Berkeley Software Distribution

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Berkeley Software Distribution
Word mark
developer University of California at Berkeley
License (s) BSD license
Current  version 4.4BSD-Lite2 ( 1995 )
Kernel Monolithic
ancestry Up to and including version 4.3BSD:
from version 4.4BSD:
BSD (re-implemented)
Architecture (s) PDP-11 , VAX , Intel 80386
Others Development discontinued.
Continuation through BSD derivatives

The Berkeley Software Distribution ( BSD ) is a variant of the Unix operating system that was created at the University of California in Berkeley from 1977. BSD is based on AT & Ts Unix Sixth Edition (V6) and Seventh Edition (V7) from 1975 (V6) and 1979 (V7).

At that time, AT&T still held the telecommunications monopoly in the USA and was not allowed to do business in the computer sector, so the UNIX company distributed the data carriers to universities at cost price. Associated with this was the permission to view and modify the source text . It was later preserved for teaching purposes. After AT&T demanded UNIX license payments in the 1990s, the source code was rewritten so that there is no longer a single line of original UNIX source code from AT&T in current BSDs.

The original BSD created by the university is practically no longer in use. Rather, the term BSD today describes a whole class of operating systems that are derived from the Berkeley Software Distribution. Along with System V, BSD is one of the great main lines of Unix development.

Today macOS from Apple , the most commercially successful BSD and Unix for personal computers  - a development of NeXTs OPEN STEP . It is based on the basic Darwin operating system , which was developed on the basis of FreeBSD , OpenBSD and NetBSD . Darwin includes the hybrid kernel XNU , the development of which is based on the OSF Mach kernel and the FreeBSD kernel. A variety of resources for the command line complement Darwin in macOS, a large part of which comes from FreeBSD, OpenBSD and NetBSD. The founders of Apple and NeXT were students at Berkeley.

The BSD license

The source code of the distribution was released by Berkeley under the BSD license, which, in its modified form today, is a free license that is also used for other program packages. In contrast to the GNU General Public License , the BSD license allows you to use the source code to develop your own, proprietary programs while observing a few rules.

New from Berkeley

BSD had a huge impact on Unix development. Changes have been made to the kernel and the system has been significantly expanded in other ways. Many of these innovations were later incorporated into the competing System V line either directly or in a similar form.

The most important innovations were:

Development history

BSD evolved from Bell-Labs' Unix.

The following is the history of Berkeley Software Distribution from the acquisition of a copy of Unix from Bell Laboratories by UCB up to version 4.4-Lite2.

The beginnings

In 1974, the University of Berkeley received the 4th edition of the still new Unix operating system from AT&T. This had just been rewritten in C , a C development system was part of the system. The expansion of the system, which was running on a PDP-11 machine from Digital Equipment Corporation (DEC), began immediately . Work accelerated when in 1976 Ken Thompson , a key Unix developer, took up a visiting professorship at Berkeley. In the meantime, editions 5 and 6 had also appeared.

The then student Bill Joy summarized the extensions and changes for the first time in 1977 and made them available to interested parties on a magnetic tape - the first Berkeley software distribution. By 1978, so many new parts had been added that the second Berkeley Software Distribution (2BSD) was put together. This already contained the first version of the editor vi .

VAX computers and DARPA influence

In the meantime, DEC had released a new line of processors called VAX, the first representative of which was the VAX-11/780. VAX was actually called Virtual Address Extension and was initially intended as an extension for the PDP-11 line. However, the VAX became its own processor line, and DEC planned to stop selling PDP machines in favor of the VAX line. AT&T had already completed a port from Unix V7 to the VAX processor (version 32 / V), but this did not support virtual memory management. Berkeley ported 2BSD to the VAX-11/780 and implemented virtual memory management. For VAX machines, 3BSD appeared in 1979 and then 4BSD in 1980. The development of BSD versions for PDP-11s was continued independently with 2BSD, since the address space of the PDPs of only 64 Kbytes was too small for the new versions.

In 1980, a contract was signed with the research department of the American Department of Defense DARPA . 3BSD and 4BSD should become the basis for DARPA developments, especially in the area of ​​networking. This led to the integration of the Internet network protocols (TCP / IP) in the BSD variants.

At the same time, AT&T decided to develop its Edition V7 into System III and then into System V and to market it commercially. The new Berkeley version was therefore not called 5BSD, but 4.1BSD to avoid confusion. With 4.1BSD and the internal versions 4.1a, 4.1b and 4.1c, the performance of the system was improved, the first TCP / IP protocols were added and network tools (rsh, rcp) were developed. This , along with many of Berkeley's utilities, prompted Sun , DEC, and other hardware manufacturers to base their versions of UNIX on BSD instead of the official System V from AT&T. This is how BSD established itself in the academic and military sectors. AT&T later incorporated these developments into their System V product. Because the Berkeley distribution still contained early AT&T source code, AT&T required the purchase of an expensive license from anyone using Berkeley code.

