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 variants. 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 migrating to a 4.4BSD-Lite code base. OpenBSD was forked in 1995 from NetBSD. Other notable derivatives include DragonFly BSD, which was forked from FreeBSD 4.8, and Apple Inc.'s iOS and OS X, with its Darwin base including a large amount of code derived from FreeBSD.
Most of the current BSD operating systems are open source and available for download, free of charge, under the BSD License, the most notable exceptions being OS X and iOS. They also generally use a monolithic kernel architecture, apart from OS X and 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 (now Tru64 UNIX). Parts of NeXT's software became the foundation for OS X which, together with iOS, is among the most commercially successful BSD variants in the general market.
Aims and philosophies
DragonFly BSD aims to be inherently easy to understand and develop for multi-processor infrastructures. Forking from FreeBSD 4.8, the main goal of the project is to radically change the kernel architecture, introducing microkernel-like message passing which will enhance scaling and reliability on symmetric multiprocessing 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 (or AMD64) platforms, however version 4.0 dropped support for IA-32. Matthew Dillon, the founder of DragonFly BSD, believes supporting fewer platforms makes it easier for a project to do a proper, ground-up SMP implementation.
FreeBSD aims to make an operating system usable for any purpose. It is intended to run a wide variety of applications, be easy to use, contain cutting edge features, and be highly scalable on very high load network servers. FreeBSD is free and open source, and the project prefers the BSD license. However, they sometimes accept non-disclosure agreements (NDAs) and include a limited number of closed-source HAL modules for specific device drivers in their source tree, to support the hardware of companies who do not provide purely open source drivers (such as HALs to program software-defined radios so that vendors do not share their proprietary 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. A significant focus of development since 2000  has been fine-grained locking and SMP scalability. From 2007 on, most of the kernel was fine-locked and scaling improvements started to be seen. Other recent work includes Common Criteria security functionality, such as mandatory access control and security event audit support.
PC-BSD aims at user friendliness for the layperson. KDE was the default desktop environment up to PC-BSD8, but as of PC-BSD9 a range of environments including KDE, GNOME, Xfce, and LXDE, and many window managers are available to choose from during the installation. An easy to use software manager is included, which downloads and installs binary packages in PC-BSD's own .pbi format. Each version of PC-BSD remains directly descended from the same version of FreeBSD. The FreeBSD community will typically point users looking for an "easy" BSD to the PC-BSD project.
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. NPF is a project spawn by NetBSD.
OpenBSD aims at security, correctness, and being as free as possible. Security policies include revealing security flaws publicly, known as full disclosure; thoroughly auditing code for bugs and security issues; various security features, including the W^X page protection technology and heavy use of randomization; a "secure by default" philosophy including 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. 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.
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.
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.
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, PC-BSD, and MirBSD systems.
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 June 10, 2013, using a data span of the last six months it placed FreeBSD in 20th place with 529 hits per day; PC-BSD in 40th place with 295 hits per day; GhostBSD in 66th place with 193 hits, NetBSD in 78th place with 172 hits per day; OpenBSD in 82nd place with 165 hits per day; and MidnightBSD in 194th place with 38 hits per day.
Names, logos, slogans
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. The FreeBSD slogan is "The Power to Serve."
The NetBSD flag, designed in 2004 by Grant Bisset, is inspired by the original NetBSD logo, 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. 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", and OpenBSD has released at least one original song with every release since 3.0.
The DragonFly BSD logo, designed by Joe Angrisano, is a dragonfly named Fred. A number of unofficial logos 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." 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, 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 OS X, PC-BSD, GhostBSD, DesktopBSD, ClosedBSD, and MicroBSD. The OS X logo is the Roman numeral for 10. This is intended to emphasize the change from previous versions of Mac OS, which were not based on BSD and had version numbers expressed using the arabic numerals up to 9. PC-BSD'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."
