What is BSD (Berkeley Software Distribution)?

BSD (Berkeley Software Distribution) is used by the University of California at Berkeley to describe an operating system derived from the Unix system, resulting from contributions to this system.

What is BSD (Berkeley Software Distribution)?

What is BSD Operating System?

In the early years of the Unix system, its creators authorized AT&T Company Bell Labs, University of California, Berkeley, and other universities to use the source code and adapt it to their needs.

In the 1970s and 1980s, Berkeley used the system for operating systems research. When AT&T withdrew its permission to use from the university for commercial reasons, the university encouraged the creation of a version inspired by the Unix system using their contributions. It subsequently allowed for its distribution for academic purposes and reduced the minimum restrictions on its copying, distribution, or replacement after a while.


   Beginning with PDP-11

Bell Labs’ first Unix distributions in the 1970s included the source code of the operating system and allowed university developers to replace and extend Unix. Berkeley’s first Unix system was the PDP-11, which was founded in 1974 and has been used by the computer science department since its research.

Other universities became interested in Berkeley software, and in 1977, Berkeley graduate Bill Joy recorded and sent the tapes of the first Berkeley Software Distribution.

BSD 1 is a supplement to the sixth version of Unix, more than a full operating system. It consisted essentially of a Pascal compiler and a text editor called “ex” by Joy.

The BSD 2 was released in 1978, it included updated versions of 1BSD and two new programs by Joy on Unix systems to date: Vi text editor and C shell. The following versions included adaptations that made their distributions based on the VAX architecture compatible with the PDP-11 architecture.

Since 1983 BSD-2.9 includes BDS 4.1c code and is the first distribution considered as a full operating system. The latest release, version 2.11, was released in 1992 and continued to be updated until 2003 with the help of volunteers.

   VAX Versions

A VAX computer was installed in Berkeley in 1978, but the adaptation of Unix to the VAX architecture UNIX/32V did not take advantage of this architecture’s virtual memory capacity.

The 32V core was practically rewritten by Berkeley students to take advantage of virtual memory, and finally, at the end of 1979, a new core, 3BSD with 2BSD adaptations to the VAX architecture and 32V utilities was launched.

BSD-3 was also called BSD/vmunix kernel images up to Virtual VAX/UNIX or VMUNIX and BSD-4.4.

Success with BSD-3 was a determining factor for Berkeley’s CSRG (Computer System Research Group) for DARPA, who wanted to develop a standard Unix platform for her research in the VLSI project.

   BSD 4

Launched in November 1980, it offered many improvements, especially the control work of the previous version of csh, mail delivery, reliable signals, and the Curses programming library.

   BSD 4.1

This release, released in June 1981, responded to BSD’s criticism compared to the dominant operating system for the VAX architecture VMS. Developed by Bill Joy until it has the same features as VMS.

The distribution was originally called BSD-5, but it was modified to prevent possible confusion with the launch of the AT&T Unix System V.

   BSD 4.2

This version took two years to implement and included major improvements.

Three intermediate versions appeared before the official version. 4.1a contains a modified version of the BBN’s TCP/IP pre-application. 4.1b included the new Berkeley Fast File System implemented by Marshall Kira McKusick, and 4.1c was an internal release used in the last months of 4.2 development.

The official distribution was released in August 1983. Bill Joy became the first distribution after leaving and installing Sun Microsystems. Mike Karels and Marshall Kira MacKusick have since taken over the project.

   BSD 4.3

BSD4.3 was released in June 1986. Their main change was the improvement of many new additions that were not improved, such as BSD4.3 code. Before launching, TCP/IP implementation has deviated significantly from the official application run by BBN.

Therefore, after many tests by DARPA, he concluded that the version in 4.2 is superior to the new one and therefore should be kept in the new distribution. After version 4.3, it was determined that future versions should already be created based on a different architecture than the old VAX.

At that time, Power 6/32, developed by Computer Consoles Inc, looked like a platform with more future, although it was soon abandoned by its developers. However, 4.3-Tahoe, adaptation to this platform, proved the value of the distinction between the machine-dependent code and the independent code that allows future portability.

Until now, all versions of BSD included AT&T proprietary code that required a license to use. These have become very expensive, so many external organizations have expressed their interest in a separate distribution of private network code developed by AT&T so that these licenses are not paid. This was accomplished with Network Band 1 (Net/1) created without the proprietary code of AT&T, released in 1989 and freely distributed under the permitted license terms.

   BSD 4.3-Reno

4.3-Reno was released in 1990 and was an internal use version used in its construction. This distribution was moving towards compatibility with POSIX, and according to some, it was far from philosophy as it was based on the POSIX V system.

   Net/2 and Legal Issues

After Net/1, Keith Bostic suggested publishing more non-AT & T-BSD episodes with the same Net/1 license.

To this end, he launched a project aimed at implementing most of the standard Unix utilities without AT&T code. Within 18 months, all of AT&T’s registered public services were replaced and only a few registered files remained in the core. These files were finally eliminated and Net/2 was an almost complete operating system and could be freely distributed.

Net/2 was the basis for two separate adaptations for Intel’s 80386 architecture, William Jolliz’s 386BSD and the registered BSD/386 of Berkeley Software Design (BSDi). 386BSD is short-lived, but it is the starting point for FreeBSD and NetBSD.

BSDi soon experienced a legal issue with AT&T, owners of System V rights, and the Unix brand. The lawsuit was filed in 1992, provided that Net/2 was not distributed until the validity of the claims was determined.

The case slowed its development for nearly two years when BSD’s legal grandparents were concerned.

Linux and 386BSD began to evolve simultaneously, and even Linus Torvalds said that if it were a free Unix-based operating system for the 386 architecture, it probably would not create Linux. Although it is controversial what effect it can have in the software field, it is certain that it will be important.

   BSD 4.4

The case was concluded in favor of Berkeley in January 1994. Only three of the 18,000 files in the distribution have been removed and 70 have been changed to show AT&T’s property rights.

In June 1994, this version was released in two versions: one called 4.4-Lite and can be freely distributed without special code, and 4.4-Encumbered only for AT&T vendors.

The final distribution created by Berkeley was BSD 4.4-Lite Version 2, released in 1995 after the CSRG was resolved. Since then, many BSD 4.4-based distributions such as FreeBSD, OpenBSD, and NetBSD have appeared.

In addition, the permitted license allowed to include the code of other operating systems, both free and registered.

For example, Microsoft used code derived from BSD in the Windows TCP/IP application and uses recompiled versions of the command line for network tools.

In addition, Darwin, where Apple’s operating system, Mac OS X, was installed, was partly derived from FreeBSD 5. Other commercial Unix-based systems like Solaris also use BSD code.


Some sub-operating systems of the system developed by Berkeley are SunOS, FreeBSD, NetBSD, OpenBSD, and Mac OS X. It also made major contributions in the field of operating systems in general:

  • Optional paged virtual memory management
  • Business control
  • Fast File System
  • TCP/IP protocol (almost all TCP applications are derived from 4.4BSD-Lite)

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