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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 daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. 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, whi ...
, 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 Documentation is any communicable material that is used to describe, explain or instruct regarding some attributes of an object, system or procedure, such as its parts, assembly, installation, maintenance and use. As a form of knowledge manageme ...
, as opposed to Linux only delivering a kernel 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 ...
is generally released under a permissive BSD license, 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 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 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, 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 tha ...
source code. Much of FreeBSD's codebase 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 la ...
, iOS, iPadOS, watchOS, and tvOS), TrueNAS (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 Interactive Entertainment, Sony Computer Entertainment. The successor to the PlayStation 2, it is part of the PlayStation brand of consoles. It was first released on Novemb ...
and
PlayStation 4 The PlayStation 4 (PS4) is a home video game console developed by Sony Interactive Entertainment. Announced as the successor to the PlayStation 3 in February 2013, it was launched on November 15, 2013, in North America, November 29, 2013 i ...
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 ...
) 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 i ...
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 un ...
, 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 ...
. 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 A ...
, 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 su ...
,
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 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 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 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 Rodne ...
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 Nokia Corporation (natively Nokia Oyj, referred to as Nokia) is a Finnish multinational telecommunications, information technology, and consumer electronics corporation, established in 1865. Nokia's main headquarters are in Espoo, Finland, i ...
, Juniper Networks, 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 trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
's
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 lap ...
operating system are based on FreeBSD. Both the
PlayStation 3 The PlayStation 3 (PS3) is a home video game console developed by Sony Interactive Entertainment, Sony Computer Entertainment. The successor to the PlayStation 2, it is part of the PlayStation brand of consoles. It was first released on Novemb ...
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 that can either be docked for use as a home console or used as a portable device, making it a ...
operating system also borrow certain components from FreeBSD, while the
PlayStation 4 The PlayStation 4 (PS4) is a home video game console developed by Sony Interactive Entertainment. Announced as the successor to the PlayStation 3 in February 2013, it was launched on November 15, 2013, in North America, November 29, 2013 i ...
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 ...
,
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 use ...
, 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. (BSDi) started to release BSD/386, 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 ho ...
, web server,
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 spre ...
, FTP server, DNS server 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 wi ...
is not installed by default, but is available in the FreeBSD ports collection. Wayland (display server protocol) 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 grap ...
s such as GNOME, KDE, and Xfce, as well as lightweight window managers such as Openbox, Fluxbox,
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 ...
, 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 and aarch64 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 incarnatio ...
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– IBM– ...
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 est ...
are also supported. Interest in the RISC-V architecture has been growing. The MIPS architecture 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 develope ...
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 an ...
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 communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. I ...
, SCTP,
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 waves ...
). The IPv6 and IPSec stacks were taken from the KAME project. Prior to version 11.0, FreeBSD supported IPX 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 use ...
(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 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 (levels 0, 1, 3 currently), full disk encryption, 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 and Geli. Both GBDE and Geli operate at the disk level. GBDE was written by Poul-Henning Kamp 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 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, t ...
, but when
Oracle An oracle is a person or agency considered to provide wise and insightful counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. As such, it is a form of divination. Description The word ...
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 capacitie ...
project.