|Primary developers||First public release||Based on||Latest stable version||Cost (USD)||Preferred license||Purpose||Short description|
|FreeBSD||The FreeBSD Project||1993-12-01||386BSD, 4.4BSD-Lite||10.2||2015-08-13||Free||Simplified BSD||Server, Workstation, Network Appliance, Embedded||Aims for maximum performance.|
|OpenBSD||The OpenBSD Project||1996-09-01||NetBSD 1.0||5.8||2015-10-18||Free||ISC||Server, Workstation, Network Appliance, Embedded||Aims for maximum security.|
|NetBSD||The NetBSD Project||1993-05-01||386BSD, 4.4BSD-Lite||7.0||2015-10-08||Free||Simplified BSD||Server, Workstation, Network Appliance, Embedded||Aims for maximum portability.|
|DragonFly BSD||Matt Dillon||2004-07-12||FreeBSD 4.8||4.0.3||2015-01-21||Free||Modified BSD||Server, Workstation, Network Appliance, Embedded||Aims for maximum scalability.|
|386BSD [Note 1]||William and Lynne Jolitz||1992-03-01||4.3BSD Net/2||1.0||1994-11-01||Free||BSD||Open source general purpose||Historical|
|BSD/OS (BSD/386) [Note 1]||BSDi, Wind River Systems||1993-03-01||4.3BSD Net/2, 4.4BSD||5.1||2003-10-01||?||Proprietary||General purpose||Historical|
|SunOS [Note 1][Note 2]||Sun Microsystems||1982||4.xBSD, UNIX System V||4.1.4||1994-11-01||Included in hardware and support charges||Proprietary||Server, Workstation||Historical (Solaris is a different code base)|
|Ultrix [Note 1]||Digital Equipment Corporation||1984||4.2BSD, SVR2||4.5||1995||?||Proprietary||General Purpose||Historical (ran on DEC VAX & MIPS systems or emulators).|
|Tru64 UNIX (DEC OSF/1, Digital UNIX)||DEC, Compaq, HP||1993||4.3BSD, 4.4BSD, Mach 2.5, UNIX System V||5.1B-6||2010-10-01||Non-free $99 (non-commercial)||Proprietary||General Purpose||Only runs on HP Alpha systems or emulators.|
|OS X||Apple Inc.||2001-03-24||Darwin||10.11 "El Capitan"||2015-10-30||Client: Free
Server (add-on application): $19.99
|Open source core system (see Darwin) with proprietary higher level API layers locking to Apple hardware||Workstation, Home Desktop, Server||Locked to Apple hardware use only|
|iOS||Apple Inc.||2007-06-01||Darwin||9.0.2||2015-10-30||Free||Open source core system (see Darwin) with proprietary higher level API layers locking to Apple hardware||Embedded mobile device||Ships with Apple iPhone, iPad, iPod Touch, Apple TV|
|Darwin||Apple Inc.||2001-03-01||NeXTSTEP, FreeBSD, Mac OS||15.0.0||2015-09-16||Free||APSL, GPL and others||Workstation, Home Desktop, Server||The kernel and certain userland components of OS X|
|PC-BSD||iXsystems, Inc.||2006-04-29||FreeBSD||10.2||2015-08-21||Free||BSD||Desktop||Easy to use while maintaining full use of FreeBSD base|
|GhostBSD||Eric Turgeon, Fomoro Daniel Soromou||2009-11-01||FreeBSD||10.1||2015-09-13||Free||BSD||Desktop, Workstation||Easy to use, full FreeBSD w/ GNOME, Mate, Xfce, LXDE or Openbox.|
