Slackware/Linux/Unix (pre-)history (Part 3: Unix-wars, and peace)
The big split
The first versions of Bell Labs’ Unix. also known as ‘Research Unix’, included the full source code, allowing universities to improve and extend the operating system. As I wrote in the previous post in this series, UCB did a lot to add to Unix and created its own distribution – BSD.
The first version – 1BSD – was more like a set of add-ons and patches compiled by Bill Joy. Bit by bit, BSD became larger and larger, with every release coming closer to be a complete operating system.
In 1981 AT&T started selling commercial licenses of Unix, largely based on version 7 of Unix from Bell Labs, and called it System III. After including some of the BSD additions, like vi and curses, it released System V – Release 1 in 1983.
These two branches, BSD and System V, were incompatible.
Bill Joy founded SUN in 1983 with three graduate students from Stanford University who all had worked on the Stanford University Network, one of the four original ARPAnet nodes. They developed the SUN workstations running SunOS, based on BSD.
While the BSD-based versions dominated the workstation market, several new commercial versions were developed for the server market based on System V, like IBM’s AIX and HP’s HP-UX.
Attempts to standardize
Several attempts were made to create standards:
- In 1983 a Unix users group called UniForum published the Uniforum Draft Standard, UDS83. It was based on AT&T’s System III and 4.1BSD. But shortly after 4.2BSD was released with many new features (including TCP/IP) creating several incompatibilities.
- In 1985 AT&T released the System V Interface Definition (SVID), formally describing the SysVr2 API and including UDS84. SVID3, following SysVr4, became the basis for IEEE’s POSIX standard, tipping the balance more in AT&T’s direction than in BSD’s.
- A consortium of Unix vendors formed X/Open in 1984 and developed the X/Open Portability Guides (XPG), describing a subset of features compatible with all Unixes.
In 1993 the war finally ended with seventy-five vendors of hardware and software declaring support for X/Open. With this deal, the X/Open consortium acquired the rights to the Unix trademark and created the Single Unix Specification version 1.
In 1999 X/Open absorbed all activities related to the POSIX standard.