FreeBSD is a free and open-source

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

descended from the Berkeley Software Distribution (BSD), which was based on

Research Unix The term "Research Unix" refers to early versions of the Unix operating system for DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Sciences Research Center (CSRC). History The term ''Resear ...

. 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 Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

, with two major differences in scope and licensing: FreeBSD maintains a complete system, i.e. the project delivers a

kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learn ...

, device drivers, userland utilities, and documentation, as opposed to Linux only delivering a

and drivers, and relying on third-parties for system software; FreeBSD

source code In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...

is generally released under a

permissive {{about, , the 1970 British film, Permissive (film), the grammatical mode, Permissive mood, the flavor of software license, permissive free software licence A permissive cell or host is one that allows a virus to circumvent its defenses and replica ...

BSD license BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...

, as opposed to the

copyleft Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...

GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general u ...

used by Linux. The FreeBSD project includes a

security" \n\n\nsecurity.txt is a proposed standard for websites' security information that is meant to allow security researchers to easily report security vulnerabilities. The standard prescribes a text file called \"security.txt\" in the well known locat ...

team overseeing all software shipped in the base distribution. A wide range of additional third-party

applications Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

may be installed from binary packages using the pkg

package management system A package manager or package-management system is a collection of software tools that automates the process of installing, upgrading, configuring, and removing computer programs for a computer in a consistent manner. A package manager deals w ...

or from source via

FreeBSD Ports The FreeBSD Ports collection is a package management system for the FreeBSD operating system, providing an easy and consistent way of installing software packages. As of February 2020, there are over 38,487 ports available in the collection. It has ...

, or by manually

compiling In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...

source code. Much of FreeBSD's

codebase In software development, a codebase (or code base) is a collection of source code used to build a particular software system, application, or software component. Typically, a codebase includes only human-written source code files; thus, a codeb ...

has become an integral part of other operating systems such as Darwin (the basis for

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also include ...

iPadOS iPadOS is a mobile operating system developed by Apple Inc. for its iPad line of tablet computers. It is a rebranded variant of iOS, the operating system used by Apple's iPhones, renamed to reflect the diverging features of the two product ...

watchOS watchOS is the operating system of the Apple Watch, developed by Apple Inc. It is based on iOS, the operating system used by the iPhone, and has many similar features. It was released on April 24, 2015, along with the Apple Watch, the only d ...

, and

tvOS tvOS (formerly known as Apple TV Software) is an operating system developed by Apple Inc. for the Apple TV, a digital media player. In the first-generation Apple TV, Apple TV Software was based on Mac OS X. Starting with the second-generation, ...

TrueNAS TrueNAS is the branding for a range of free and open-source network-attached storage (NAS) operating systems produced by iXsystems, and based on FreeBSD and Linux, using the OpenZFS file system. It is licensed under the terms of the BSD Lice ...

(an open-source

NAS Nas (born 1973) is the stage name of American rapper Nasir Jones. Nas, NaS, or NAS may also refer to: Aviation * Nasair, a low-cost airline carrier and subsidiary based in Eritrea * National Air Services, an airline in Saudi Arabia ** Nas Air ( ...

/ SAN operating system), and the system software for the

PlayStation 3 The PlayStation 3 (PS3) is a home video game console developed by Sony Computer Entertainment. The successor to the PlayStation 2, it is part of the PlayStation brand of consoles. It was first released on November 11, 2006, in Japan, November ...

and PlayStation 4 game consoles. The other BSD systems ( OpenBSD, NetBSD, and

DragonFly BSD DragonFly BSD is a free and open-source Unix-like operating system forked from FreeBSD 4.8. Matthew Dillon, an Amiga developer in the late 1980s and early 1990s and FreeBSD developer between 1994 and 2003, began working on DragonFly BSD in ...

) also contain a large amount of FreeBSD code, and vice-versa.

History

Background

In 1974, Professor

Bob Fabry Robert Samuel Fabry, as a student at the University of Chicago worked on COMIT II and MADBUG, an interactive debugger for MAD both on CTSS. Later while a computer science professor at the University of California, Berkeley, conceived of the id ...

of the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

, acquired a Unix source license from

AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile te ...

. Supported by funding from

DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...

, 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 The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...

virtual memory In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very ...

, and the

Berkeley Fast File System The Unix file system (UFS) is a family of file systems supported by many Unix and Unix-like operating systems. It is a distant descendant of the original filesystem used by Version 7 Unix. Design A UFS volume is composed of the following ...