|DesktopBSD||Peter Hofer, Daniel Seuffert||2005-07-25||FreeBSD||1.7||2009-09-07||Free||BSD||Desktop||Easy to use|
|ClosedBSD||Joshua Bergeron and various contributors||?||FreeBSD||1.0B (floppy), 1.0-RC1 (CD)||?||Free||Proprietary||?||firewall/NAT, boot floppy, Live CD|
|FreeSBIE||?||?||FreeBSD||2.0.3||2007-02-01||Free||?||?||Live CD of FreeBSD. DistroWatch lists as discontinued.|
|PicoBSD||Michael Bialecki||?||FreeBSD||0.42||?||Free||BSD||boot floppy||?|
|Anonym.OS||?||2005-01-01||OpenBSD 3.8||none (beta only)||?||Free||?||Anonymous browsing||Live CD|
|MirOS BSD||The MirOS Project||?||OpenBSD 3.1||#10||2008-03-16||Free||?||?||European|
|ekkoBSD [Note 1]||Rick Collette||?||OpenBSD 3.3||?||?||?||?||Server||easy to administer|
|MicroBSD [Note 1]||Bulgarians||?||OpenBSD 3.0/3.4||0.6||2003-10-27||Free||?||General purpose||Small, secure|
|OliveBSD||Gabriel Paderni||?||OpenBSD 3.8||?||?||Free||?||Live CD||DistroWatch lists as discontinued.|
|Gentoo/FreeBSD||Gentoo Linux developers||?||FreeBSD||?||?||Free||GPL, BSD||Server, Workstation, Network Appliance||uses Gentoo framework|
|Gentoo/OpenBSD||Gentoo Linux developers||?||OpenBSD||?||?||Free||GPL, BSD||Server, Workstation, Network Appliance, Embedded||uses Gentoo framework|
|Gentoo/NetBSD||Gentoo Linux developers||?||NetBSD||?||?||Free||GPL, BSD||Server, Workstation, Network Appliance, Embedded||uses Gentoo framework|
|Gentoo/DragonflyBSD||Robert Sebastian Gerus (project not yet officially supported by Gentoo)||?||DragonFly BSD||?||?||Free||?||Server, Workstation, Network Appliance||uses Gentoo framework|
|Debian GNU/kFreeBSD||The Debian GNU/kFreeBSD team||2011-02-06||GNU, FreeBSD||7.5||2014-04-26||Free||DFSG||General purpose||GNU userspace on FreeBSD kernel|
|Debian GNU/NetBSD||The Debian GNU/kNetBSD team||Abandoned||GNU, NetBSD||Abandoned||Abandoned||Free||DFSG||General purpose||GNU userspace on NetBSD kernel|
|MidnightBSD||Lucas Holt||2007-08-04||FreeBSD 6.1 beta||0.5||2014-09-22||Free||BSD||Desktop||GNUstep based Desktop Environment|
|pfSense||various contributors||2006-10-04||FreeBSD||2.2.4||2015-07-26||Free||BSD||Security appliance||firewall/NAT, Live CD|
|Paxym FreeBSD for Octeon||Paxym Inc.||2007-12-11||FreeBSD 7.0||4.7||2008-08-13||?||Proprietary||Network, Storage, Security Applications: Routers/UTM/Firewall/NAS||For Cavium Networks Octeon MIPS architecture multicore processors |
|MaheshaBSD ||?||FreeBSD 8||?||?||Free||BSD||FreeBSD multipurpose|
|KarmaBSD ||?||FreeBSD 8
|?||?||Free||Free software||FreeBSD, OpenBSD Firewall, MP3 player, backup, others|
|Jibbed ||OpenBSD, NetBSD||6.0||Free||BSD||Live CD of NetBSD|
|Developer||First public release||Based on||Version||Release Date||Cost (USD)||Preferred license||Purpose||Short description|
- 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 the [[Solaris (operating system)|]].
