Unix and Linux History: How E Reach Today

Unix and Linux history, for short

The history of Unix and Linux na one long argument about who get right to own the source code. Unix start for Bell Labs for 1969. Linux start for Helsinki for 1991, and e no share any of that original code. Wetin travel between dem na design and one set of published interfaces: files, processes, pipes, and shell wey join small programs together. Unix spread through universities for the 1970s because one 1956 antitrust settlement stop AT&T (American Telephone and Telegraph) from selling software, so Bell Labs license the source cheaply instead. Unix end up everywhere even though nobody outside AT&T own am, and the licensing fights wey follow decide which free Unix-like system finally end up for your server rack.

1969: spare PDP-7 wey remain, and ideas wey stay

Bell Labs comot from Multics project for 1969. Multics (multiplexed information and computing service) na big time-sharing system wey MIT and General Electric build together, and Labs decide say e too big to finish. Ken Thompson keep the ideas wey e like and drop the rest, then write small time-sharing system for discarded PDP-7 minicomputer. Dennis Ritchie join am. The name Unix na joke against Multics.

For 1970, the system move go PDP-11 wey Labs buy for patent department typists, because text processing tool dey easier to fund than operating system. That machine get 24 KB of core memory, wey system and user programs share. Na this funding accident make the first Unix manual, dated November 1971, be set of formatted documents, and na why you still dey type man 5 crontab. The section numbers for that manual na the same section numbers for your own.

Two changes make the design permanent. Pipes enter Version 3 for 1973, because Doug McIlroy don argue for years say programs suppose fit join end to end, and Thompson add the | operator so output from one program become input for the next program. Then Version 4, later for 1973, dem rewrite am for C. Operating system wey dem write for portable language fit move go hardware wey dem no write am for, and na why Unix survive every machine wey e start on.

Why Unix spread: AT&T no fit sell am

A 1956 consent decree settle antitrust case against AT&T. AT&T keep im telephone monopoly and accept one limit in return: e no go enter businesses wey no be telecommunications. Software na one of those businesses. So when universities ask for Unix, Bell Labs no fit sell am as product. E license the source for small token fee, without support and without warranty.

The effect big, and e no be wetin AT&T plan. Sixth Edition Unix, released for 1975, reach hundreds of computer science departments with full source. John Lions for University of New South Wales print that kernel source with line-by-line commentary and teach from am. One generation learn how operating system dey work by reading real one.

Later, the license change. The Seventh Edition license for 1979 ban people from using the source for classes, so the Lions commentary circulate as photocopies of photocopies. Na so the whole story take be. Unix dey everywhere but e no free at the same time, so every improvement wey anybody make become improvement to another person proprietary code.

Berkeley: Unix parts wey you really dey type

Ken Thompson spend the 1975 to 1976 academic year for University of California, Berkeley, and e leave one very active Unix group behind. Berkeley's Computer Systems Research Group (CSRG) dey release tapes of local improvements, and those tapes become BSD, the Berkeley Software Distribution. Bill Joy write plenty of the early work: 1BSD for 1978, then 2BSD for 1979 with the vi editor and the C shell.

Na the C shell bring !! and !$ come. Bash inherit that syntax, na why bash history expansion still dey surprise people wey type exclamation mark inside double quotes forty-something years later.

DARPA (the US Defense Advanced Research Projects Agency) later pay Berkeley to put the new internet protocols inside Unix. 4.2BSD, wey release for August 1983, ship TCP/IP (transmission control protocol over internet protocol) and the socket application programming interface. Every network service for your server still dey call socket(), bind(), listen() and accept() for that order, because Berkeley pick those names for 1983.

One detail decide wetin happen for the next decade. BSD tape no be complete system. Na set of additions to AT&T's Unix, and you need valid AT&T source license to run am legally. Berkeley replace the AT&T parts with its own code over several years, one file after another. Whether that replacement really complete na the question wey later go court.

1984: breakup, after dat Unix wars

Dem break up Bell System on 1 January 1984, and the consent decree wey bin stop AT&T from software business go along with am. AT&T fit now sell Unix as product, and e do am. Commercial source licenses become expensive, so Unix stop being the cheap thing wey university fit give students.

The vendors don already fork am. Every workstation company dey ship im own Unix for im own hardware, so by late 1980s, program wey dem write for one system need porting before e fit work for another. The industry split into two standards camps for 1988: Open Software Foundation for one side and Unix International for the other. Dem spend years shipping systems wey no compatible while dem dey argue about which Unix be the real one.