. The BSD project was founded in 1976 by

Bill Joy William Nelson Joy (born November 8, 1954) is an American computer engineer and venture capitalist. He co-founded Sun Microsystems in 1982 along with Scott McNealy, Vinod Khosla, and Andy Bechtolsheim, and served as Chief Scientist and CTO at ...

. 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

. 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 William is a male given name of Germanic origin.Hanks, Hardcastle and Hodges, ''Oxford Dictionary of First Names'', Oxford University Press, 2nd edition, , p. 276. It became very popular in the English language after the Norman conquest of Engl ...

and

Lynne Jolitz Lynne Greer Jolitz (born June 30, 1961) is a figure in free software and founder of many startups in Silicon Valley. Together with her husband William, she created 386BSD, the first open-source Unix-based operating system for personal computers ...

wrote replacements for the six AT&T files, ported BSD to

Intel 80386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors386BSD. 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 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 Walnut Creek CDROM Inc. was an early provider of freeware, shareware, and free software on CD-ROMs. The company was founded in by Bob Bruce in Walnut Creek, California, in August 1991. It was one of the first commercial distributors of free softwar ...

, upon the suggestion of the two FreeBSD developers, agreed to release the operating system on

CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...

. In addition to that, the company employed

Jordan Hubbard Jordan K. Hubbard (born April 8, 1963) is an open source software developer, authoring software such as the Ardent Window Manager and various other open source tools and libraries before co-founding the FreeBSD project with Nate Williams and Rodn ...

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 iXsystems, Inc. is a privately owned American computer technology company based in San Jose, California that develops, sells and supports computing and storage products and services. Its principal products are customized open source FreeBSD dis ...

. Today, FreeBSD is used by many IT companies such as IBM,

Nokia Nokia Corporation (natively Nokia Oyj, referred to as Nokia) is a Finnish multinational corporation, multinational telecommunications industry, telecommunications, technology company, information technology, and consumer electronics corporatio ...

Juniper Networks Juniper Networks, Inc. is an American multinational corporation headquartered in Sunnyvale, California. The company develops and markets networking products, including routers, switches, network management software, network security product ...

, and

NetApp NetApp, Inc. is an American hybrid cloud data services and data management company headquartered in San Jose, California. It has ranked in the Fortune 500 from 2012–2021. Founded in 1992 with an IPO in 1995, NetApp offers cloud data service ...

to build their products. Certain parts of

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

Mac OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...

operating system are based on FreeBSD. Both the

and

Nintendo Switch The is a hybrid video game console developed by Nintendo and released worldwide in most regions on March 3, 2017. The console itself is a Tablet computer#Gaming tablet, tablet that can either be docking station, docked for use as a home video ...

operating system also borrow certain components from FreeBSD, while the PlayStation 4 operating system is derived from FreeBSD 9.

Netflix Netflix, Inc. is an American subscription video on-demand over-the-top streaming service and production company based in Los Gatos, California. Founded in 1997 by Reed Hastings and Marc Randolph in Scotts Valley, California, it offers a fil ...

WhatsApp WhatsApp (also called WhatsApp Messenger) is an internationally available freeware, cross-platform, centralized instant messaging (IM) and voice-over-IP (VoIP) service owned by American company Meta Platforms (formerly Facebook). It allows us ...

, and FlightAware are also examples of large, successful and heavily network-oriented companies which are running FreeBSD.

Lawsuit

386BSD and FreeBSD were both derived from BSD releases. In January 1992,

Berkeley Software Design Inc. Berkeley Software Design, Inc. (BSDI or, later, BSDi), was a corporation which developed, sold licenses for, and supported BSD/OS (originally known as BSD/386), a commercial and partially proprietary variant of the Berkeley Software Distribution, ...

(BSDi) started to release

BSD/386 BSD/OS (originally called BSD/386 and sometimes known as BSDi) is a discontinued proprietary version of the BSD operating system developed by Berkeley Software Design, Inc. (BSDi). BSD/OS had a reputation for reliability in server roles; the ren ...

, later called BSD/OS, an operating system similar to FreeBSD and based on 4.3BSD Net/2. AT&T filed a lawsuit against BSDi and alleged distribution of AT&T source code in violation of license agreements. The lawsuit was settled out of court and the exact terms were not all disclosed. The only one that became public was that BSDi would migrate their source base to the newer 4.4BSD-Lite2 sources. Although not involved in the litigation, it was suggested to FreeBSD that they should also move to 4.4BSD-Lite2. FreeBSD 2.0, which was released in November 1994, was the first version of FreeBSD without any code from AT&T.

