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 open-source
BSD operating system, accounting for more than three-quarters of all installed simply, permissively licensed
FreeBSD has similarities with Linux
, with two major differences in scope and licensing: FreeBSD maintains a complete system, i.e. the project delivers a kernel
, device driver
utilities, and documentation
, as opposed to Linux only delivering a kernel and drivers, and relying on third-parties for system software;
and FreeBSD source code
is generally released under a permissive BSD license
, as opposed to the copyleft GPL
used by Linux.
The FreeBSD project includes a security
team overseeing all software shipped in the base distribution. A wide range of additional third-party applications
may be installed using the pkg package management system
or FreeBSD Ports
, or by compiling
Much of FreeBSD's codebase
has become an integral part of other operating systems such as Darwin
(the basis for macOS
, and tvOS
(an open-source NAS
operating system), and the system software for the PlayStation 3
and PlayStation 4
In 1974, Professor Bob Fabry
of the University of California, Berkeley
, acquired a Unix source license from AT&T
. Supported by funding from DARPA
, the Computer Systems Research Group
started to modify and improve AT&T Research Unix. They called this modified version "Berkeley Unix" or "Berkeley Software Distribution
" (BSD), implementing features such as TCP/IP
, virtual memory
, and the Berkeley Fast File System
. The BSD project was founded in 1976 by Bill Joy
. But since BSD contained code from AT&T Unix, all recipients had to get a license from AT&T first 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 Jolitz
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 and create FreeBSD so that they could keep the operating system up to date. On 19 June 1993, the name FreeBSD was chosen for the project. The first version of FreeBSD was released in November 1993.
In the early days of the project's inception, a company named Walnut Creek CDROM
, upon the suggestion of the two FreeBSD developers, agreed to release the operating system on CD-ROM
. In addition to that, the company employed Jordan Hubbard
and David Greenman, ran FreeBSD on its servers, sponsored FreeBSD conferences and published FreeBSD-related books, including ''The Complete FreeBSD'' by Greg Lehey
. By 1997, FreeBSD was Walnut Creek's "most successful product". The company later renamed itself to ''The FreeBSD Mall'' and later iXsystems
Today, FreeBSD is used by many IT companies such as IBM
, Juniper Networks
, and NetApp
to build their product.
Certain parts of Apple
's Mac OS X
operating system are based on FreeBSD.
The PlayStation 3
operating system also borrows certain components from FreeBSD,
while the PlayStation 4
operating system is derived from FreeBSD 9.
, and FlightAware
are also examples of big, successful and heavily network-oriented companies which are running FreeBSD.
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.
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
, web server
, 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
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
s such as GNOME
, and Xfce
, as well as lightweight window managers such as Openbox
, and dwmbspwm
are also available to FreeBSD.
As of FreeBSD 12, support for a modern graphics stack is available via drm-kmod. A large number of wireless adapters are supported.
Although it explicitly focuses on the x86-32
platforms, FreeBSD also supports others such as ARM
to a lesser degree.
FreeBSD's TCP/IP stack is based on the 4.2BSD
implementation of TCP/IP which greatly contributed to the widespread adoption of these protocols.
FreeBSD also supports IPv6
, and wireless networking (Wi-Fi
The IPv6 and IPSec stacks were taken from the KAME project
Prior to version 11.0, FreeBSD supported IPX
protocols, but they are considered old and have now been dropped.
As of FreeBSD 5.4, support for the Common Address Redundancy Protocol
(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.
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
is a modular framework that provides RAID
(levels 0, 1, 3 currently), full disk encryption
, 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
. 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
, 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
FreeBSD provides several security-related features including access-control list
security event auditing, extended file system attributes, mandatory access control
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
/TE implementation from SELinux
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
FreeBSD ships with three different firewall packages: IPFW
. 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 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 change was made to the binary packages, but they stated that they can't guarantee the integrity of packages that were downloaded between 19 September and 11 November.
