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Unix Wars and Fragmentation

Availability of source code and portability led to significant fragmentation and rivalry within the Unix ecosystem, primarily occurring from the late 1980s through the early 1990s. This era was characterised by multiple, often incompatible, versions of Unix stemming from different vendors and development branches.

Here's a breakdown of the Unix wars:

  • The Problem of Fragmentation and Incompatibility

    • By the late 1980s, the Unix landscape was plagued by a multitude of implementations. These were typically based on either AT&T's System V, the Berkeley Software Distribution (BSD), or a combination of the two, often with proprietary extensions.
    • This situation stifled the free exchange of source code and led to fragmentation and incompatibility. Although the trademark "UNIX" was ubiquitous, it was applied to a multitude of different, incompatible products.
    • Customers and vendors, such as Informix Corporation, which had over 1,000 product SKUs to serve these variants, began demanding standardisation.

  • Key Factions and Initiatives

    • The principal players in the Unix wars were broadly divided into two main camps:
      • AT&T's System V: AT&T, which initially owned Unix, sought to commercialise the operating system after being relieved of a 1956 antitrust decree in 1983. They introduced UNIX System V into the market.
      • Berkeley Software Distribution (BSD): Developed at the University of California, Berkeley, BSD continued to evolve as an alternative, partly in response to AT&T's more restrictive licensing of newer Unix versions.
    • In an attempt to unify the market, AT&T announced a pact with Sun Microsystems in 1987. This led to the formation of UNIX International (UI), which aimed to merge System V, BSD, SunOS, and Microsoft's Xenix into a single unified Unix, resulting in System V Release 4 (SVR4).
    • However, other vendors viewed this development with concern, believing their markets were threatened. In response, they formed the Open Software Foundation (OSF) to work on their own unified Unix, OSF/1. This division between the UI and OSF camps defined the "Unix wars".

  • Movement Towards Standardisation and Resolution

    • Several standardisation efforts emerged during this period:
      • System V Interface Definition (SVID): AT&T's initial standard, issued in 1985.
      • X/Open Consortium: Established by European computer vendors in 1984, this group aimed to create an open system specification based on Unix. X/Open continued to standardise APIs throughout the wars.
      • POSIX (Portable Operating System Interface): Published by the IEEE in 1988, POSIX was designed as a compromise API that could be implemented on both BSD and System V platforms. It was mandated by the US government for many systems in 1993.
    • The "Unix wars" continued into the 1990s but proved to be less destructive than initially feared.
    • A significant step towards resolution was the Common Open Software Environment (COSE) initiative in 1993, formed by the major Unix players, which marked the end of the most notorious phase of the wars.
    • This was followed by the merger of UI and OSF in 1994, creating a new combined entity that retained the OSF name.
    • In 1993, Novell, which had acquired AT&T's Unix System Laboratories, transferred the "UNIX" trademark and certification rights to the X/Open Consortium.
    • In 1996, X/Open merged with OSF to form The Open Group. The Open Group now owns the UNIX trademark and defines what constitutes a "UNIX" operating system through the Single UNIX Specification (SUS), ensuring compliance and compatibility for certified systems.

  • Impact and Legacy

    • Despite the intense competition, an industry analyst noted in 1989 that "Two Unixes are a lot better than 225".
    • The wars and the subsequent standardisation efforts solidified the Unix philosophy and architecture, paving the way for consistent interfaces.
    • The Unix wars also contributed to the rise of the free software movement. Richard Stallman's GNU Project, initiated in 1983, aimed to create a free Unix-like system, partly in response to the proprietary nature and fragmentation of Unix.
    • The Linux kernel, developed by Linus Torvalds from 1991, was a "reimplementation of Unix from scratch" that avoided the legal issues of original Unix source code, becoming a powerful "Unix-like" alternative.