Features

Use cases

FreeBSD contains a significant collection of server-related software in the base system and the ports collection, allowing FreeBSD to be configured and used as a

mail server Within the Internet email system, a message transfer agent (MTA), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX host ...

web server A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initiate ...

firewall Firewall may refer to: * Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts * Firewall (construction), a barrier inside a building, designed to limit the spr ...

, FTP server,

DNS server A name server refers to the server component of the Domain Name System (DNS), one of the two principal namespaces of the Internet. The most important function of DNS servers is the translation (resolution) of human-memorable domain names (example. ...

and a router, among other applications. FreeBSD can be installed on a regular desktop or a laptop. The

X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wit ...

is not installed by default, but is available in the FreeBSD ports collection.

Wayland (display server protocol) Wayland is a communication protocol that specifies the communication between a display server and its clients, as well as a C library implementation of that protocol. A display server using the Wayland protocol is called a ''Wayland compositor ...

is also available for FreeBSD (unofficially supported). A number of

desktop environment In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a graphica ...

s such as GNOME,

KDE KDE is an international free software community that develops free and open-source software. As a central development hub, it provides tools and resources that allow collaborative work on this kind of software. Well-known products include the ...

, and Xfce, as well as lightweight window managers such as Openbox,

Fluxbox Fluxbox is a stacking window manager for the X Window System, which started as a fork of Blackbox 0.61.1 in 2001, with the same aim to be lightweight. Its user interface has only a taskbar, a pop-up menu accessible by right-clicking on the des ...

dwm dwm is a minimalist dynamic window manager for the X Window System developed by Suckless that has influenced the development of several other X window managers, including xmonad and awesome. It is externally similar to wmii, but internally mu ...

, an
bspwm
are also available for FreeBSD. As of FreeBSD 12, support for a modern graphics stack is available via drm-kmod. A large number of wireless adapters are supported. FreeBSD releases installation images for supported platforms. Since FreeBSD 13 the focus has been on

x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...

and

aarch64 AArch64 or ARM64 is the 64-bit extension of the ARM architecture family. It was first introduced with the Armv8-A architecture. Arm releases a new extension every year. ARMv8.x and ARMv9.x extensions and features Announced in October 2011, AR ...

platforms which have Tier 1 support.

x86-32 IA-32 (short for "Intel Architecture, 32-bit", commonly called i386) is the 32-bit version of the x86 instruction set architecture, designed by Intel and first implemented in the 80386 microprocessor in 1985. IA-32 is the first incarnation o ...

is a Tier 1 platform in FreeBSD 12 but is a Tier 2 platform in FreeBSD 13. 32 bit ARM processors using armv6 or armv7 also have Tier 2 support. 64 bit versions of

PowerPC PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple Inc., App ...

and

RISC-V RISC-V (pronounced "risk-five" where five refers to the number of generations of RISC architecture that were developed at the University of California, Berkeley since 1981) is an open standard instruction set architecture (ISA) based on estab ...

are also supported. Interest in the RISC-V architecture has been growing. The

MIPS architecture MIPS (Microprocessor without Interlocked Pipelined Stages) is a family of reduced instruction set computer (RISC) instruction set architectures (ISA)Price, Charles (September 1995). ''MIPS IV Instruction Set'' (Revision 3.2), MIPS Technologies, ...

port has been marked for deprecation and there is no image for any currently supported version. FreeBSD 12 supports

SPARC SPARC (Scalable Processor Architecture) is a reduced instruction set computer (RISC) instruction set architecture originally developed by Sun Microsystems. Its design was strongly influenced by the experimental Berkeley RISC system developed ...

but there is no image for FreeBSD 13.

Networking

FreeBSD's TCP/IP stack is based on the

4.2BSD The History of the Berkeley Software Distribution begins in the 1970s. 1BSD (PDP-11) The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the operating system, allowing researchers at universities to modify a ...

implementation of TCP/IP which greatly contributed to the widespread adoption of these protocols. FreeBSD also supports

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

SCTP The Stream Control Transmission Protocol (SCTP) is a computer networking communications protocol in the transport layer of the Internet protocol suite. Originally intended for Signaling System 7 (SS7) message transport in telecommunication, the p ...

IPSec In computing, Internet Protocol Security (IPsec) is a secure network protocol suite that authenticates and encrypts packets of data to provide secure encrypted communication between two computers over an Internet Protocol network. It is used in ...

, and wireless networking (

Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wav ...