FreeBSD has been ported to a variety of instruction set architecture
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's 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 (longer) 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 computer
s, including the BeagleBone Black
, Raspberry Pi
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.
FreeBSD has a software repository
of over 30,000 applications that are developed by third parties. Examples include: windowing system
s, web browser
s, email client
s, 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 compiled
("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
to automatically fetch the desired application's source code
, 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
in Linux distribution
s. 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.
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.
, 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 jail
s 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 KVM
whereas jails are closer to LXC containers
or Solaris Zones
. Amazon EC2
AMI instances are also supported via
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.
(without the closed-source Extension Pack
) and QEMU
are available on FreeBSD.
OS compatibility layers
Most software that runs on Linux
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 emulation
; Linux's system call
interface is implemented in the FreeBSD's kernel and hence, Linux executable images
and shared libraries
are treated the same as FreeBSD's native executable images and shared libraries.
Additionally, FreeBSD provides compatibility layer
s for several other Unix-like operating system
s, in addition to Linux, such as BSD/OS
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
kernel interfaces to allow FreeBSD to run (otherwise) Windows-only network drivers.
compatibility layer, which allows the running of many Windows applications, especially games, without a (licensed) copy of Microsoft Windows
, is available for FreeBSD.
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
is the default scheduler
in FreeBSD since version 7.1, it supports SMP
The FreeBSD kernel has also a scalable event notification interface, named kqueue
. It has been ported to other BSD-derivatives such as OpenBSD
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
information from a collection of computers (laptop
s, single-board computer
s, embedded system
s, virtual machine
s, etc.) running FreeBSD.
From version 2.0 to 8.4, FreeBSD used the sysinstall program as its main installer. It was written in C
by Jordan Hubbard
. 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".
The default FreeBSD shell is the tcsh
shell for root, and sh for regular users.
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
. In addition to BSDcon, three other annual conferences, EuroBSDCon, AsiaBSDCon and BSDCan take place in Europe
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 SVN commit access. 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.
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 backport
ed (''MFC'' or ''Merge from CURRENT'' in FreeBSD developer slang) to the ''-STABLE'' branch.
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
the largest single donation to the Foundation since its inception. In December 2016, Jan Koum donated another 500 thousand dollars. Jan Koum himself is a FreeBSD user since the late 1990s and WhatsApp uses FreeBSD on its servers.
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
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 HAL
of FreeBSD versions before 7.2.
Some of the code contributed by other projects is licensed under GPL
. All the code licensed under GPL
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
s. ClangBSD aims to replace some GPL
dependencies in the FreeBSD base system by replacing the GNU compiler collection
with the BSD-licensed LLVM
compiler. ClangBSD became self-hosting on 16 April 2010.
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
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.
There are a number of software distributions based on FreeBSD. Notable derivatives include:
(desktop-oriented operating system, originally based on KDE)
(for network-attached storage
-based distribution, which also offers other desktop environments)
(satellite system that runs TV programs such as Weatherscan and Local On The 8s)
* OpenServer 10
, 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)
(for network-attached storage
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
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
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
It does not aim to stay compatible with FreeBSD and has huge differences in the kernel and basic userland
is a fork of FreeBSD 6.1 borrowing heavily from NeXTSTEP
, particularly in the user interface department.
, the core of Apple
, 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:
router operating system.
* EMC Isilon
'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
' PanFS parallel file system
, an open-source firewall, router and security appliance operating system.
, a set of commonly used software with FreeBSD
* Berkeley Software Distribution
* Comparison of BSD operating systems
* Comparison of operating system kernels
* Comparison of operating systems
* Computer Systems Research Group
* Marshall Kirk McKusick
on DistroWatchFreeBSD on OpenSourceFeed Gallery
Category:ARM operating systems
Category:Lightweight Unix-like systems
Category:PowerPC operating systems
Category:Software using the BSD license
Category:IA-32 operating systems
Category:X86-64 operating systems