* Crossposted in Linux
Hello All.

For those who follow the SCO/MS/Linux saga, the latest is that the by now
(in)famous Alexis de Tocqueville Institution (paid by Microsoft) continues
its FUD spreading by rewriting history. Linus is not the father of Linux
(according to them). Linus himself acknoledged that he was a front man for
both Santa Claus AND the tooth fairy. Here is what professor Tanebaum has
to say about it:

(http://www.cs.vu.nl/~ast/brown)

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Some Notes on the "Who wrote Linux" Kerfuffle, Release 1.3
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Background

The history of UNIX and its various children and grandchildren has
been in the news recently as a result of a book from the Alexis de
Tocqueville Institution. Since I was involved in part of this history,
I feel I have an obligation to set the record straight and correct some
extremely serious errors. But first some background information.

Ken Brown, President of the Alexis de Tocqueville Institution, contacted
me in early March. He said he was writing a book on the history of UNIX
and would like to interview me. Since I have written 15 books and have
been involved in the history of UNIX in several ways, I said I was
willing to help out. I have been interviewed by many people for many
reasons over the years, and have been on Dutch and US TV and radio and
in various newspapers and magazines, so I didn't think too much about it.

Brown flew over to Amsterdam to interview me on 23 March 2004. Apparently
I was the only reason for his coming to Europe. The interview got off
to a shaky start, roughly paraphrased as follows:

AST: "What's the Alexis de Tocqueville Institution?"
KB: We do public policy work
AST: A think tank, like the Rand Corporation?
KB: Sort of
AST: What does it do?
KB: Issue reports and books
AST: Who funds it?
KB: We have multiple funding sources
AST: Is SCO one of them? Is this about the SCO lawsuit?
KB: We have multiple funding sources
AST: Is Microsoft one of them?
KB: We have multiple funding sources

He was extremely evasive about why he was there and who was funding
him. He just kept saying he was just writing a book about the history
of UNIX. I asked him what he thought of Peter Salus' book, A Quarter
Century of UNIX. He'd never heard of it! I mean, if you are writing a
book on the history of UNIX and flying 3000 miles to interview some guy
about the subject, wouldn't it make sense to at least go to amazon.com
and type "history unix" in the search box, in which case Salus' book is
the first hit? For $28 (and free shipping if you play your cards right)
you could learn an awful lot about the material and not get any jet
lag. As I soon learned, Brown is not the sharpest knife in the drawer,
but I was already suspicious. As a long-time author, I know it makes
sense to at least be aware of what the competition is. He didn't bother.

UNIX and Me

I didn't think it odd that Brown would want to interview me about the
history of UNIX. There are worse people to ask. In the late 1970s and
early 1980s, I spent several summers in the UNIX group (Dept. 1127)
at Bell Labs. I knew Ken Thompson, Dennis Ritchie, and the rest of the
people involved in the development of UNIX. I have stayed at Rob Pike's
house and Al Aho's house for extended periods of time. Dennis Ritchie,
Steve Johnson, and Peter Weinberger, among others have stayed at my
house in Amsterdam. Three of my Ph.D. students have worked in the UNIX
group at Bell Labs and one of them is a permanent staff member now.

Oddly enough, when I was at Bell Labs, my interest was not operating
systems, although I had written one and published a paper about it
(see "Software - Practice & Experience," vol. 2, pp. 109-119, 1973). My
interest then was compilers, since I was the chief designer of the the
Amsterdam Compiler Kit (see Commun. of the ACM, vol. 26, pp. 654-660,
Sept. 1983.). I spent some time there discussing compilers with Steve
Johnson, networking with Greg Chesson, writing tools with Lorinda Cherry,
and book authoring with Brian Kernighan, among many others. I also
became friends with the other "foreigner," there, Bjarne Stroustrup,
who would later go on to design and implement C++.

In short, although I had nothing to do with the development of the
original UNIX, I knew all the people involved and much of the history
quite well. Furthermore, my contact with the UNIX group at Bell Labs was
not a secret; I even thanked them all for having me as a summer visitor in
the preface to the first edition of my book Computer Networks. Amazingly,
Brown knew nothing about any of this. He didn't do his homework before
embarking on his little project

MINIX and Me

Years later, I was teaching a course on operating systems and using John
Lions' book on UNIX Version 6. When AT&T decided to forbid the teaching
of the UNIX internals, I decided to write my own version of UNIX, free of
all AT&T code and restrictions, so I could teach from it. My inspiration
was not my time at Bell Labs, although the knowledge that one person could
write a UNIX-like operating system (Ken Thompson wrote UNICS on a PDP-7)
told me it could be done. My real inspiration was an off-hand remark
by Butler Lampson in an operating systems course I took from him when
I was a Ph.D. student at Berkeley. Lampson had just finished describing
the pioneering CTSS operating system and said, in his inimitable way: "Is
there anybody here who couldn't write CTSS in a month?" Nobody raised his
hand. I concluded that you'd have to be real dumb not to be able to write
an operating system in a month. The paper cited above is an operating
system I wrote at Berkeley with the help of Bill Benson.  It took a lot
more than a month, but I am not as smart as Butler. Nobody is.