). The IPv6 and IPSec stacks were taken from the

KAME project The KAME project, a sub-project of the WIDE Project, was a joint effort of six organizations in Japan which aimed to provide a free IPv6 and IPsec (for both IPv4 and IPv6) protocol stack implementation for variants of the BSD Unix computer opera ...

. Prior to version 11.0, FreeBSD supported

IPX Internetwork Packet Exchange (IPX) is the network layer protocol in the IPX/SPX protocol suite. IPX is derived from Xerox Network Systems' IDP. It also has the ability to act as a transport layer protocol. The IPX/SPX protocol suite was very p ...

and AppleTalk protocols, but they are considered old and have now been dropped. As of FreeBSD 5.4, support for the

Common Address Redundancy Protocol The Common Address Redundancy Protocol or CARP is a computer networking protocol which allows multiple hosts on the same local area network to share a set of IP addresses. Its primary purpose is to provide failover redundancy, especially when used ...

(CARP) was imported from the OpenBSD project. CARP allows multiple nodes to share a set of IP addresses, so if one of the nodes goes down, other nodes still can serve the requests.

Storage

FreeBSD has several unique features related to storage.

Soft updates Soft updates is an approach to maintaining file system meta-data integrity in the event of a crash or power outage. Soft updates work by tracking and enforcing dependencies among updates to file system meta-data. Soft updates are an alternative t ...

can protect the consistency of the UFS filesystem (widely used on the BSDs) in the event of a system crash. Filesystem snapshots allow an image of a UFS filesystem at an instant in time to be efficiently created. Snapshots allow reliable backup of a live filesystem.

GEOM GEOM is the main storage framework for the FreeBSD operating system. It is available in FreeBSD 5.0 and later releases, and provides a standardized way to access storage layers. GEOM is modular and allows for ''geom modules'' to connect to the fra ...

is a modular framework that provides

RAID Raid, RAID or Raids may refer to: Attack * Raid (military), a sudden attack behind the enemy's lines without the intention of holding ground * Corporate raid, a type of hostile takeover in business * Panty raid, a prankish raid by male college ...

(levels 0, 1, 3 currently),

full disk encryption Disk encryption is a technology which protects information by converting it into unreadable code that cannot be deciphered easily by unauthorized people. Disk encryption uses disk encryption software or hardware to encrypt every bit of data that g ...

, journaling, concatenation, caching, and access to network-backed storage. GEOM allows building of complex storage solutions combining ("chaining") these mechanisms. FreeBSD provides two frameworks for data encryption:

GBDE GBDE, standing for GEOM Based Disk Encryption, is a block device-layer disk encryption system written for FreeBSD, initially introduced in version 5.0. It is based on the GEOM disk framework. GBDE was designed and implemented by Poul-Henning Kamp an ...

and Geli. Both GBDE and Geli operate at the disk level. GBDE was written by

Poul-Henning Kamp Poul-Henning Kamp (; born 1966) is a Danish computer software developer known for work on various projects including FreeBSD and Varnish. He currently resides in Slagelse, Denmark. Involvement in the FreeBSD project Poul-Henning Kamp has been c ...

and is distributed under the two-clause BSD license. Geli is an alternative to GBDE that was written by Pawel Jakub Dawidek and first appeared in FreeBSD 6.0. From 7.0 onward, FreeBSD supports the

ZFS ZFS (previously: Zettabyte File System) is a file system with volume management capabilities. It began as part of the Sun Microsystems Solaris operating system in 2001. Large parts of Solaris – including ZFS – were published under an ope ...

filesystem. ZFS was previously an open-source filesystem that was first developed by

Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the ...

, but when Oracle acquired Sun, ZFS became a proprietary product. However, the FreeBSD project is still developing and improving its ZFS implementation via the

OpenZFS OpenZFS is a free and open-source storage platform licensed under CDDL that encompasses the functionality of traditional filesystems and logical volume manager. It includes protection against data corruption, support for high storage capaciti ...

project.

Security

FreeBSD provides several security-related features including

access-control list In computer security, an access-control list (ACL) is a list of permissions associated with a system resource (object). An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on give ...

s (ACLs), security event auditing, extended file system attributes,

mandatory access control In computer security, mandatory access control (MAC) refers to a type of access control by which the operating system or database constrains the ability of a ''subject'' or ''initiator'' to access or generally perform some sort of operation on a ...

s (MAC) and fine-grained capabilities. These security enhancements were developed by the TrustedBSD project. The project was founded by Robert Watson with the goal of implementing concepts from the Common Criteria for Information Technology Security Evaluation and the Orange Book. This project is ongoing and many of its extensions have been integrated into FreeBSD. The project is supported by a variety of organizations, including the DARPA, NSA, Network Associates Laboratories, Safeport Network Services, the University of Pennsylvania, Yahoo!, McAfee Research, SPARTA, Apple Computer, nCircle Network Security, Google, the University of Cambridge Computer Laboratory, and others. The project has also ported the

NSA The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collecti ...

