Few pieces of software have shaped modern computing as deeply as the Berkeley Software Distribution (BSD), the flavor of Unix born at the University of California, Berkeley in the late 1970s. From that academic project came vi, the C shell, a virtual memory implementation and, above all, the TCP/IP networking stack that still underpins the internet today. This is the story of that original BSD.
Origins: from AT&T Unix to Berkeley
In the mid-1970s, Berkeley received a copy of AT&T’s Unix and began improving it. The early star of the project was Bill Joy, a graduate student who would later co-found Sun Microsystems. In 1977 Joy assembled the first distribution, 1BSD, which was not a complete system but a set of add-ons for AT&T Unix, including a Pascal compiler and the ex editor.
The second release, 2BSD (May 1979), introduced two programs still found on Unix systems today: the vi text editor and the C shell. The 2BSD line, aimed at PDP-11 machines, enjoyed a remarkably long life, with updates spanning decades.
3BSD and the birth of the CSRG
The real leap came with 3BSD, released at the end of 1979. Its kernel, derived from the 32V version of Unix for the VAX, was rewritten to include a virtual memory implementation largely developed by graduate student Özalp Babaoğlu. 3BSD was a complete operating system, not just a patch.
The success of 3BSD convinced DARPA, the Pentagon’s research agency, to fund Berkeley to build a standard Unix platform for its projects. That led, in 1980, to the creation of the Computer Systems Research Group (CSRG), which would steer BSD development for fifteen years.
4.2BSD: the TCP/IP revolution
After 4BSD (October 1980) and the finely tuned 4.1BSD came the most influential release of all, in August 1983: 4.2BSD. Its landmark contribution was integrating the TCP/IP networking stack and the Berkeley sockets interface, the network programming model that became a universal standard. When the internet took off in the 1980s and 1990s, it did so largely on top of code inherited from Berkeley.
4.2BSD was also the first version released after Bill Joy left for Sun Microsystems in 1982. From then on, technical leadership passed to Mike Karels and Marshall Kirk McKusick.
4.3BSD and the releases that gambled their names
4.3BSD arrived in June 1986, focused on polishing and tuning the performance of features that 4.2BSD had introduced in a hurry. It was followed by variants with curious names: 4.3BSD-Tahoe (1988), which separated machine-dependent from machine-independent code and improved portability, and 4.3BSD-Reno (1990), an interim release seen as a gamble — hence the nod to Reno, Nevada’s gambling town.
The AT&T lawsuit and the end of the CSRG era
The biggest headache was legal. To distribute BSD freely, Berkeley set out to remove all AT&T code and replace it with its own, producing Net/2 (1991) under the BSD license. In April 1992, AT&T’s Unix System Laboratories subsidiary sued the company BSDi and later the University of California itself.
The case was settled in January 1994, largely in Berkeley’s favor: of the 18,000 files in the distribution, only three had to be removed and around seventy were modified to carry copyright notices. The group’s final release was 4.4BSD-Lite Release 2 in 1995, after which the CSRG was dissolved and Berkeley ceased BSD development.
The legacy: FreeBSD, OpenBSD and NetBSD
That code never died — it became the direct ancestor of today’s major free BSDs. From 4.4BSD-Lite descend FreeBSD, NetBSD and OpenBSD, three systems still very much alive in servers, networking gear and security projects. The Berkeley spirit also runs through systems like Solaris and AIX, and its open philosophy inspired later communities, including that of the Linux kernel.
A fun fact: the BSD daemon
BSD’s friendly mascot, the little red demon with a trident, has a distinguished origin: its first drawing on the covers of the manuals distributed by USENIX with 4.2BSD was the work of John Lasseter, who years later would direct Toy Story at Pixar. A detail that nicely captures the spirit of a project where serious engineering met a good sense of humor.