There are a number of Unix-likeoperating 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 derived from 386BSD and 4.4BSD-Lite, by various routes. Both NetBSD and FreeBSD started life in 1993, initially derived from 386BSD, but in 1994 migrated to a 4.4BSD-Lite code base. OpenBSD was forked from NetBSD in 1995. Other notable derivatives include DragonFly BSD, which was forked from FreeBSD 4.8.
Most of the current BSD operating systems are open source and available for download, free of charge, under the BSD License. They also generally use a monolithic kernel architecture, apart from DragonFly BSD which feature hybrid kernels. The various open source BSD projects generally develop the kernel and userland programs and libraries together, the source code being managed using a single central source repository.
In the past, BSD was also used as a basis for several proprietary versions of UNIX, such as Sun's SunOS, Sequent's Dynix, NeXT's NeXTSTEP, DEC's Ultrix and OSF/1 AXP (which became the now discontinued Tru64 UNIX).
Aims and philosophies
FreeBSD
FreeBSD aims to make an operating system usable for any purpose.[1] It is intended to run a wide variety of applications, be easy to use, contain cutting edge features, and be highly scalable, including for network servers with very high loads.[2] FreeBSD is free software, and the project prefers the FreeBSD license. However, they sometimes accept non-disclosure agreements (NDAs) and include a limited number of nonfree hardware abstraction layer (HAL) modules for specific device drivers in their source tree, to support the hardware of companies who do not provide purely libre drivers (such as HALs to program software-defined radios so that vendors do not share their nonfree algorithms).
To maintain a high level of quality and provide good support for "production quality commercial off-the-shelf (COTS) workstation, server, and high-end embedded systems", FreeBSD focuses on a narrow set of architectures.[3] A significant focus of development since 2000[4] has been fine-grained locking and symmetric multiprocessing (SMP) scalability. From 2007 on, most of the kernel was fine-locked and scaling improvements started to be seen.[5] Other recent work includes Common Criteria security functionality, such as mandatory access control and security event audit support.
FuryBSD – a FreeBSD-based operating system, founded after Project Trident decided to build on Void Linux instead of TrueOS. Discontinued in October 2020.[6]
GhostBSD – a FreeBSD-based operating system with OpenRC and OS packages.
CheriBSD – adapted to support CHERI-MIPS, CHERI-RISC-V, and Arm Morello ISAs.[9]
NetBSD
NetBSD aims to provide a freely redistributable operating system that professionals, hobbyists, and researchers can use in any manner they wish. The main focus is portability, through the use of clear distinctions between machine-dependent and machine-independent code. It runs on a wide variety of 32-bit and 64-bit processor architectures and hardware platforms, and is intended to interoperate well with other operating systems. NetBSD places emphasis on correct design, well-written code, stability, and efficiency, where practical, close compliance with open API and protocol standards is also aimed for. In June 2008, the NetBSD Foundation moved to a two-clause BSD license, citing changes at UCB and industry applicability.[10]NPF is a project spawned by NetBSD.
Derivatives:
OS108 – system with graphical desktop environment based on NetBSD.[11]
OpenBSD
OpenBSD is a security-focused BSD known for its developers' insistence on extensive, ongoing code auditing for security and correct functionality, a "secure by default" philosophy, good documentation, and adherence to strictly open source licensing. The system incorporates numerous security features that are absent or optional in other versions of BSD. The OpenBSD policy on openness extends to hardware documentation and drivers, since without these, there can be no trust in the correct operation of the kernel and its security, and vendor software bugs would be hard to resolve.[12]
OpenBSD emphasizes very high standards in all areas. Security policies include disabling all non-essential services and having sane initial settings; and integrated cryptography (originally made easier due to relaxed Canadian export laws relative to the United States), full public disclosure of all security flaws discovered; thoroughly auditing code for bugs and security issues; various security features, including the W^X page protection technology and heavy use of randomization to mitigate attacks. Coding approaches include an emphasis on searching for similar issues throughout the code base if any code issue is identified. Concerning software freedom, OpenBSD prefers the BSD or ISC license, with the GPL acceptable only for existing software which is impractical to replace, such as the GNU Compiler Collection. NDAs are never considered acceptable. In common with its parent, NetBSD, OpenBSD strives to run on a wide variety of hardware.[13] Where licenses conflict with OpenBSD's philosophy, the OpenBSD team has re-implemented major pieces of software from scratch, which have often become the standard used within other versions of BSD. Examples include the pfpacket filter, new privilege separation techniques used to safeguard tools such as tcpdump and tmux, much of the OpenSSH codebase, and replacing GPL licensed tools such as diff, grep and pkg-config with ISC or BSD licensed equivalents.