|Supported architectures||Supported file systems[Note 1]||Kernel type||GUI on by default[Note 2]||Package management||Update management||Primary APIs[Note 3]|
|FreeBSD||x86, x86-64, PC98, Itanium, UltraSPARC, ARM, MIPS, PPC, others||UFS, UFS2, ext2, FAT, ISO 9660, UDF, NFS, SMBFS, NetWare (nwfs), NTFS (limited read-write), ReiserFS (read only), XFS (experimental), ZFS, FUSE, Coda (experimental), AFS, others||Monolithic with modules||No (X.Org available)||ports tree, packages||source (svn, portsnap), network binary update (freebsd-update, pkg)||BSD, POSIX|
|OpenBSD||x86, 68k, Alpha, x86-64, SPARC, UltraSPARC, ARM, MIPS, PPC, VAX, others||UFS, UFS2, ext2, FAT, ISO 9660, UDF, NFS, NTFS (read only), AFS, FUSE, others||Monolithic[Note 4]||No (X.Org included)[Note 5]||ports tree, packages||source (CVS, CVSync, rsync) or binary upgrade||BSD, POSIX|
|NetBSD||x86, 68k, Alpha, x86-64, PPC, SPARC, UltraSPARC, ARM, others||UFS, UFS2, ext2, FAT, ISO 9660, NFS, LFS, UDF, SMBFS, Coda, HFS+ (read only), EFS (read only), NTFS (read only), TMPFS, FUSE, PUFFS (BSD replacement of FUSE), ADOS (AmigaDOS file system), filecorefs (Acorn RISC OS file system), others||Monolithic with modules||No (X.Org or XFree86 included)[Note 6]||pkgsrc, packages||source (CVS, CVSup, rsync) or binary (using sysinst)||BSD, POSIX|
|Ultrix||VAX, PDP-11, MIPS||UFS + others||Monolithic||No (X11 included)||setld||?||BSD, POSIX (4.0 onwards)|
|Tru64 UNIX||Alpha||UFS, AdvFS, ISO 9660, UDF, NFS||Hybrid||Yes (CDE)||setld||dupatch||POSIX, UNIX 98, X11, CDE, others|
|OS X / Darwin||PPC, x86, x86-64, ARM||HFS+ (default), exFAT, HFS, UFS, AFP, ISO 9660, FAT, UDF, NFS, SMBFS, NTFS (read only), FTP, WebDAV, others||Hybrid||Yes (Aqua)||OS X Installer||Software Update||Carbon, Cocoa, BSD/POSIX, CF, X11 (since 10.3)|
|DragonFly BSD||x86-64||HAMMER, UFS, FAT, ISO 9660, NFS, SMBFS, NTFS, ext2, others||Hybrid||No (X.Org available)||dports, pkgng||Git||BSD, POSIX|
|PC-BSD||x86-64||UFS, UFS2, FAT, ISO 9660, NFS, SMBFS, NTFS (read only), ZFS, others||Monolithic with modules||Yes (KDE)||graphical installation wizard, ports tree||CVSup, Portsnap, network binary update (Online Update)||BSD, POSIX, X11, KDE|
|MidnightBSD||x86, x86-64||UFS, UFS2, ext2, FAT, ISO 9660, UDF, NFS, SMBFS, NetWare (nwfs), NTFS (read only), others||Monolithic with modules||No (X.Org available)||ports tree, packages||source CVSup||BSD, POSIX, X11, GNUstep|
|GhostBSD||x86, x86-64||UFS, UFS2, ext2, FAT, ISO 9660, UDF, NFS, SMBFS, NetWare (nwfs), NTFS (limited read-write), ReiserFS (read only), XFS (experimental), ZFS, FUSE, Coda (experimental), AFS, others||Monolithic with modules||Yes (MATE)||ports tree, packages||source (CVSup, portsnap), network binary update (freebsd-update)||BSD, POSIX|
- UFS and UFS2 are descendants of the old FFS. However, many BSD operating systems refer to UFS1 as FFS.
- Operating systems where the GUI is not installed and turned on by default are often bundled with an implementation of the X Window System. However, installing X is usually optional.
- Most operating systems use proprietary APIs in addition to any supported standards.
- OpenBSD contains support for modules on some architectures. They are used only to add third-party features: extracting existing functions into modules in the same manner as FreeBSD is not possible.
- Unlike FreeBSD, OpenBSD includes the X Window System as base install sets rather than packages within the ports collection. It includes some local changes and is managed as part of the OpenBSD source tree.
- NetBSD includes either X.Org or XFree86 (depending on platform) as a base install set and includes some local changes, maintained within the NetBSD source tree.