FLASK Flask may refer to: Container * Hip flask, a small container used to carry a small amount of liquid * Laboratory flask, laboratory glassware for holding larger volumes than simple test tubes ** Erlenmeyer flask, a common laboratory flask wit ...

/TE implementation from

SELinux Security-Enhanced Linux (SELinux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including mandatory access controls (MAC). SELinux is a set of kernel modifications and user-space ...

to FreeBSD. Other work includes the development of OpenBSM, an open-source implementation of Sun's Basic Security Module (BSM)

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

and audit log file format, which supports an extensive security audit system. This was shipped as part of FreeBSD 6.2. Other infrastructure work in FreeBSD performed as part of the TrustedBSD Project has included GEOM and OpenPAM. Most components of the TrustedBSD project are eventually folded into the main sources for FreeBSD. In addition, many features, once fully matured, find their way into other operating systems. For example,

OpenPAM OpenPAM is a BSD-licensed implementation of PAM used by FreeBSD, NetBSD, DragonFly BSD and macOS (starting with Snow Leopard), and offered as an alternative to Linux PAM in certain Linux distributions. OpenPAM was developed for the FreeBSD ...

has been adopted by NetBSD. Moreover, the TrustedBSD MAC Framework has been adopted by

for

. FreeBSD ships with three different firewall packages: IPFW, pf and IPFilter. IPFW is FreeBSD's native firewall. pf was taken from OpenBSD and IPFilter was ported to FreeBSD by Darren Reed. Taken from OpenBSD, the OpenSSH program was included in the default install. OpenSSH is a free implementation of the SSH protocol and is a replacement for telnet. Unlike telnet, OpenSSH encrypts all information (including usernames and passwords). In November 2012, The FreeBSD Security Team announced that hackers gained unauthorized access on two of the project's servers. These servers were turned off immediately. More research demonstrated that the first unauthorized access by hackers occurred on 19 September. Apparently hackers gained access to these servers by stealing Secure Shell#Key management, SSH keys from one of the developers, not by exploiting a bug in the operating system itself. These two hacked servers were part of the infrastructure used to build third-party software packages. The FreeBSD Security Team checked the integrity of the binary packages and announced that no unauthorized changes were made to the binary packages, but stated that they could not guarantee the integrity of packages that were downloaded between 19 September and 11 November.

Portability

FreeBSD has been ported to a variety of instruction set architectures. The FreeBSD project organizes architectures into tiers that characterize the level of support provided. Tier 1 architectures are mature and fully supported, e.g. it is the only tier "supported by the security officer". Tier 3 architectures are experimental or are no longer under active development and Tier 4 architectures have no support at all. , FreeBSD has been ported to the following architectures: The 32-bit ARM (including OTG) and MIPS support is mostly aimed at embedded systems (AArch64, ARM64 is also aimed at servers), however FreeBSD/ARM runs on a number of single-board computers, including the BeagleBone Black, Raspberry Pi and Wandboard.

Hardware compatibility

Supported devices are listed in the FreeBSD 12.1-RELEASE Hardware Notes. The document describes the devices currently known to be supported by FreeBSD. Other configurations may also work, but simply have not been tested yet. Rough automatically extracted lists of supported device ids are available in a third party repository. In 2020, a new project was introduced to automatically collect information about tested hardware configurations.

Third-party software

FreeBSD has a software repository of over 30,000 applications that are developed by third parties. Examples include: windowing systems, web browsers, email clients, Productivity software, office suites and so forth. In general, the project itself does not develop this software, only the framework to allow these programs to be installed, which is known as the Ports collection. Applications may either be Compiler, compiled from Source code, source ("ports"), provided their licensing terms allow this, or downloaded as precompiled binaries ("packages"). The Ports collection supports the current and stable branches of FreeBSD. Older releases are not supported and may or may not work correctly with an up-to-date Ports collection. Ports use make (software), Makefiles to automatically fetch the desired application's

, either from a local or remote Digital library, repository, unpack it on the system, apply patches to it and compile it. Depending on the size of the source code, compiling can take a long time, but it gives the user more control over the process and its result. Most ports also have package counterparts (i.e. precompiled binaries), giving the user a choice. Although this method is faster, the user has fewer customization options. FreeBSD version 10.0 introduced the package manager pkg as a replacement for the previously used package tools. It is functionally similar to Advanced Packaging Tool, apt and Yellowdog Updater, Modified, yum in Linux distributions. It allows for installation, upgrading and removal of both ports and packages. In addition to pkg, PackageKit can also be used to access the Ports collection.