POSIX (portable operating system interface) come out from that mess. IEEE 1003.1 publish for 1988, and e write down wetin Unix-like system suppose do: the system calls, shell behaviour, standard utilities, and C library interfaces. This matter pass as e sound, because standard na specification and no license dey cover am. Three years later, one student write kernel based on those documents.

Minix, and di gap wey e leave

Andrew Tanenbaum release Minix for 1987 as teaching system for im operating systems textbook. Minix na small Unix-like system, di book come with di source, and e run for di cheap PCs wey students really get. E legal to read am for classroom, but Seventh Edition Unix no longer get that kind freedom.

Minix remain small on purpose, because dem need explain am inside book, and Tanenbaum reject patches wey for turn am into production system. Di license no free too: you buy di book, and na you no get decision to redistribute your modified Minix. So by 1991, student fit read working Unix-like kernel, but e no fit build anything wey go last on top am.

GNU get everything except kernel

Richard Stallman announce GNU project for September 1983, with aim to build complete free Unix-like system. By 1991, GNU don produce most of the parts wey dey surround kernel: GCC compiler, GNU C library, binary utilities, and bash, the shell wey Brian Fox write for 1989 and the shell wey your server still start you inside. GNU kernel, Hurd, na the part wey keep dey delay.

GNU General Public License version 2 publish for June 1991. The rule short. You fit use the code and change am, and if you distribute the result, you must distribute the source under the same terms. That rule go become the main link for this story two sections from now.

August 1991: the post go comp.os.minix

For 25 August 1991, one student for Helsinki post to Usenet group comp.os.minix:

Hello everybody out there using minix -

I'm doing a (free) operating system (just a hobby, won't be big and
professional like gnu) for 386(486) AT clones.

Version 0.01 come out for September 1991. E no share code with Unix or Minix. Na new kernel for the 386, wey dem develop for Minix machine, write against the POSIX interfaces, and pair with the GNU tools wey don already dey. For January 1992, Tanenbaum tell Torvalds say monolithic kernel na obsolete design. E get valid point about design, but Torvalds dey answer another question: wetin fit run well for the one cheap computer wey student get.

For February 1992, dem relicense version 0.12 under GPL. Torvalds don later call am im best decision. The original Linux license no allow anybody make or collect money from am. That one for block the CD vendors and support companies wey come after. GPL allow people do business, but e force every change wey dem distribute to go back into the same shared tree.

The lawsuit: April 1992 to February 1994

Berkeley release Networking Release 2 (Net/2) for June 1991: na almost complete BSD system, with the files wey come from AT&T don comot. Six kernel files no dey. Bill and Lynne Jolitz write replacement dem and release 386BSD 0.0 for March 1992, then 386BSD 0.1 for 14 July 1992. Free, complete, mature BSD for the 386 don dey available by then, for the same period wey Linux still be hobby kernel. Berkeley Software Design, Inc. (BSDi) sell supported commercial build, BSD/386, and advertise am with telephone number 1-800-ITS-UNIX.

For April 1992, Unix System Laboratories (USL), the AT&T subsidiary wey own Unix at that time, sue BSDi for federal court for New Jersey over trade secrets and Unix trademark. Dem later amend the lawsuit to add the Regents of the University of California. The University file counter-lawsuit for California for 1993, arguing say AT&T ship Berkeley code inside System V without the credit wey its own license require.

The main legal issue begin break apart for 1993. Judge Dickinson Debevoise reject USL request for preliminary injunction. The judge believe say USL copyright claim over the older 32V code probably no valid, because AT&T distribute the code for years without copyright notices. Novell buy USL from AT&T for the middle of 1993, and Novell management want make the case end. The parties settle the case for February 1994. From roughly 18,000 files for the Berkeley distribution, dem remove three, and about seventy receive USL copyright notices.

Berkeley ship 4.4BSD-Lite for June 1994, and the release legally clean. FreeBSD and NetBSD, wey both start for 1993 on the disputed Net/2 code, then need rebuild their systems on the new base. This work take most of the remaining 1994. Linux 1.0 release for March 1994, while this rebuild still dey happen.

Linux take the server instead of BSD because of wetin?

The lawsuit na the popular answer, and e dey part of the answer. Between April 1992 and February 1994, anybody wey choose free Unix for product had to weigh an active claim from AT&T lawyers against kernel from one Finnish student wey nobody fit sue over. Na that exact period web show up and the first Linux distributions appear: Slackware for July 1993, Debian for August 1993, then Red Hat and SUSE.

Four other things matter as much as the court case.