Security

FreeBSD provides several security-related features including access-control lists (ACLs), security event auditing, extended file system attributes, mandatory access controls (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, collec ...
's FLASK/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 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 has been adopted by NetBSD. Moreover, the TrustedBSD MAC Framework has been adopted by
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
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 la ...
. 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 Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet control i ...
. 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 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 architecture In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ...
s. 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 ( 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 system In computing, a windowing system (or window system) is software that manages separately different parts of display screens. It is a type of graphical user interface (GUI) which implements the WIMP ( windows, icons, menus, pointer) paradigm f ...
s,
web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...
s, email clients,
office suites Productivity software (also called personal productivity software or office productivity software) is application software used for producing information (such as documents, presentations, worksheets, databases, charts, graphs, digital paintin ...
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
compiled 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 tha ...
from 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
Makefile In software development, Make is a build automation tool that automatically builds executable programs and libraries from source code by reading files called ''Makefiles'' which specify how to derive the target program. Though integrated ...
s to automatically fetch the desired application's
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 ...
, either from a local or remote 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 apt and yum in Linux distributions. It allows for installation, upgrading and removal of both ports and packages. In addition to pkg,
PackageKit PackageKit is a free and open-source suite of software applications designed to provide a consistent and high-level front end for a number of different package management systems. PackageKit was created by Richard Hughes in 2007, and first int ...
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 A chroot on Unix and Unix-like operating systems is an operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name (and therefore normal ...
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 An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...
. 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,
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, whi ...
, and
Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
) 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 OS-level virtualization is an operating system (OS) paradigm in which the kernel allows the existence of multiple isolated user space instances, called ''containers'' ( LXC, Solaris containers, Docker, Podman), ''zones'' (Solaris containers), ' ...
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 KVM whereas jails are closer to LXC containers or
Solaris Zones Solaris Containers (including Solaris Zones) is an implementation of operating system-level virtualization technology for x86 and SPARC systems, first released publicly in February 2004 in build 51 beta of Solaris 10, and subsequently in the fi ...
.
Amazon EC2 Amazon Elastic Compute Cloud (EC2) is a part of Amazon.com's cloud-computing platform, Amazon Web Services (AWS), that allows users to rent virtual computers on which to run their own computer applications. EC2 encourages scalable deployment of ...
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 Extension Pack) and QEMU are available on FreeBSD.