Jails

First introduced in FreeBSD version 4, jails are a security mechanism and an implementation of operating-system-level virtualization that enables the user to run multiple instances of a guest operating system on top of a FreeBSD host. It is an enhanced version of the traditional chroot mechanism. A process that runs within such a jail is unable to access the resources outside of it. Every jail has its own hostname and IP address. It is possible to run multiple jails at the same time, but the kernel is shared among all of them. Hence only software supported by the FreeBSD kernel can be run within a jail.

Virtualization

bhyve, a new virtualization solution, was introduced in FreeBSD 10.0. bhyve allows a user to run a number of guest operating systems (FreeBSD, OpenBSD,

, and Microsoft Windows) simultaneously. Other operating systems such as Illumos are planned. bhyve was written by Neel Natu and Peter Grehan and was announced in the 2011 BSDCan conference for the first time. The main difference between bhyve and FreeBSD jails is that jails are an operating system-level virtualization and therefore limited to only FreeBSD guests; but bhyve is a type 2 hypervisor and is not limited to only FreeBSD guests. For comparison, bhyve is a similar technology to Kernel-based Virtual Machine, KVM whereas jails are closer to LXC, LXC containers or Solaris Containers, Solaris Zones. Amazon EC2 AMI instances are also supported via amazon-ssm-agent Since FreeBSD 11.0, there has been support for running as the Dom0 privileged domain for the Xen type 1 hypervisor. Support for running as DomU (guest) has been available since FreeBSD 8.0. VirtualBox (without the closed-source VirtualBox#VirtualBox Extension Pack, Extension Pack) and QEMU are available on FreeBSD.

OS compatibility layers

Most software that runs on

can run on FreeBSD using an optional built-in compatibility layer. Hence, most Linux binaries can be run on FreeBSD, including some proprietary applications distributed only in binary form. This compatibility layer is not an Emulator, emulation; Linux's system call interface is implemented in the FreeBSD's kernel and hence, Linux executable, executable images and shared libraries are treated the same as FreeBSD's native executable images and shared libraries. Additionally, FreeBSD provides compatibility layers for several other

s, in addition to Linux, such as BSD/OS and SVR4, however, it is more common for users to compile those programs directly on FreeBSD. No noticeable performance penalty over native FreeBSD programs has been noted when running Linux binaries, and, in some cases, these may even perform more smoothly than on Linux. However, the layer is not altogether seamless, and some Linux binaries are unusable or only partially usable on FreeBSD. There is support for system calls up to version 2.6.18, available since . As of release 10.3, FreeBSD can run 64-bit Linux binaries. FreeBSD has implemented a number of Microsoft Windows native Network Driver Interface Specification, NDIS kernel interfaces to allow FreeBSD to run (otherwise) Windows-only network drivers. The Wine (software), Wine compatibility layer, which allows the running of many Windows applications, especially games, without a (licensed) copy of Microsoft Windows, is available for FreeBSD.

Kernel

FreeBSD's kernel provides support for some essential tasks such as managing processes, communication, booting and filesystems. FreeBSD has a monolithic kernel, monolithic kernel, with a modular design. Different parts of the kernel, such as drivers, are designed as modules. The user can load and unload these modules at any time. ULE scheduler, ULE is the default scheduling (computing), scheduler in FreeBSD since version 7.1, it supports Symmetric multiprocessor system, SMP and Simultaneous multithreading, SMT. The FreeBSD kernel has also a scalable event notification interface, named kqueue. It has been ported to other BSD-derivatives such as OpenBSD and NetBSD. Kernel threading was introduced in FreeBSD 5.0, using an Thread (computing)#M:N (hybrid threading), M:N threading model. This model works well in theory, but it is hard to implement and few operating systems support it. Although FreeBSD's implementation of this model worked, it did not perform well, so from version 7.0 onward, FreeBSD started using a Thread (computing)#1:1 (kernel-level threading), 1:1 threading model, called libthr.