I set out to write a minimal UNIX clone, MINIX, and did it alone. The code
was 100% free of AT&T's intellectual property. The full source code was
published in 1987 as the appendix to a book, Operating Systems: Design and
Implementation, which later went into a second edition co-authored with
Al Woodhull. MINIX 2.0 was even POSIX-conformant. Both editions contained
hundreds of pages of text describing the code in great detail. A box of
10 floppy disks containing all the binaries and source code was available
separately from Prentice Hall for $69.

While this not free software in the sense of "free beer" it was free
software in the sense of "free speech" since all the source code was
available for only slightly more than the manufacturing cost. But even
"free speech" is not completely "free"--think about
slander, yelling
"fire" in a crowded theater, etc. And this was before the Patriot Act,
which requires John Ashcroft's written permission before you can open your
mouth. Also Remember (if you are old enough) that by 1987, a university
educational license for UNIX cost $300, a commercial license for a
university cost $28,000, and a commercial license for a company cost
a lot more. For the first time, MINIX brought the cost of "UNIX-like"
source code down to something a student could afford. Prentice Hall
wasn't really interested in selling software. They were interested in
selling books, so there was a fairly liberal policy on copying MINIX,
but if a company wanted to sell it to make big bucks, PH wanted a royalty.
Hence the PH lawyers equipped MINIX with a lot of boilerplate, but there
was never any intention of really enforcing this against universities
or students. Using the Internet for distributing that much code was not
feasible in 1987, even for people with a high-speed (i.e., 1200 bps)
modem. When distribution via the Internet became feasible, I convinced
Prentice Hall to drop its (extremely modest) commercial ambitions and they
gave me permission to put the source on my website for free downloading,
where it still is.

Within a couple of months of its release, MINIX became something of a
cult item, with its own USENET newsgroup, comp.os.minix, with 40,000
subscribers. Many people added new utility programs and improved the
kernel in numerous ways, but the original kernel was just the work of
one person--me. Many people started pestering me about improving it. In
addition to the many messages in the USENET newsgroup, I was getting
200 e-mails a day (at a time when only the chosen few had e-mail at all)
saying things like: "I need pseudoterminals and I need them by Friday." My
answer was generally quick and to the point: "No."

The reason for my frequent "no" was that everyone was trying to turn
MINIX into a production-quality UNIX system and I didn't want it to get
so complicated that it would become useless for my purpose, namely,
teaching it to students. I also expected that the niche for a free
production-quality UNIX system would be filled by either GNU or Berkeley
UNIX shortly, so I wasn't really aiming at that. As it turned out, the
GNU OS sort of went nowhere (although many UNIX utilities were written)
and Berkeley UNIX got tied up in a lawsuit when its designers formed a
company, BSDI, to sell it and they chose 1-800-ITS UNIX as their phone
number. AT&T felt this constituted copyright infringement and sued
them. It took a couple of years for this to get resolved. This delay
in getting free BSD out there gave Linux the breathing space it needed
to catch on. If it hadn't been for the lawsuit, undoubtedly BSD would
have filled the niche for a powerful, free UNIX clone as it was already
a stable, mature system with a large following.

Ken Brown and Me

Now Ken Brown shows up and begins asking questions. I quickly determined
that he didn't know a thing about the history of UNIX, had never heard
of the Salus book, and knew nothing about BSD and the AT&T lawsuit. I
started to tell him the history, but he stopped me and said he was
more interested in the legal aspects. I said: "Oh you mean about Dennis
Ritchie's patent number 4135240 on the setuid bit?" Then I added:"That's
not a problem. Bell Labs dedicated the patent." That's when I discovered
that (1) he had never heard of the patent, (2) did not know what it meant
to dedicate a patent (i.e., put it in the public domain), and (3) really
did not know a thing about intellectual property law. He was confused
about patents, copyrights, and trademarks. Gratuitously, I asked if he
was a lawyer, but it was obvious he was not and he admitted it. At this
point I was still thinking he might be a spy from SCO, but if he was,
SCO was not getting its money's worth.

He wanted to go on about the ownership issue, but he was also trying
to avoid telling me what his real purpose was, so he didn't phrase
his questions very well. Finally he asked me if I thought Linus wrote
Linux. I said that to the best of my knowledge, Linus wrote the whole
kernel himself, but after it was released, other people began improving
the kernel, which was very primitive initially, and adding new software
to the system--essentially the same development model as MINIX. Then he
began to focus on this, with questions like: "Didn't he steal pieces of
MINIX without permission." I told him that MINIX had clearly had a huge
influence on Linux in many ways, from the layout of the file system to
the names in the source tree, but I didn't think Linus had used any of
my code. Linus also used MINIX as his development platform initially,
but there was nothing wrong with that. He asked if I objected to that
and I said no, I didn't, people were free to use it as they wished for
noncommercial purposes. Later MINIX was released under the Berkeley
license, which freed it up for all purposes. It is still in surprisingly
wide use, both for education and in the Third World, where millions of
people are happy as a clam to have an old castoff 1-MB 386, on which
MINIX runs just fine. The MINIX home page cited above still gets more
than 1000 hits a week.

