FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD). The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular open-source BSD operating system, accounting for more than three-quarters of all installed and permissively licensed BSD systems.
FreeBSD has similarities with Linux, with two major differences in scope and licensing: FreeBSD maintains a complete system, i.e. the project delivers a kernel, device drivers, userland utilities, and documentation, as opposed to Linux only delivering a kernel and drivers, and relying on third-parties for system software; FreeBSD source code is generally released under a permissive BSD license, as opposed to the copyleft GPL used by Linux.
The FreeBSD project includes a security team overseeing all software shipped in the base distribution. A wide range of additional third-party applications may be installed from binary packages using the pkg package management system or from source via FreeBSD Ports, or by manually compiling source code.
Much of FreeBSD's codebase has become an integral part of other operating systems such as Darwin (the basis for macOS, iOS, iPadOS, watchOS, and tvOS), TrueNAS (an open-source NAS/SAN operating system), and the system software for the PlayStation 3 and PlayStation 4 game consoles. The other BSD systems (OpenBSD, NetBSD, and DragonFly BSD) also contain a large amount of FreeBSD code, and vice-versa.
History
Background
In 1974, Professor Bob Fabry of the University of California, Berkeley, acquired a Unix source license from AT&T. Supported by funding from DARPA, the Computer Systems Research Group started to modify and improve AT&T Research Unix. They called this modified version "Berkeley Unix" or "Berkeley Software Distribution" (BSD), implementing features such as TCP/IP, virtual memory, and the Berkeley Fast File System. The BSD project was founded in 1976 by Bill Joy. But since BSD contained code from AT&T Unix, all recipients had to first get a license from AT&T in order to use BSD.
In June 1989, "Networking Release 1" or simply Net-1 – the first public version of BSD – was released. After releasing Net-1, Keith Bostic, a developer of BSD, suggested replacing all AT&T code with freely-redistributable code under the original BSD license. Work on replacing AT&T code began and, after 18 months, much of the AT&T code was replaced. However, six files containing AT&T code remained in the kernel. The BSD developers decided to release the "Networking Release 2" (Net-2) without those six files. Net-2 was released in 1991.
Birth of FreeBSD
In 1992, several months after the release of Net-2, William and Lynne Jolitz wrote replacements for the six AT&T files, ported BSD to Intel 80386-based microprocessors, and called their new operating system 386BSD. They released 386BSD via an anonymous FTP server. The development flow of 386BSD was slow, and after a period of neglect, a group of 386BSD users including Nate Williams, Rod Grimes and Jordan Hubbard decided to branch out on their own so that they could keep the operating system up to date. On 19 June 1993, the name FreeBSD was chosen for the project. The first version of FreeBSD was released in November 1993.
In the early days of the project's inception, a company named Walnut Creek CDROM, upon the suggestion of the two FreeBSD developers, agreed to release the operating system on CD-ROM. In addition to that, the company employed Jordan Hubbard and David Greenman, ran FreeBSD on its servers, sponsored FreeBSD conferences and published FreeBSD-related books, including The Complete FreeBSD by Greg Lehey. By 1997, FreeBSD was Walnut Creek's "most successful product". The company later renamed itself to The FreeBSD Mall and later iXsystems.
Today, FreeBSD is used by many IT companies such as IBM, Nokia, Juniper Networks, and NetApp to build their products. Certain parts of Apple's Mac OS X operating system are based on FreeBSD. Both the PlayStation 3 and Nintendo Switch operating system also borrow certain components from FreeBSD, while the PlayStation 4 operating system is derived from FreeBSD 9. Netflix, WhatsApp, and FlightAware are also examples of large, successful and heavily network-oriented companies which are running FreeBSD.