Documentation and support

FreeBSD's documentation consists of its handbooks, manual pages, mailing list archives, FAQs and a variety of articles, mainly maintained by The FreeBSD Documentation Project. FreeBSD's documentation is translated into several languages. All official documentation is released under the FreeBSD Documentation License, "a permissive non-copyleft free documentation license that is compatible with the GNU FDL". FreeBSD's documentation is described as "high-quality". The FreeBSD project maintains a variety of mailing lists. Among the most popular mailing lists are FreeBSD-questions (general questions) and FreeBSD-hackers (a place for asking more technical questions). Since 2004, the New York City BSD Users Group database provides dmesg information from a collection of computers (laptops, workstations, single-board computers, embedded systems, virtual machines, etc.) running FreeBSD.

Installers

From version 2.0 to 8.4, FreeBSD used the sysinstall program as its main installer. It was written in C (programming language), C by

. It uses a text user interface, and is divided into a number of menus and screens that can be used to configure and control the installation process. It can also be used to install Ports and Packages as an alternative to the command-line interface. The sysinstall utility is now considered deprecated in favor of bsdinstall, a new installer which was introduced in FreeBSD 9.0. bsdinstall is "a lightweight replacement for sysinstall" that was written in sh. According to OSNews, "It has lost some features while gaining others, but it is a much more flexible design, and will ultimately be significant improvement".

Shell

The default FreeBSD shell is the tcsh shell for root, and the Almquist shell (sh) for regular users. The default scripting shell is the Almquist shell.

Development

FreeBSD is developed by a volunteer team located around the world. The developers use the Internet for all communication and many have not met each other in person. In addition to local user groups sponsored and attended by users, an annual conference, called BSDcon, is held by USENIX. BSDcon is not FreeBSD-specific so it deals with the technical aspects of all BSD-derived operating systems, including OpenBSD and NetBSD. In addition to BSDcon, three other annual conferences, EuroBSDCon, AsiaBSDCon and BSDCan take place in Europe, Japan and Canada respectively.

Governance structure

The FreeBSD Project is run by around 500 committers or developers who have commit access to the master source code repositories and can develop, debug or enhance any part of the system. Most of the developers are volunteers and few developers are paid by some companies. There are several kinds of committers, including source committers (base operating system), doc committers (documentation and website authors) and ports (third-party application porting and infrastructure). Every two years the FreeBSD committers select a 9-member FreeBSD Core Team, which is responsible for overall project direction, setting and enforcing project rules and approving new committers, or the granting of commit access to the source code repositories. A number of responsibilities are officially assigned to other development teams by the FreeBSD Core Team, for example, responsibility for managing the ports collection is delegated to the Ports Management Team. In addition to developers, FreeBSD has thousands of "contributors". Contributors are also volunteers outside of the FreeBSD project who submit patches for consideration by committers, as they don't have direct access to FreeBSD's source code repository. Committers then evaluate contributors' submissions and decide what to accept and what to reject. A contributor who submits high-quality patches is often asked to become a committer.

Branches

FreeBSD software developer, developers maintain at least two branches of simultaneous development. The ''-CURRENT'' branch always represents the "bleeding edge" of FreeBSD development. A ''-STABLE'' branch of FreeBSD is created for each major version number, from which -RELEASE is cut about once every 4–6 months. If a feature is sufficiently stable and mature it will likely be backported (''MFC'' or ''Merge from CURRENT'' in FreeBSD developer slang) to the ''-STABLE'' branch.

Foundation

FreeBSD development is supported in part by the FreeBSD Foundation. The foundation is a non-profit organization that accepts donations to fund FreeBSD development. Such funding has been used to sponsor developers for specific activities, purchase hardware and network infrastructure, provide travel grants to developer summits, and provide legal support to the FreeBSD project. In November 2014, the FreeBSD Foundation received US$1 million donation from Jan Koum, co-founder and CEO of

the largest single donation to the Foundation since its inception. In December 2016, Jan Koum donated another $500,000. Jan Koum himself is a FreeBSD user since the late 1990s and WhatsApp uses FreeBSD on its servers.