OS compatibility layers

Most software that runs on
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, whi ...
can run on FreeBSD using an optional built-in
compatibility layer In software engineering, a compatibility layer is an interface that allows binaries for a legacy or foreign system to run on a host system. This translates system calls for the foreign system into native system calls for the host system. With s ...
. Hence, most Linux binaries can be run on FreeBSD, including some proprietary applications distributed only in binary form. This compatibility layer is not an emulation; Linux's system call interface is implemented in the FreeBSD's kernel and hence, Linux executable images and
shared libraries In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and ...
are treated the same as FreeBSD's native executable images and shared libraries. Additionally, FreeBSD provides
compatibility layer In software engineering, a compatibility layer is an interface that allows binaries for a legacy or foreign system to run on a host system. This translates system calls for the foreign system into native system calls for the host system. With s ...
s for several other
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 daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
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 Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
native NDIS kernel interfaces to allow FreeBSD to run (otherwise) Windows-only network drivers. The
Wine Wine is an alcoholic drink typically made from Fermentation in winemaking, fermented grapes. Yeast in winemaking, Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different ...
compatibility layer, which allows the running of many Windows applications, especially games, without a (licensed) copy of
Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
, 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, 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 Ule is a German surname. It may refer to: *Ernst Heinrich Georg Ule (1854–1915), German botanist and explorer *Otto Eduard Vincenz Ule (1820–1876), German natural science writer *Wilhelm Ule Wilhelm Ule, sometimes referred to as Willi Ule (9 ...
is the default scheduler in FreeBSD since version 7.1, it supports SMP and SMT. The FreeBSD kernel has also a scalable event notification interface, named
kqueue Kqueue is a scalable event notification interface introduced in FreeBSD 4.1 in July 2000, also supported in NetBSD, OpenBSD, DragonFly BSD, and macOS. Kqueue was originally authored in 2000 by Jonathan Lemon, then involved with the FreeBSD C ...
. It has been ported to other BSD-derivatives such as OpenBSD and NetBSD. Kernel threading was introduced in FreeBSD 5.0, using an 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 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 dmesg (''diagnostic messages'') is a command on most Unix-like operating systems that prints the message buffer of the kernel. The output includes messages produced by the device drivers. Command On many Unix-like systems, the boot process g ...
information from a collection of computers (
laptop A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...
s,
workstation A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating systems. The term ''workst ...
s, single-board computers,
embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded ...
s, 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 by
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 Rodne ...
. 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 A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
. 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 OSNews is a computing online newspaper. It originally focused on operating systems and their related technologies that launched in 1997, but is now aggregating consumer electronics news. The content is managed by a group of editors and the owne ...
, "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 Almquist shell (also known as A Shell, ash and sh) is a lightweight Unix shell originally written by Kenneth Almquist in the late 1980s. Initially a clone of the System V.4 variant of the Bourne shell, it replaced the original Bourne shell in th ...
(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 The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...
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 Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
and
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...
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 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
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 use ...
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 BSD license which allows everyone to use and redistribute FreeBSD as they wish. This license was approved by
Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed under copyleft ( ...
and
Open Source Initiative The Open Source Initiative (OSI) is the steward of the Open Source Definition, the set of rules that define open source software. It is a California public-benefit nonprofit corporation, with 501(c)(3) tax-exempt status. The organization wa ...
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 Qualcomm Atheros is a developer of semiconductor Integrated circuit, chips for Computer network, network communications, particularly wireless chipsets. Founded under the name T-Span Systems in 1998 by experts in signal processing and VLSI desig ...
HAL HAL may refer to: Aviation * Halali Airport (IATA airport code: HAL) Halali, Oshikoto, Namibia * Hawaiian Airlines (ICAO airline code: HAL) * HAL Airport, Bangalore, India * Hindustan Aeronautics Limited an Indian aerospace manufacturer of figh ...
of FreeBSD versions before 7.2. Some of the code contributed by other projects is licensed under GPL, LGPL,
CDDL The Common Development and Distribution License (CDDL) is a free and open-source software license, produced by Sun Microsystems, based on the Mozilla Public License (MPL). Files licensed under the CDDL can be combined with files licensed under ...
and ISC. All the code licensed under GPL and
CDDL The Common Development and Distribution License (CDDL) is a free and open-source software license, produced by Sun Microsystems, based on the Mozilla Public License (MPL). Files licensed under the CDDL can be combined with files licensed under ...
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 license A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, ...
s. ClangBSD aims to replace some GPL dependencies in the FreeBSD base system by replacing the
GNU compiler collection The GNU Compiler Collection (GCC) is an optimizing compiler produced by the GNU Project supporting various programming languages, hardware architectures and operating systems. The Free Software Foundation (FSF) distributes GCC as free softwar ...
with the BSD-licensed
LLVM LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
/ 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 Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mul ...
, 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 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 DesktopBSD is a Unix-derivative, desktop-oriented operating system based on FreeBSD. Its goal is to combine the stability of FreeBSD with the ease-of-use of K Desktop Environment 3, which is the default graphical user interface. History an ...
(desktop-oriented operating system, originally based on KDE) * TrueNAS (for network-attached storage devices) *
FreeSBIE FreeSBIE is a live CD, an operating system that is able to load directly from a bootable CD with no installation process or hard disk. It is based on the FreeBSD operating system. Its name is a pun on frisbee. Currently, FreeSBIE uses Xfce and F ...
(
live CD A live CD (also live DVD, live disc, or live operating system) is a complete bootable computer installation including operating system which runs directly from a CD-ROM or similar storage device into a computer's memory, rather than loading f ...
) *
GhostBSD GhostBSD is a Unix-like operating system based on FreeBSD, with MATE as its default desktop environment (GNOME was the previous desktop environment) and an Xfce-desktop community based edition. It aims to be easy to install, ready-to-use and ...
( MATE-based distribution, which also offers other desktop environments) *
MidnightBSD MidnightBSD is a free Unix, desktop-oriented operating system originally forked from FreeBSD 6.1, and periodically updated with code and drivers from later FreeBSD releases. Its default desktop environment, Xfce, is a lightweight user friendly ...
* NanoBSD * PicoBSD * IntelliStar (satellite system that runs TV programs such as Weatherscan and Local On The 8s) * m0n0wall (firewall) *
OpenServer 10 Xinuos OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source computer operating system developed by Santa Cruz Operation (SCO), later acquired by SCO Group, and now owned by Xinuos. Early versions of OpenServer were ...
(server) * OPNsense (firewall) * pfSense (firewall) *
TrueOS TrueOS (formerly PC-BSD or PCBSD) is a discontinued Unix-like, server-oriented operating system built upon the most recent releases of FreeBSD-CURRENT. Up to 2018 it aimed to be easy to install by using a graphical installation program, and ...
, previously known as PC-BSD (aimed at home users and workstations, but with a FreeNAS-like server version and TrueOS pico for ARM 32-bit embedded devices) *
TrustedBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular op ...
* 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
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, whi ...
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.
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 ...
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 MidnightBSD is a free Unix, desktop-oriented operating system originally forked from FreeBSD 6.1, and periodically updated with code and drivers from later FreeBSD releases. Its default desktop environment, Xfce, is a lightweight user friendly ...
is a fork of FreeBSD 6.1 borrowing heavily from
NeXTSTEP NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of propri ...
, particularly in the user interface department. Darwin, the core of
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
's
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 la ...
, includes a virtual file system and network stack derived from those of FreeBSD, and components of its
userspace A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kerne ...
are also FreeBSD-derived. Some subscription services that are directly based on FreeBSD are: *
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 use ...
processes 2 million concurrent TCP connections per server. Embedded devices and embedded device operating systems based on FreeBSD include: * Juniper's
JUNOS Junos OS (also known as Juniper Junos, Junos and JUNOS) is a FreeBSD-based network operating system used in Juniper Networks routing, switching and security devices. Versioning Junos OS was first made available on 7 July 1998, with new feature ...
router operating system. *
EMC Isilon Dell EMC Isilon is a scale out network-attached storage platform offered by Dell EMC for high-volume storage, backup and archiving of unstructured data. It provides a cluster-based storage array based on industry standard hardware, and is scalab ...
's OneFS operating system. *
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 ...
's Data ONTAP 8.x and the now-superseded ONTAP GX (only as a loader for proprietary kernel-space module). *
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 ...
's Open Connect Appliance to handle content delivery. * The
PlayStation 4 The PlayStation 4 (PS4) is a home video game console developed by Sony Interactive Entertainment. Announced as the successor to the PlayStation 3 in February 2013, it was launched on November 15, 2013, in North America, November 29, 2013 i ...
("
Orbis OS The PlayStation 4 system software is the updatable firmware and operating system of the PlayStation 4. The operating system is Orbis OS, based on FreeBSD 9. Technology System The native operating system of the PlayStation 4 is Orbis OS, which ...
") * Panasas' PanFS parallel file system * pfSense, an open-source firewall, router and security appliance operating system.


