Unix wars

Origins

Both AT&T Corporation and University of California, Berkeley are important in the early history of Unix. Although AT&T's Bell Labs created Unix, by the 1980s, Berkeley's Computer Systems Research Group was the leading non-commercial Unix developer. In the mid-1980s, the three common versions of Unix were AT&T's System III, the basis of Microsoft's Xenix and the IBM-endorsed PC/IX, among others; AT&T's System V, which it sought to establish as the new Unix standard; and the Berkeley Software Distribution (BSD). All were derived from AT&T's Research Unix but had diverged considerably. Further, each vendor's version of Unix was different to some degree.

For example, at a mid-1980s Usenix conference, many AT&T staff had buttons that 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, while BSD 4.2 did; vendors of engineering workstations were nearly all using BSD, and posters reading "4.2 > V" were available.

Several vendors formed the X/Open standards group in 1984 to promote compatible open systems, and 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 released in 1988 as System V Release 4 (SVR4) which still lives to this day through its derivative OpenIndiana.

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 in 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.