|Resource access control||Security logging||Subsystem isolation mechanisms||Integrated firewall||Encrypted file systems||Data execution prevention|
|OS X||Unix, ACLs, MAC||syslog, CAPP event auditing, OpenBSM||chroot, sandbox||IPFW2 (deprecated), PF||Yes||Yes[Note 1]||No[Note 2]|
|FreeBSD||Unix, ACLs, MAC||syslog, CAPP event auditing, OpenBSM||chroot, jail, MAC partitions, Capsicum||IPFW2, IPFilter, PF||Yes||Yes||Yes[Note 3]|
|PC-BSD||Unix, ACLs, MAC||?||chroot, jail, MAC Partitions||IPFW2, IPFilter, PF||Yes[Note 4]||Yes||No|
|GhostBSD||Unix, ACLs, MAC||syslog, CAPP event auditing, OpenBSM||chroot, jail, MAC partitions, Capsicum||IPFW2, IPFilter, PF||Yes||Yes||Yes[Note 3]|
|MidnightBSD||Unix, ACLs, MAC||syslog||chroot, jail, MAC partitions||IPFW2, IPFilter, PF||Yes||No||No|
|DragonFly BSD||Unix||syslog||chroot, jail, VKernel||IPFW2, IPFilter, PF||Yes||No||No|
|NetBSD||Unix, Veriexec||syslog||chroot, privilege separation||IPFilter, PF, NPF||Yes||Yes||Yes|
|OpenBSD||Unix||syslog||chroot, systrace, privilege separation||PF||Yes[Note 5]||Yes||Yes|
- Stack-only protection for Mac OS X 10.4, stack and heap for Mac OS X 10.5 and above.
- CPU architectures without hardware data execution prevention are not officially supported, no emulation needed.
- ProPolice/Stack-Smashing Protector has been enabled in base system since FreeBSD 8.0-RELEASE.
- Additionally swap space may be encrypted during installation, uses memory based tmp file storage by default.
- Swap space encrypted by default on OpenBSD 3.8 and above
- List of BSD operating systems
- BSD license
- Comparison of open source operating systems
- Comparison of operating systems
Notes and references
- "DragonFly Frequently Asked Questions". The DragonFly BSD Project. Archived from the original on 2006-06-15. Retrieved 2006-07-01.
- "DragonFlyBSD: FAQ-English". The DragonFly BSD Project. Retrieved 2014-12-24.
- Biancuzzi, Federico (2004-07-08). "Behind DragonFly BSD An Interview with the developers.". O’Reilly Media, Inc. p. 3. Retrieved 2006-04-29.
- "Chapter 1 Introduction: 1.2. - What is the goal of the FreeBSD Project?". Frequently Asked Questions for FreeBSD 4.X, 5.X, and 6.X. The FreeBSD Documentation Project. 1995–2006. Retrieved 2006-04-22.
- "About FreeBSD". The FreeBSD Project. 2006-10-12. Retrieved 2006-10-14.
- "Support for Multiple Architectures: Statement of General Intent". Committer's Guide. The FreeBSD Documentation Project. ©1999-2005. Retrieved 2006-10-14.
The FreeBSD Project targets "production quality commercial off-the-shelf (COTS) workstation, server, and high-end embedded systems".Check date values in:
- "Destabilization due to SMP development". Retrieved 27 May 2015.
- Moore, Kris (March 14, 2011). "A Quick Look at the Upcoming PC-BSD 9". Official PC-BSD Blog. Retrieved November 21, 2011.
- "FreeBSD Form Post "Seriously"". FreeBSD Forums. 2011-04-14. Retrieved 2011-04-14.
- "About the NetBSD Project - What is the NetBSD project?". The NetBSD Foundation, Inc. 2006-01-08. Retrieved 2006-04-22.
- "OpenBSD Project Goals". OpenBSD. 2005-10-12. Retrieved 2006-04-22.
- BSD Certification site; PDF of usage survey results. Retrieved on 2012-09-16.
- "*BSD Usage Statistics". The *BSD Stats Project. Retrieved 2006-09-30.
- "DistroWatch.com: Put the fun back into computing.". DistroWatch.com. 2001–2011. Retrieved 2011-06-12.
- "Chapter 1 Introduction - Why is it called FreeBSD?". Frequently Asked Questions for FreeBSD 4.X, 5.X, and 6.X. The FreeBSD Documentation Project. 1995–2006. Retrieved 2006-06-11.
- "About the NetBSD Project - Why the name?". The NetBSD Foundation. 1994–2006. Retrieved 2006-12-06.
- FreeBSD Logo Competition. The FreeBSD Project. Competition ended 2005-06-30. Retrieved on 2006-04-22.