Version history


See also

*
BAPP The acronyms BAPP (or B.A.P.P.) and BAMP (or B.A.M.P.) refer to a set of open-source software programs commonly used together to run dynamic web sites or servers. This set is a solution stack, and an open source web platform. ''BAPP'' refers to: * ...
, a set of commonly used software with FreeBSD * Berkeley Software Distribution *
Comparison of BSD operating systems There are a number of Unix-like operating systems based on or descended from the Berkeley Software Distribution (BSD) series of Unix variant options. The three most notable descendants in current use are FreeBSD, OpenBSD, and NetBSD, which are all ...
* Comparison of operating system kernels *
Comparison of operating systems These tables provide a comparison of operating systems, of computer devices, as listing general and technical information for a number of widely used and currently available PC or handheld (including smartphone and tablet computer) operating sy ...
* Computer Systems Research Group *
Marshall Kirk McKusick Marshall Kirk McKusick (born January 19, 1954) is a computer scientist, known for his extensive work on BSD UNIX, from the 1980s to FreeBSD in the present day. He was president of the USENIX Association from 1990 to 1992 and again from 2002 to ...


References


Citations


Sources

* * * * * * * * * * * *


External links

*
FreeBSD
on
DistroWatch DistroWatch is a website which provides news, distribution pages hit rankings, and other general information about various Linux distributions as well as other free software/ open source Unix-like operating systems. It now contains informati ...

FreeBSD on OpenSourceFeed Gallery
{{Authority control 1993 software ARM operating systems Computing platforms IA-32 operating systems Lightweight Unix-like systems PowerPC operating systems Software using the BSD license X86-64 operating systems