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How Are Linux and UNIX Related? - UNIX History 101

written by: Jesma•edited by: Michele McDonough•updated: 11/13/2008

In the first of this two-part series on the relationship between Linux and UNIX, learn about UNIX's rich history that defines what it is and who it belongs to.

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    Is Linux Unix?

    If you've asked this question, then you stand shoulder to shoulder with scores of Linux and Unix developers, administrators, and users. What is the verdict? The jury remains undecided. It's a simple question, but ask it to 10 different people and you'll get 10 different answers. The core of the problem lies with how one wants to define each name. Some call it a set of standards, others a community, still others a trademark. In truth, Linux and UNIX are all of these things at the same time.

    Many want to use the old "Duck Test" saying when seeking the answer: "If it looks like a duck, swims like a duck, and quacks like a duck, then the chances are that it is a duck." Besides the obvious flaw in the portability of ducks to complex computer operating systems, the reasoning is largely sound. Linux does resemble UNIX in nearly every way. In fact, the original Linux kernel was modeled after a version of UNIX, and even its creator at times has related it to UNIX.

    Does that mean Linux is UNIX? Not necessarily. If you were to be cloned, would your clone actually be you? Many would argue that what defines something is not necessarily its make-up, but rather its history. In the case of your clone, he/she would not have your same memories or experience, so wouldn't truly be "You".

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    A Brief History of UNIX

    UNIX development truly began in the 1960's under the name Multics, a project that yielded little monetary results and was abandoned by one of the major companies that contributed to its development. However, work on the project was continued by some of the individuals involved and eventually culminated in the birth of Unics (a play on "Multics", later renamed to UNIX) in the 1970's.

    In the 1980s, AT&T implemented commercial licenses on UNIX distributions and streamlined all versions into one: UNIX System V. The University of California, Berkeley, continued development of its own version of UNIX, called BSD. Many of the significant developments in UNIX originally came from BSD - namely the inclusion of TCP/IP code in a major UNIX version.

    Through the 80's and 90's, many companies commercialized and licensed their own versions of UNIX, including Sun Microsystems, Microsoft, and SCO, among others. Around this same time, groups of developers and companies began a hard push for "open" UNIX, creating a further branch in UNIX development. During the early 90's, AT&T sold all of their UNIX rights to Novell. In 1995 Novell sold some of their UNIX rights, including the right to further develop on System V, to SCO.

    All of this buying, selling, licensing, de-licensing, and independent development of the 90's eventually led to law suits, disputes, and drama over who owned what parts of what UNIX. Linux was also thrown into the mix, as one lawsuit filed by SCO claimed that Linux contained copyright UNIX code that belonged to them. When everything was said and done, Novell won the case against SCO, and forced SCO to dismiss its lawsuits against IBM and Sequent, as well as Linux. They went as far as to say that "We do not believe that there is UNIX in Linux."

    Today, Sun Microsystems' Solaris is the largest UNIX operating system. BSD has continued its development and has spawned free versions such as FreeBSD. In 2005 Sun released the majority of its code with OpenSolaris, which has led to even more versions of open source UNIX.

Is Linux UNIX?

Thousands of people have wondered if Linux and UNIX are the same thing, if Linux is a rip-off of UNIX, and where they both came from. Get the facts in this series about the origins and history of both Linux and UNIX, their relationship to each other, and modern application.
  1. How Are Linux and UNIX Related? - UNIX History 101
  2. How are Linux and UNIX Related? - Linux History 101