OpenBSD prominently notes the success of its security approach on its website home page. As of July2024[update], only two vulnerabilities have ever been found in its default install (an OpenSSH vulnerability found in 2002, and a remote network vulnerability found in 2007) in a period of almost 22 years. According to OpenBSD expert Michael W. Lucas, OpenBSD "is widely regarded as the most secure operating system available anywhere, under any licensing terms."[14]
LibertyBSD – Aimed to be a 'deblobbed' version of OpenBSD.[15] There are a number of reasons as to why blobs can be problematic, according to the project.[16] LibertyBSD began going through the process to become Free Software FoundationFSDG certified, but ultimately never was accepted.[17] LibertyBSD is no longer actively developed, and the project page directs people instead to HyperbolaBSD.[18]
Isotop,[19] a French project[20] aiming to adapt OpenBSD to desktops and laptops,[21] using xfce then dwm
DragonFly BSD
DragonFly BSD aims to be inherently easy to understand and develop for multi-processor infrastructures. The main goal of the project, forked from FreeBSD 4.8, is to radically change the kernel architecture, introducing microkernel-like message passing which will enhance scaling and reliability on symmetric multiprocessing (SMP) platforms while also being applicable to NUMA and clustered systems. The long-term goal is to provide a transparent single system image in clustered environments. DragonFly BSD originally supported both the IA-32 and x86-64 platforms, however support for IA-32 was dropped in version 4.0.[22][23] Matthew Dillon, the founder of DragonFly BSD, believes supporting fewer platforms makes it easier for a project to do a proper, ground-up symmetric multiprocessing implementation.[24]
Popularity
Bar chart showing the proportion of users of each BSD variant from a BSD usage survey from September 2005.
In September 2005, the BSD Certification Group, after advertising on a number of mailing lists, surveyed 4,330 BSD users, 3,958 of whom took the survey in English, to assess the relative popularity of the various BSD operating systems. About 77% of respondents used FreeBSD, 33% used OpenBSD, 16% used NetBSD, 2.6% used Dragonfly, and 6.6% used other (potentially non-BSD) systems. Other languages offered were Brazilian and European Portuguese, German, Italian, and Polish. Note that there was no control group or pre-screening of the survey takers. Those who checked "Other" were asked to specify that operating system.[25]
Because survey takers were permitted to select more than one answer, the percentages shown in the graph, which are out of the number survey of participants, add up to greater than 100%. If a survey taker filled in more than one choice for "other", this is still only counted as one vote for other on this chart.[25]
Another attempt to profile worldwide BSD usage is the *BSDstats Project, whose primary goal is to demonstrate to hardware vendors the penetration of BSD and viability of hardware drivers for the operating system. The project collects data monthly from any BSD system administrators willing to participate, and currently records the BSD market share of participating FreeBSD, OpenBSD, NetBSD, DragonflyBSD, Debian GNU/kFreeBSD, TrueOS, and MirBSD systems.[26]
In 2020, a new independent project was introduced to collect statistics with the goal of significantly increasing the number of observed parameters.[27][28]
DistroWatch, well known in the Linux community and often used as a rough guide to free operating system popularity, publishes page hits for each of the Linux distributions and other operating systems it covers. As of 27 March 2020, using a data span of the last six months it placed FreeBSD in 21st place with 452 hits per day, GhostBSD in 51st place with 243 hits, TrueOS in 54th place with 182 hits per day, DragonflyBSD in 75th place with 180 hits, OpenBSD in 80th place with 169 hits per day and NetBSD in 109th place with 105 hits per day.[29]
Names, logos, slogans
The names FreeBSD and OpenBSD are references to software freedom: both in cost and open source.[30] NetBSD's name is a tribute to the Internet, which brought the original developers together.[31]
The first BSD mascot was the BSD daemon, named after a common type of Unix software program, a daemon. FreeBSD still uses the image, a red cartoon daemon named Beastie, wielding a pitchfork, as its mascot today. In 2005, after a competition, a stylized version of Beastie's head designed and drawn by Anton Gural was chosen as the FreeBSD logo.[32] The FreeBSD slogan is "The Power to Serve."
The NetBSD flag, designed in 2004 by Grant Bissett, is inspired by the original NetBSD logo,[33] designed in 1994 by Shawn Mueller, portraying a number of BSD daemons raising a flag on top of a mound of computer equipment. This was based on a World War II photograph, Raising the Flag on Iwo Jima. The Board of Directors of The NetBSD Foundation believed this was too complicated, too hard to reproduce and had negative cultural ramifications and was thus not a suitable image for NetBSD in the corporate world. The new, simpler flag design replaced this.[34] The NetBSD slogan is "Of course it runs NetBSD", referring to the operating system's portability.
