Unix wars

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The Unix wars were the struggles between vendors of the Unix computer operating system in the late 1980s and early 1990s to set the standard for Unix thenceforth.


Although AT&T Corporation created Unix, by the 1980s the University of California, Berkeley Computer Systems Research Group was the leading noncommercial Unix developer.[1] In the mid-1980s, the two common versions of Unix were Berkeley's BSD and AT&T's System V. Both were derived from the earlier Version 7 Unix, but had diverged considerably. Further, each vendor's version of Unix was different to some degree.

For example, at a mid-80s Usenix conference, many AT&T staff had buttons which read "System V: Consider it Standard" and a number of major vendors were promoting products based on System V. On the other hand, System V did not yet have TCP/IP networking built in and BSD 4.2 did; vendors of engineering workstations were nearly all using BSD and posters that said "4.2 > V" were available.

A group of vendors formed the X/Open standards group in 1984, with the aim of forming compatible open systems. They chose to base their system on Unix.

X/Open caught AT&T's attention. To increase the uniformity of Unix, AT&T and leading BSD Unix vendor Sun Microsystems started work in 1987 on a unified system. (The feasibility of this had been demonstrated a few years earlier by the US Army Ballistic Research Laboratory's System V environment for BSD Unix.) This was eventually released as System V Release 4 (SVR4).

While this decision was applauded by customers and the trade press, certain other Unix licensees feared Sun would be unduly advantaged. They formed the Open Software Foundation (OSF) in 1988. The same year, AT&T and another group of licensees responded by forming UNIX International (UI). Technical issues soon took a back seat to vicious and public commercial competition between the two "open" versions of Unix, with X/Open holding the middle ground. A 1990 study of various Unix versions' reliability found that on each version, between a quarter and a third of operating system utilities could be made to crash by fuzzing; the researchers attributed this, in part, to the "race for features, power, and performance" resulting from BSD–System V rivalry, which left developers little time to worry about reliability.[2]


In March 1993 the major participants in UI and OSF formed the Common Open Software Environment (COSE) alliance, effectively marking the end of the most significant era of the Unix wars. In June, AT&T sold its UNIX assets to Novell, and in October Novell transferred the Unix brand to X/Open.

In 1996, X/Open and the new OSF merged to form the Open Group. COSE work such as the Single UNIX Specification, the current standard for branded Unix, is now the responsibility of the Open Group.

Since then, occasional bursts of Unix factionalism have broken out, such as the HP/SCO "3DA" alliance in 1995, and Project Monterey in 1998, a teaming of IBM, SCO, Sequent and Intel which was followed by litigation (SCO v. IBM) between IBM and the new SCO, formerly Caldera.

BSD and the rise of Linux[edit]

The Berkeley Software Distribution emerged as an independent Unix-like operating system, and began purging of copyrighted AT&T code from 1989 to 1994. During this time various open-source BSD x86 derivatives took shape, starting with 386BSD, which was soon succeeded by FreeBSD and NetBSD. OpenBSD emerged in 1995 as a fork of NetBSD, DragonFly BSD as a fork from FreeBSD in 2003. Mac OS X v10.5 is the first operating system with open source BSD code to be certified as fully Unix compliant.[3] BSD systems can claim direct ancestry to Version 7 Unix. Or, according to Open Source advocate Eric Raymond, BSD systems can be considered "genetic Unix", if not "trademark Unix."[4]

During BSD's period of legal turmoil (1992-1994), the nearly-complete GNU operating system was made operational by the inclusion of the Linux kernel and lumped together under the label "Linux." The system was written from scratch to avoid copyright issues. Linux systems broadly aim for compatibility with POSIX.

See also[edit]


  1. ^ Fiedler, Ryan (October 1983). "The Unix Tutorial / Part 3: Unix in the Microcomputer Marketplace". BYTE. p. 132. Retrieved 30 January 2015. 
  2. ^ Miller, Barton P.; Fredriksen, Louis; So, Bryan (1990). "An empirical study of the reliability of UNIX utilities" (PDF). Communications of the ACM 33 (12): 32–44. doi:10.1145/96267.96279. 
  3. ^ Mac OS X Leopard Achieves UNIX 03 Product Standard Certification
  4. ^ http://www.internetnews.com/dev-news/print.php/2208691