Finally, Brown began to focus sharply. He kept asking, in different forms,
how one person could write an operating system all by himself. He simply
didn't believe that was possible. So I had to give him more history,
sigh. To start with, Ken Thompson wrote UNICS for the PDP-7 all by
himself. When it was later moved to the PDP-11 and rewritten in C,
Dennis Ritchie joined the team, but primarily focused on designing the C
language, writing the C compiler, and writing the I/O system and device
drivers. Ken wrote nearly all of the kernel himself.

In 1983, a now-defunct company named the Mark Williams company produced
and sold a very good UNIX clone called Coherent. Most of the work was
done by Bob Swartz. I used this system for a while and it was very solid.

In 1983, Rick Holt published a book, now out of print, on the TUNIS
system, a UNIX-like system. This was certainly a rewrite since TUNIS
was written in a completely new language, concurrent Euclid.

Then Doug Comer wrote XINU. While also not a UNIX clone, it was a
comparable system.

By the time Linus started, five people had independently implemented the
UNIX kernel or something approximating it, namely, Thompson, Swartz,
Holt, Comer, and me. All of this was perfectly legal and nobody stole
anything. Given this history, it is pretty hard to make a case that
one person can't implement a system of the complexity of Linux, whose
original size was about the same as V1.0 of MINIX.

Of course it is always true in science that people build upon the work of
their predecessors. Even Ken Thompson wasn't the first. Before writing
UNIX, Ken had worked on the MIT MULTICS (MULTiplexed Information and
Computing Service) system. In fact, the original name of UNIX was UNICS,
a joke made by Brian Kernighan standing for the UNIplexed Information
and Computing Service, since the PDP-7 version could support only one
user--Ken. After too many bad puns about EUNUCHS being a castrated
MULTICS, the name was changed to UNIX. But even MULTICS wasn't
first. Before it was the above-mentioned CTSS, designed by the same team
at MIT.

Thus, of course, Linus didn't sit down in a vacuum and suddenly type in
the Linux source code. He had my book, was running MINIX, and undoubtedly
knew the history (since it is in my book). But the code was his. The
proof of this is that he messed the design up. MINIX is a nice, modular
microkernel system, with the memory manager and file system running as
user-space processes. This makes the system cleaner and more reliable
than a big monolithic kernel and easier to debug and maintain, at a small
price in performance, although even on a 4.77 MHz 8088 it booted in maybe
5 seconds (vs. a minute for Windows on hardware 500 times faster). An
example of commercially successful microkernel is QNX. Instead of writing
a new file system and a new memory manager, which would have been easy,
Linus rewrote the whole thing as a big monolithic kernel, complete with
inline assembly code :-( . The first version of Linux was like a time
machine. It went back to a system worse than what he already had on his
desk. Of course, he was just a kid and didn't know better (although if
he had paid better attention in class he should have), but producing a
system that was fundamentally different from the base he started with
seems pretty good proof that it was a redesign. I don't think he could
have copied UNIX because he didn't have access to the UNIX source code,
except maybe John Lions' book, which is about an earlier version of UNIX
that does not resemble Linux so much.

My conclusion is that Ken Brown doesn't have a clue what he is talking
about. I also have grave questions about his methodology. After he talked
to me, he prowled the university halls buttonholing random students and
asking them questions.  Not exactly primary sources.

The six people I know of who (re)wrote UNIX all did it independently
and nobody stole anything from anyone. Brown's remark that people have
tried and failed for 30 years to build UNIX-like systems is patent
nonsense. Six different people did it independently of one another. In
science it is considered important to credit people for their ideas, and
I think Linus has done this far less than he should have. Ken and Dennis
are the real heros here. But Linus' sloppiness about attribution is no
reason to assert that Linus didn't write Linux. He didn't write CTSS and
he didn't write MULTICS and didn't write UNIX and he didn't write MINIX,
but he did write Linux. I think Brown owes a number of us an apology.

Linus and Me

Some of you may find it odd that I am defending Linus here. After all,
he and I had a fairly public "debate" some years back.  My primary
concern here is trying to get the truth out and not blame everything on
some teenage girl from the back hills of West Virginia. Also, Linus and
I are not "enemies" or anything like that. I met him once and he seemed
like a nice friendly, smart guy. My only regret is that he didn't develop
Linux based on the microkernel technology of MINIX. With all the security
problems Windows has now, it is increasingly obvious to everyone that
tiny microkernels, like that of MINIX, are a better base for operating
systems than huge monolithic systems. Linux has been the victim of fewer
attacks than Windows because (1) it actually is more secure, but also (2)
most attackers think hitting Windows offers a bigger bang for the buck
so Windows simply gets attacked more. As I did 20 years ago, I still
fervently believe that the only way to make software secure, reliable,
and fast is to make it small. Fight Features.

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.

Back to my home page
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Francois

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