License

FreeBSD is released under a variety of open-source licenses. The kernel code and most newly created code are released under the two-clause

which allows everyone to use and redistribute FreeBSD as they wish. This license was approved by Free Software Foundation and Open Source Initiative as a Free Software and Open Source license respectively. Free Software Foundation described this license as "a lax, permissive non-copyleft free software license, compatible with the GNU GPL". There are parts released under three- and four-clause BSD licenses, as well as the Beerware license. Some device drivers include a binary blob, such as the Atheros Hardware abstraction layer, HAL of FreeBSD versions before 7.2. Some of the code contributed by other projects is licensed under GNU General Public License, GPL, GNU Lesser General Public License, LGPL, Common Development and Distribution License, CDDL and ISC license, ISC. All the code licensed under

and CDDL is clearly separated from the code under liberal licenses, to make it easy for users such as embedded device manufacturers to use only permissive free software licenses. ClangBSD aims to replace some

dependencies in the FreeBSD base system by replacing the GNU compiler collection with the BSD-licensed LLVM/Clang compiler. ClangBSD became self-hosting on 16 April 2010.

Logo

For many years FreeBSD's logo was the generic BSD Daemon, also called ''Beastie'', a distorted pronunciation of ''BSD''. However, Beastie was not unique to FreeBSD. First appearing in 1976 on Unix T-shirts purchased by Bell Labs, the more popular versions of the BSD daemon were drawn by animation director John Lasseter beginning in 1984. Several FreeBSD-specific versions were later drawn by Tatsumi Hosokawa. In lithographic terms, the Lasseter graphic is not line art and often requires a screened, four-color Photo-offset, photo offset printing process for faithful reproduction on physical surfaces such as paper. Also, the BSD daemon was thought to be too graphically detailed for smooth size scaling and aesthetically over-dependent on multiple color gradations, making it hard to reliably reproduce as a simple, standardized logo in only two or three colors, much less in monochrome. Because of these worries, a competition was held and a new logo designed by Anton K. Gural, still echoing the BSD daemon, was released on 8 October 2005. However, it was announced by Robert Watson that the FreeBSD project is "seeking a new logo, but not a new mascot" and that the FreeBSD project would continue to use Beastie as its mascot. The name "FreeBSD" was coined by David Greenman on 19 June 1993, other suggested names were "BSDFree86" and "Free86BSD". FreeBSD's slogan, "The Power to Serve", is a trademark of The FreeBSD Foundation.

Derivatives

There are a number of software distributions based on FreeBSD. Notable derivatives include: * DesktopBSD (desktop-oriented operating system, originally based on KDE) *

(for network-attached storage devices) * FreeSBIE (live CD) * GhostBSD (MATE (software), MATE-based distribution, which also offers other desktop environments) * MidnightBSD * NanoBSD * PicoBSD * IntelliStar (satellite system that runs TV programs such as Weatherscan and Local On The 8s) * m0n0wall (firewall) * OpenServer 10 (server) * OPNsense (firewall) * pfSense (firewall) * TrueOS, previously known as PC-BSD (aimed at home users and workstations, but with a FreeNAS-like server version and TrueOS pico for ARM architecture, ARM 32-bit embedded devices) * TrustedBSD * XigmaNAS (for network-attached storage devices) All these distributions have no or only minor changes when compared with the original FreeBSD base system. The main difference to the original FreeBSD is that they come with pre-installed and pre-configured software for specific use cases. This can be compared with

distributions, which are all binary compatible because they use the same kernel and also use the same basic tools, compilers, and libraries while coming with different applications, configurations, and branding. Besides these distributions, there are some independent operating systems based on FreeBSD.

is a fork from FreeBSD 4.8 aiming for a different multiprocessor synchronization strategy than the one chosen for FreeBSD 5 and development of some microkernel features. It does not aim to stay compatible with FreeBSD and has huge differences in the kernel and basic userland. MidnightBSD is a fork of FreeBSD 6.1 borrowing heavily from NeXTSTEP, particularly in the user interface department. Darwin, the core of

, includes a virtual file system and network stack derived from those of FreeBSD, and components of its userspace are also FreeBSD-derived. Some subscription services that are directly based on FreeBSD are: *

processes 2 million concurrent TCP connections per server. Embedded devices and embedded device operating systems based on FreeBSD include: * Juniper Networks, Juniper's JUNOS router operating system. * EMC Isilon's OneFS distributed file system, OneFS operating system. *

's Data ONTAP 8.x and the now-superseded ONTAP GX (only as a loader for proprietary kernel-space module). *

's Open Connect Appliance to handle content delivery. * The PlayStation 4 ("PlayStation 4 system software, Orbis OS") * Panasas' PanFS parallel file system * pfSense, an open-source firewall, router and security appliance operating system.

Version history

References

Citations

Sources

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External links

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FreeBSD
on DistroWatch
FreeBSD on OpenSourceFeed Gallery
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