The commercial era


Computer manufacturers took over Berkeley Software Distribution and adapted it to their machines. In 1982 Bill Joy moved to the newly founded company Sun Microsystems , which in the same year released the first version of its BSD-based operating system SunOS . In the course of its development history, SunOS was expanded to include many functions of the already licensed System V, but remained true to its BSD roots for a long time.

In 1983 DEC released Ultrix-11 for PDP-11 and then Ultrix-32 for VAX computers. Ultrix was also based on BSD. It was later ported to MIPS processors that DEC used in its workstation line.

Other Unix manufacturers also used parts of the BSD. From 1988 onwards , NeXT used a BSD system for its NeXTStep operating system, albeit with a Mach microkernel. System V gradually adopted code from BSD and formed the basis of these Unix systems.


DEC brought out their Alpha microprocessor around 1990 , which should replace the VAX and MIPS products. At the same time, the further development of Ultrix was stopped because the new OSF / 1 - a Unix clone - was offered on Alpha .

In 1988 Sun formed an alliance with AT&T with Unix International and also ported their SunOS to System V with BSD extensions. In 1992 SunOS5 (also Solaris  2) appeared, which was no longer a direct descendant of BSD.

The last major Unix manufacturer had switched to System V, but all Unix systems still used large parts of the BSD, including the commands introduced by BSD and the TCP / IP network implementation.

Developments at Berkeley

Berkeley continued its tradition and developed the distribution further. In 1983 4.2BSD was released and in 1986 4.3BSD. It became clear that the VAX processors had to be replaced by other systems, with 4.3BSD-Tahoe (1988) the kernel was separated into machine-dependent and portable parts. In 1990, 4.3BSD-Reno was released, a version that supported the Mach microkernel, among other things .

4.3BSD was even (back) ported to the PDP-11 machines and released as 2.11BSD in 1992. The 250 KByte kernel was mapped to the only 64 KByte large address space of the PDP using overlay techniques.

BSD and AT & Ts Unix source code

By the late 1980s, Berkeley had built so many extensions that almost all of AT & T's Unix source code was replaced by its own versions. Manufacturers of BSD-based Unix versions still had to purchase an expensive System V license from AT&T because of the remaining parts. Since, among other things, the entire network implementation came from Berkeley, other manufacturers were also interested in the Berkeley developments, but without having to acquire an AT&T license. In 1989 the university therefore issued the Networking Release / 1 , which included all files identified by Berkeley without code from AT&T. However, this version was no longer a complete operating system.

In 1991 the Networking Release / 2 appeared . Bill Jolitz added only six files to this release in 1992 and released a patch so that a complete, advanced operating system for Intel 80386 processors called 386BSD was created.

Also in 1992, a company founded by the University of Berkeley called Berkeley Software Design Inc. (BSDi) began marketing the Networking Release / 2, which was also expanded to become an operating system. They marketed their system under the name "Unix" including source code for the lower price of 995 dollars. The Unix System Laboratories (USL), a branch of AT&T, sued BSDi and the university thereupon for discontinuing sales due to trademark infringement and partial use of their source code. However, an injunction was rejected.

In the course of this lawsuit, it emerged that AT&T had taken over source code from Berkeley (which was legal because of the BSD license), but had removed Berkeley's authorship from the source code and documentation (which is prohibited in the BSD license). The lawsuit ended in 1994 with AT&T having to re-register Berkeley authorship in some of its files. Berkeley only had to remove three of the 18,000+ files from Networking Release / 2 and make a few small changes. The release was thus free of Unix source code.

In the same year Berkeley then released version 4.4BSDLite as the successor to the Networking Release / 2. In 1995 version 4.4BSDLite2 was the last version of the Berkeley software distribution. 4.4BSDLite and Lite2 together with 386BSD became the basis of NetBSD, FreeBSD and shortly afterwards OpenBSD.

BSDi continued to develop and sell its system under the name BSD / OS. In 2001 BSDi was bought by the Californian company Wind River Systems .