- Mueller, Shawn (1994). "Original NetBSD Logo" (JPEG). The NetBSD Foundation. Retrieved 2006-04-22. Also see NetBSD Logos.
- Mewburn, Luke (2004-01-14). "NetBSD logo design competition". Netbsd-advocacy mailing list. Retrieved 2006-04-22.
Linked to from:
"Changes and NetBSD News in 2004 - NetBSD Logo Design Contest". The NetBSD Foundation, Inc. 2004-01-13. Retrieved 2006-10-14.
"The NetBSD Foundation Press Release: Announcement of New Logo - NetBSD has a new logo!". The NetBSD Foundation, Inc. 2004-10-30. Retrieved 2006-04-22.
- "OpenBSD 3.9 - Free, Functional & Secure" (JPEG). OpenBSD. Retrieved 2006-07-01.
- "OpenBSD release song lyrics". OpenBSD. 2006-04-15. Retrieved 2006-04-22.
- official DragonFlyBSD artwork
- "DFWiki - DragonFly Artwork". The DragonFlyBSD Project. 2006-03-28. Retrieved 2006-04-22. (This page was noted to be a redirect to the front page of new DragonFly Wiki on 2006-06-17, but most of the old images remain available via the Wayback Machine.)
- "The History of DragonFly". The DragonFly BSD Project. Archived from the original on 2006-04-14. Retrieved 2006-04-22.
- "PicoBSD Banner - For the little BSD in all of us". The FreeBSD Project. Archived from the original (GIF) on 2006-05-03. Retrieved 2006-04-22.
- "ClosedBSD logo". Archived from the original (JPEG) on 2005-03-18. Retrieved 2006-10-14. Original last retrieved on 2006-04-22.
- "MicroBSD logo - The small secure unix like OS" (PNG). Retrieved 2006-04-22.
- "MirOS/MirPorts: a wonderful operating system for a world of peace". MirOS Project. Retrieved 2006-04-22.
- "SunOS 4.1.3: svidii - overview of the System V environment". FreeBSD Hypertext Man Pages. The FreeBSD Project. 1989-09-30. Retrieved 2006-06-14.
- OS X#Version 10.0: .22Cheetah.22
- "MidnightBSD News". Retrieved 27 May 2015.
- "About MidnightBSD :: MidnightBSD". Retrieved 27 May 2015.
- "Paxym - FreeBSD for OCTEON CPU". Retrieved 27 May 2015.
- "FreeBSD MaheshaBSD Project". Retrieved 27 May 2015.
- "One Floppy OpenBSD MP3 Player". Retrieved 27 May 2015.
- Milo; et al. (1998-06-22). "FreeBSD". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
- Milo; et al. (1998-06-22). "OpenBSD". Operating System Technical Comparison. Retrieved 2006-06-02.
- Milo; et al. (1998-06-22). "NetBSD". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
- Milo; et al. (1998-06-22). "SunOS". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
- "SunOS & Solaris version history". Berkeley. Archived from the original on 2006-02-09. Retrieved 2006-06-02.
- "Ultrix FAQ". 1996-11-04. Archived from the original on 2006-05-19. Retrieved 2006-06-02.
- Milo ' (1998-06-22). "Ultrix". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
- Milo; et al. (1998-06-22). "Mac OS X". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
- Milo; et al. (1998-06-22). "Mac OS X Server". Operating System Technical Comparison. OSdata. Retrieved 2006-06-02.
- "BSDeviant download page". Bsdeviant.org. Retrieved 2008-06-30. A semi-official download page.
- "ekkoBSD 1.0 BETA1B Released". Slashdot. 2003-11-25. Retrieved 2006-06-03.
- Milo; et al. (1998-05-31). "Operating System Technical Comparison". OSdata. Retrieved 2006-06-02.
- Brown, Martin (2004-08-10). "Differentiating Among BSD Distros". Jupitermedia Corporation. p. 4. Retrieved 2006-06-03.
- Schneider, Wolfram; Gilliam, Josh; Schultz, Steven M. (1997–2004). "The UNIX system family tree: Research and BSD" (ASCII). The NetBSD Foundation. Retrieved 2006-06-03.