• Hardware. Linux target the commodity 386 PC from the first line of code, and na that hardware later become cheap. BSD main focus na VAX and workstation, while two people for outside work handle the 386 port.
• The license. GPL require company wey dey ship modified kernel to publish its changes, so vendor work flow back into one tree. BSD license allow company keep its changes private, and companies really keep dem private.
• The development model. Torvalds merge patches from strangers quickly and release constantly. 386BSD release slowly enough that its own users fork am twice for 1993, into NetBSD and FreeBSD, and again into OpenBSD for 1995.
• Momentum. Developers dey go where other developers already dey, and drivers dey get written for the system wey get the most users.

Make we talk true about the technical question. BSD for 1994 na the more finished system, with coherent base, documented history, and networking code wey Linux spend years trying to catch up with. Nobody choose Linux for 1994 because e better. People choose am because e dey available, nobody put restriction on am, e dey run for hardware wey dem already get, and e dey improve every week.

Wetin BSD hold on to, and where e dey run now

BSD no stop. Wetin e lose na the default position. The clearest proof dey for your own machine: the OpenBSD project write OpenSSH for 1999, and na the SSH server for almost every Linux system wey dey release today. Na why the SSH key habits wey worth learning dey the same for both families.

Netflix dey serve video from FreeBSD appliances. Junos, wey be the operating system for Juniper routers, get FreeBSD underneath. PlayStation system software come from FreeBSD. Apple's macOS and iOS carry BSD code for the kernel and across the userland. The permissive license wey make BSD lose the shared server tree put BSD code inside plenty hardware wey no ever mention am.

If you dey choose today, the question practical pass historical one. Comparing Linux and FreeBSD as a server come down to ZFS, jails, the ports tree, and how much third party software dey assume say Linux dey underneath. FreeBSD 15 as a server na current, maintained system, no be museum exhibit. And Linux against Windows Server na separate question, with answer wey depend on your application stack.

The 1969 design wey you dey use for VPS today

Each one of dem old pass plenty people wey dey use am today.

• The pipe. who | wc -l dey count users wey log in because Version 3 Unix for 1973 allow output from one program become input for another program.
• The manual sections. man 1 ls and man 5 crontab dey use numbering scheme from the November 1971 manual.
• The filesystem split. /usr dey exist because root disk for that PDP-11 full up for 1971, so developers move files go the second disk pack. Distributions don later undo the split: run ls -ld /bin for Ubuntu 24.04 or Debian 13, and you go get symbolic link to usr/bin.
• The socket calls. Berkeley write dem for 4.2BSD for 1983, and every network daemon still dey use dem.
• POSIX. A #!/bin/sh script wey dem write according to the standard go run unchanged for Linux, FreeBSD, macOS, and Solaris, because na the standard all of dem implement.

When you rent virtual private server and log in, you dey type for interface wey dem design for machine wey get 24 KB memory and patent department to support. E survive because dem publish the interface, people argue about am, standardise am, then people wey no ever get permission to see the original code implement am again from scratch.

FAQ

Linux get any original Unix code inside?

No. Linus Torvalds write the kernel from scratch for 1991, and e target POSIX interfaces instead of any AT&T source. The Unix inheritance na design and published interface: files, processes, pipes, and system call names. Dem write the GNU tools wey surround the kernel from scratch too, starting for 1983. Na this independence make the AT&T litigation over BSD code no ever touch Linux at all.

When AT&T lawsuit against BSD happen, and e kill BSD?

USL, the AT&T subsidiary wey own Unix, sue BSDi for April 1992 and later add University of California as defendant. For 1993, the judge refuse preliminary injunction because e hold say the copyright claim over the older 32V code likely no valid. Novell buy USL for mid-1993 and settle the case for February 1994. Dem remove three files out of about 18,000, and give roughly seventy new copyright notices. E no kill BSD. E freeze BSD adoption during the two years wey the world dey choose a free Unix.

Why Linux take over servers instead of BSD?

Legal certainty na one reason: throughout 1992 and 1993, Linux carry no lawsuit, while BSD carry one. The other reasons na 386 as target from day one, GPL wey pull vendor changes back into one tree, and merge process wey fast enough to keep contributors interested while 386BSD fork three ways. Technical merit no be the deciding factor, because BSD na the more finished system for 1994.

FreeBSD still worth running today?

Yes, and concrete reasons dey: ZFS integrate with the base system, jails as mature isolation model, base system wey dem develop as one coherent unit, and documentation wey stay accurate. The cost na compatibility work, because most third party server software, container tooling, and vendor support assume Linux. Pick FreeBSD when the storage and networking work wey e provide justify that cost, instead of choosing am because of loyalty to the older lineage.