version publication Remarks
BSD 1977
2BSD 1978
  • Further development (PDP-11)
  • Extract (programs): vi
3BSD 1979
4BSD 1980
  • Further development (VAX)
  • Extract (programs): mail , job control
2.8BSD 1981
  • Further development (PDP-11)
4.1BSD 1981
  • Further development (VAX)
  • Various performance improvements
4.1BSDx 1982
  • Internal versions: BSD4.1a, BSD4.1b, BSD4.1c
  • Network development
  • Various performance improvements
2.9BSD 1983
  • Further development (PDP-11)
4.2BSD 1983
4.3BSD 1986
  • Robust network implementation
  • Various performance improvements
4.3BSD-Tahoe 1988
  • Separation of the machine-dependent and portable kernel parts
2.10.1BSD 1989
  • Last version and further development of the original PDP-11 line
4.3BSD-Net / 1 1989
  • Networking Release / 1
4.3BSD-Reno 1990
4.3BSD-Net / 2 1991
  • Networking Release / 2 (also 4.3BSD-Lite )
2.11BSD 1992
  • Backport from 4.3BSD to PDP-11
BSD / 386 1992
  • Commercial version from Berkeley Software Design, Inc. with support for Intel i386 processors
386BSD 1992
  • Porting of 4.3BSD-Lite to Intel i386 processors by Bill Jolitz
4.4BSD-Lite 1994
  • First version completely free of AT&T source code (also 4.4BSD-Encumbered )
BSD / OS 1994
  • Further development (386BSD)
  • Additional support for Sun SPARC and PowerPC processors
4.4BSD-Lite2 1995
  • Last version of the Berkeley Software Distribution

The NetBSD, FreeBSD and OpenBSD projects

Unix family tree

The free 386BSD (1992) by Bill Jolitz attracted developers, especially since PCs with 80386 processors became very inexpensive. Jolitz was permanently employed and did not always have enough time to correct errors and incorporate suggestions for improvement. This prompted some developers in 1993 to launch two follow-up projects, NetBSD and FreeBSD, almost simultaneously.

After the dispute with AT&T was settled in 1994, both projects released new versions based on 4.4BSD-Lite that no longer contained AT&T source code: NetBSD 1.0 (1994) and FreeBSD 2.0 (early 1995).

In 1995 one of the founders of the NetBSD project, Theo de Raadt , fell out with the other developers and split off his own project called OpenBSD . Since 2003 there is another BSD project with DragonFly BSD , a spin-off from FreeBSD. The operating system Mac OS X and its open source counterpart Darwin from Apple are also based in parts (which the “normal”, GUI- oriented users hardly notice) on BSD, especially FreeBSD. Through the continuation and further development of NeXTStep as Mac OS X, BSD again experienced a technical upswing and widespread use.

Similarities and differences between the BSDs

New developments and especially the numerous device drivers of a project are usually adopted by the others without any problems. The aim of all projects is to develop a free system, so only code compatible with the BSD license should flow into the actual system. However, the details of interpreting the term free software differ slightly.

NetBSD wants to support as many different hardware architectures and processors as possible. Of course it runs NetBSD is the slogan of the project. Particular attention is paid to the implementation of a system-wide, clean design and a clear structure. This includes the continuous creation and improvement of machine-independent interfaces, e.g. for device drivers, which enable the proverbial portability of NetBSD in the first place.

Due to its public relations is one of FreeBSD to the known most BSD variants. FreeBSD initially focused on PC hardware with Intel's 80386 processor. Ease of installation is a goal of the project so that non-experts can also use this system. The project therefore published installation CDs at an early stage. In addition to Intel and AMD processors, other processors such as Sun SPARC and Alpha are also supported.

OpenBSD is one of the main goals of creating the most secure free system. On the one hand, this includes proactive security, which means that code audits are used to detect errors as far as possible and eliminate them in advance. However, this by no means means that security is neglected with the other BSD variants. OpenBSD is a leader in the implementation of secure, encrypted transmission methods. IPsec support is part of it, as is an open implementation of the Secure Shell called OpenSSH .

Further BSD variants

BSD derivatives

Former BSD derivatives


Web links

Individual evidence

  1. ^ Sascha Kersken: IT manual for IT specialists . Galileo Computing, 2009, ISBN 978-3-8362-1420-9 .
  2. a b c d e f g h Finding Aid to the Berkeley Software Distribution Records . Online Archive of California (PDF; 20 kB).
  3. ^ AT&T Regents of the U. of California - The 1983 Educational License at Groklaw
  4. Unless otherwise stated, the statements in this section are based on the summary of the history of BSD by Marshall Kirk McKusick in the article Twenty Years of Berkeley Unix . ( Memento dated December 15, 2013 on WebCite ) O'Reilly Online Catalog 1999, ISBN 1-56592-582-3 .
  5. Andrew S. Tanenbaum : Modern Operating Systems . Pearson, 2009, ISBN 978-3-8273-7342-7 .
  6. a b Evi Nemeth: Handbook for Unix system administration . Pearson Deutschland GmbH, 2004, ISBN 978-3-8272-6787-0 , p. 39 ( limited preview in Google Book Search): "The AT&T source code licenses were very expensive for users outside the universities."
  7. a b USL vs. BSDI documents collection of the Bell Labs
  8. Jürgen Donauer: Orbis OS: Sony PlayStation 4 runs with modified FreeBSD 9., June 24, 2013, accessed on October 23, 2018 .
  9. ( Memento November 21, 2016 in the Internet Archive ) - Ubuntu on a FreeBSD core. The main developer is Jon Boden.
This version was added to the list of articles worth reading on August 18, 2005 .