Originally, OpenBSD used the BSD daemon as a mascot, sometimes with an added halo as a distinguishing mark, but OpenBSD later replaced its BSD daemon with Puffy. Although Puffy is usually referred to as a pufferfish, the spikes on the cartoon images give him a closer likeness to the porcupinefish. The logo is a reference to the fish's defensive capabilities and to the Blowfish cryptography algorithm used in OpenSSH. OpenBSD also has a number of slogans including "Secure by default", which was used in the first OpenBSD song, "E-railed", and "Free, Functional & Secure",[35] and OpenBSD has released at least one original song with every release since 3.0.[36]
The DragonFly BSD logo, designed by Joe Angrisano, is a dragonfly named Fred.[37] A number of unofficial logos[38] by various authors also show the dragonfly or stylized versions of it. DragonFly BSD considers itself to be "the logical continuation of the FreeBSD 4.x series."[39] FireflyBSD has a similar logo, a firefly, showing its close relationship to DragonFly BSD. In fact, the FireflyBSD website states that proceeds from sales will go to the development of DragonFly BSD, suggesting that the two may in fact be very closely related.
PicoBSD's slogan is "For the little BSD in all of us," and its logo includes a version of FreeBSD's Beastie as a child,[40] showing its close connection to FreeBSD, and the minimal amount of code needed to run as a Live CD.
A number of BSD OSes use stylized version of their respective names for logos. This includes TrueOS, GhostBSD, DesktopBSD, ClosedBSD,[41] and MicroBSD.[42] TrueOS's slogan is "Personal computing, served up BSD style!", GhostBSD's "A simple, secure BSD served on a Desktop." DesktopBSD's "A Step Towards BSD on the Desktop." MicroBSD's slogan is "The small secure unix like OS."
MirOS's site collects a variety of BSD mascots and Tux, the Linux mascot, together, illustrating the project's aim of supporting both BSD and Linux kernels. MirOS's slogan is "a wonderful operating system for a world of peace."[43]
1 2 3 4 5 6 386BSD, BSD/OS, SunOS, and Ultrix are historic operating systems that are no longer developed. BSDeviant and ekkoBSD do not exist anymore either, although BSDeviant is still available for download (see external links). MicroBSD ended, then started again in 2003, but it does not seem that any progress has been made since then, though the website still exists.
↑ This article only refers to SunOS through version 4.x. SunOS from release 5.x forward is based on SVR4, and is most commonly referred to as Solaris.
↑ "DFWiki – DragonFly Artwork". The DragonFlyBSD Project. 2006-03-28. Archived from the original on 2005-04-10. Retrieved 2006-04-22.{{cite web}}: CS1 maint: unfit URL (link)
Milo; etal. (1998-06-22). "Mac OS X". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
Milo; etal. (1998-06-22). "Mac OS X Server". Operating System Technical Comparison. OSdata. Archived from the original on 2007-01-14. Retrieved 2006-06-02.
A monolithic kernel is an operating system architecture with the entire operating system running in kernel space. The monolithic model differs from other architectures such as the microkernel in that it alone defines a high-level virtual interface over computer hardware. A set of primitives or system calls implement all operating system services such as process management, concurrency, and memory management.
Kylin is an operating system developed by academics at the National University of Defense Technology in the People's Republic of China since 2001. It is named after the mythical beast qilin. The first versions were based on FreeBSD and were intended for use by the Chinese military and other government organizations. With version 3.0, Kylin became Linux-based, and there is a version called NeoKylin which was announced in 2010.
Portage is a package management system originally created for and used by Gentoo Linux and also by ChromeOS, Calculate, and Funtoo Linux among others. Portage is based on the concept of ports collections. Gentoo is sometimes referred to as a meta-distribution due to the extreme flexibility of Portage, which makes it operating-system-independent. The Gentoo/Alt project was concerned with using Portage to manage other operating systems, such as BSDs, macOS and Solaris. The most notable of these implementations is the Gentoo/FreeBSD project.
Light Weight Kernel Threads (LWKT) is a computer science term and from DragonFly BSD in particular. LWKTs differ from normal kernel threads in that they can preempt normal kernel threads. According to Matt Dillon, DragonFlyBSD creator:
The LWKT scheduler is responsible for actually running a thread. It uses a fixed priority scheme, but the fixed priorities are differentiating major subsystems, not user processes. For example, hardware interrupt threads have the highest priority, followed by software interrupts, kernel-only threads, then finally user threads. A user thread either runs at user-kernel priority, or a user thread runs at user priority.
DragonFly does preempt, it just does it very carefully and only under particular circumstances. An LWKT interrupt thread can preempt most other threads, for example. This mimics what FreeBSD-4.x already did with its spl/run-interrupt-in-context-of-current-process mechanism. What DragonFly does *NOT* do is allow a non-interrupt kernel thread to preempt another non-interrupt kernel thread.
The mainframe z/OS Operating system supports a similar mechanism, called SRB.
