX with lots of bells and whistles and wanted to convert MINIX into that. I was dragged along in the maelstrom for a while, but when Linux came along, I was actually relieved that I could go back to professoring. I never really applied for the position of King of the Hackers and didn’t want the job when it was offered. Linus seems to be doing excellent work and I wish him much success in the future.

While writing MINIX was fun, I don’t really regard it as the most important thing I have ever done. It was more of a distraction than anything else. The most important thing I have done is produce a number of incredibly good students, especially Ph.D. students. See my home page for the list. They have done great things. I am as proud as a mother hen. To the extent that Linus can be counted as my student, I’m proud of him, too. Professors like it when their students go on to greater glory. I have also written over 100 published research papers and 14 books which have been translated into about 20 languages. As a result I have become a Fellow of the IEEE, a Fellow of the ACM, and won numerous other awards. For me, these are the things that really count. If MINIX had become a big ‘commercial’ success I wouldn’t have had the time to do all this academic stuff that I am actually more interested in.

Microkernels Revisited

I can’t resist saying a few words about microkernels. A microkernel is a very small kernel. If the file system runs inside the kernel, it is NOT a microkernel. The microkernel should handle low-level process management, scheduling, interprocess communication, interrupt handling, and the basics of memory management and little else. The core microkernel of MINIX 1.0 was under 1400 lines of C and assembler. To that you have to add the headers and device drivers, but the totality of everything that ran in kernel mode was under 5000 lines. Microsoft claimed that Windows NT 3.51 was a microkernel. It wasn’t. It wasn’t even close. Even they dropped the claim with NT 4.0. Some microkernels have been quite successful, such as QNX and L4. I can’t for the life of me see why people object to the 20% performance hit a microkernel might give you when they program in languages like Java and Perl where you often get a factor 20x performance hit. What’s the big deal about turning a 3.0 GHz PC into a 2.4 GHz PC due to a microkernel? Surely you once bought a machine appreciably slower than 2.4 GHz and were very happy with it. I would easily give up 20% in performance for a system that was robust, reliable, and wasn’t susceptible to many of the ills we see in today’s massive operating systems.


I would now like to correct an error in my original statement. One of the emails I got yesterday clarified the origins of Coherent. It was not written by Bob Swartz. He was CEO of the Mark Williams Company. Three ex-students from the University of Waterloo, Dave Conroy, Randell Howard, and Johann George, did most of the work. Waterloo is in Canada, where they also play baseball I am told, but only after the ice melts and they can’t play hockey. It took the Waterloo students something like 6 man-years to produce Coherent, but this included the kernel, the C compiler, the shell, and ALL the utilities. The kernel is only a tiny fraction of the total code, so it may well be that the kernel itself took a man year. It took me three years to write MINIX, but I was only working at it only in the evenings, and I also wrote 400 pages of text describing the code in that time period (also in the evenings). I think a good programmer can write a 12,000 line kernel in a year.

If you have made it this far, thank you for your time. Permission is hereby granted to mirror this web page provided that the original, unmodified version is used.

Andy Tanenbaum, 21 May 2004


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