SRB's represent requests to execute a system service routine. SRB's are typically created when one address space detects an event that affects a different address space; they provide one of several mechanisms for asynchronous inter-address space communication for programs running on z/OS.
An SRB is similar to a Process Control Block (PCB), in that it identifies a unit of work to the system. Unlike a PCB, an SRB cannot "own" storage areas. In a multiprocessor environment, the SRB routine, after being scheduled, can be dispatched on another processor and can run concurrently with the scheduling program. The scheduling program can continue to do other processing in parallel with the SRB routine. Only programs running in kernel mode can create an SRB.
The Windows Operating System knows a similar light weight thread mechanism named "fibers". Fibers are scheduled by an application program. The port of the CICS Transaction Server to the Windows platform uses fibers, somewhat analogous to the use of "enclaves" under z/OS.
In UNIX, "kernel threads" have two threads, one is the core thread, one is the user thread.
The BSD Daemon, nicknamed Beastie, is the generic mascot of BSD operating systems. The BSD Daemon is named after software daemons, a class of long-running computer programs in Unix-like operating systems—which, through a play on words, takes the cartoon shape of a demon. The BSD Daemon's nickname Beastie is a slurred phonetic pronunciation of BSD. Beastie customarily carries a trident to symbolize a software daemon's forking of processes. The FreeBSD web site has noted Evi Nemeth's 1988 remarks about cultural-historical daemons in the Unix System Administration Handbook: "The ancient Greeks' concept of a 'personal daemon' was similar to the modern concept of a 'guardian angel' ... As a rule, UNIX systems seem to be infested with both daemons and demons."
Berkeley Software Design, Inc., was a software company founded in 1991 by members of the Computer Systems Research Group (CSRG), known for developing and selling BSD/OS, a commercial and partially proprietary variant of the BSD Unix operating system for PCs.
TrueOS is a discontinued Unix-like, server-oriented operating system built upon the most recent releases of FreeBSD-CURRENT.
OS-level virtualization is an operating system (OS) virtualization paradigm in which the kernel allows the existence of multiple isolated user space instances, including containers, zones, virtual private servers (OpenVZ), partitions, virtual environments (VEs), virtual kernels, and jails. Such instances may look like real computers from the point of view of programs running in them. A computer program running on an ordinary operating system can see all resources of that computer. Programs running inside a container can only see the container's contents and devices assigned to the container.
Ports collections are the sets of makefiles and patches provided by the BSD-based operating systems, FreeBSD, NetBSD, and OpenBSD, as a simple method of installing software or creating binary packages. They are usually the base of a package management system, with ports handling package creation and additional tools managing package removal, upgrade, and other tasks. In addition to the BSDs, a few Linux distributions have implemented similar infrastructure, including Gentoo's Portage, Arch's Arch Build System (ABS), CRUX's Ports and Void Linux's Templates.
In the context of free and open-source software, proprietary software only available as a binary executable is referred to as a blob or binary blob. The term usually refers to a device driver module loaded into the kernel of an open-source operating system, and is sometimes also applied to code running outside the kernel, such as system firmware images, microcode updates, or userland programs. The term blob was first used in database management systems to describe a collection of binary data stored as a single entity.
Linux 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 (distro), which includes the kernel and supporting system software and libraries—most of which are provided by third parties—to create a complete operating system, designed as a clone of Unix and released under the copyleft GPL license.
HAL is a software subsystem for UNIX-like operating systems providing hardware abstraction.
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD) which currently runs on IA-32, x86-64, ARM, PowerPC and RISC-V based computers. The first version was released in 1993 developed from 386BSD—the first fully functional and free Unix clone—and has since continuously been the most commonly used BSD-derived operating system.
The Berkeley Software Distribution (BSD), also known as Berkeley Unix or BSD Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley beginning in 1978. It began as an improved derivative of AT&T's original Unix that was developed at Bell Labs, based on the source code but over time diverging into its own code. BSD would become a pioneer in the advancement of Unix and computing.
NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems.
Lumina Desktop Environment, or simply Lumina, is a plugin-based desktop environment for Unix and Unix-like operating systems. It was designed specifically as a system interface for TrueOS and systems derived from Berkeley Software Distribution (BSD) in general, but it has been ported to various Linux distributions.
The history of the Berkeley Software Distribution began in the 1970s when University of California, Berkeley received a copy of Unix. Professors and students at the university began adding software to the operating system and released it as BSD to select universities. Since it contained proprietary Unix code, it originally had to be distributed subject to AT&T licenses. The bundled software from AT&T was then rewritten and released as free software under the BSD license. However, this resulted in a lawsuit with Unix System Laboratories, the AT&T subsidiary responsible for Unix. Eventually, in the 1990s, the final versions of BSD were publicly released without any proprietary licenses, which led to many descendants of the operating system that are still maintained today.
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