December 21 2023

Guide to BSD and Derivatives such as FreeBSD, NetBSD and OpenBSD

Exploring the differences between BSD Open Source operating systems. An in-depth analysis of FreeBSD, NetBSD, OpenBSD and their specific applications.

Early Unix distributions from Bell Labs in the 70s included the operating system's source code, allowing university researchers to modify and extend it. Unix arrived at Berkeley in 1974, at the request of computer science professor Bob Fabry, who had been on the committee of the Symposium on Principles of Operating Systems where Unix was first introduced. A PDP-11/45 was purchased to run the system. The following year, a larger PDP-11/70 was installed in Berkeley, funded by the Ingres database project. To understand BSD you have to go far back into the history of Unix, the operating system first released by AT&T's Bell Labs in 1969. BSD began as a variant of Unix that programmers at the University of California at Berkeley, initially led by Bill Joy, began to develop in the late 70s.

Initially, BSD was not a clone of Unix, nor a substantially different version. It only included a few extra features, which were intertwined with AT&T's proprietary code.

In 1975, Ken Thompson took a sabbatical from Bell Labs and came to Berkeley as a visiting professor. He helped install Version 6 of Unix and began working on a Pascal implementation for the system. Graduate students Chuck Haley and Bill Joy improved Thompson's Pascal and implemented an improved text editor, ex. Other universities became interested in Berkeley software, so in 1977 Joy began compiling the first Berkeley Software Distribution (1BSD), which was released on March 9, 1978. 1BSD was an add-on to Unix Version 6 rather than a full operating system to itself. About thirty copies were sent.

The second Berkeley Software Distribution (2BSD), released in May 1979, included updated versions of the 1BSD software as well as two new Joy programs that persist on Unix systems to this day: the text editor vi (a visual version of ex) and the C shell. About 75 copies of 2BSD were sent by Bill Joy.

A VAX computer was installed in Berkeley in 1978, but the version of Unix for the VAX architecture, UNIX/32V, did not take advantage of the VAX's virtual memory capabilities. The 32V kernel was largely rewritten to include Berkeley graduate student Özalp Babaoğlu's virtual memory implementation, and a complete operating system including the new kernel, 2BSD tool ports for the VAX, and 32V tools was released as 3BSD in late 1979. 3BSD was also alternatively called Virtual VAX/UNIX or VMUNIX (for Virtual Memory Unix), and BSD kernel images were normally called /vmunix until 4.4BSD.

After the release of 4.3BSD in June 1986, it was decided that BSD would move away from the aging VAX platform. The Power 6/32 platform (codenamed “Tahoe”) developed by Computer Consoles Inc. seemed promising at the time, but was abandoned by its developers shortly thereafter. However, the 4.3BSD-Tahoe port (June 1988) proved invaluable, as it led to a separation of machine-dependent and machine-independent code in BSD, thus improving the system's future portability.

In addition to portability, the CSRG worked on an implementation of the OSI network protocol stack, improvements to the kernel virtual memory system, and (with LBL's Van Jacobson) new TCP/IP algorithms to accommodate the growth of the Internet.

Until then, all versions of BSD used AT&T's proprietary Unix code and were therefore subject to a software license from AT&T. Source code licenses had become very expensive, and several external parties had expressed interest in a separate release of the network code, which had been developed entirely outside of AT&T and would therefore not be subject to the licensing requirement. This led to Networking Release 1 (Net/1), which was made available to non-licensees of AT&T code and was freely redistributable under the terms of the BSD license. It was released in June 1989.

After Net/1, BSD developer Keith Bostic proposed that more non-AT&T sections of the BSD system be released under the same license as Net/1. To this end, he began a project to reimplement most of the standard Unix tools without using AT&T code. Within eighteen months, all AT&T tools were replaced, and it was determined that only a few AT&T files remained in the kernel. These files were removed, and the result was the June 1991 release of Networking Release 2 (Net/2), a nearly complete operating system that was freely distributable.

Net/2 was the basis for two separate BSD ports for the Intel 80386 architecture: William Jolitz's free 386BSD and Berkeley Software Design's (BSDi) proprietary BSD/386 (later renamed BSD/OS). 386BSD was short-lived, but became the initial code base for the NetBSD and FreeBSD projects that were started shortly thereafter.

BSD soon found itself in legal trouble with AT&T Unix subsidiary System Laboratories (USL), then the owner of the System V copyright and the Unix trademark. The USL lawsuit against BSDi was filed in 1992 and resulted in an injunction on distribution of Net/2 until the validity of USL's copyright claims to the source could be determined. The lawsuit slowed the development of BSD's free software descendants for nearly two years while their legal status was in question, and as a result systems based on the Linux kernel, which had no such legal ambiguity, gained more support. The lawsuit was settled in January 1994, largely in Berkeley's favor. Of the 18.000 files in Berkeley's distribution, only three needed to be removed and 70 modified to display USL copyright notices. An additional condition of the settlement was that USL would not file further lawsuits against users and distributors of Berkeley-owned code in the upcoming 4.4BSD release.

Berkeley's last release was 4.4BSD-Lite Release 2 in 1995, after which the CSRG was disbanded and BSD development at Berkeley ceased. Since then, several variants based directly or indirectly on 4.4BSD-Lite (such as FreeBSD, NetBSD, OpenBSD) have been maintained.

The permissive nature of the BSD license has allowed many other operating systems, both open-source and proprietary, to incorporate BSD source code. For example, Microsoft Windows used BSD code in its implementation of TCP/IP and includes recompiled versions of the BSD command-line networking tools from Windows 2000. Darwin, the basis for Apple's macOS and iOS, is based on 4.4 BSD-Lite2 and FreeBSD. Various commercial Unix operating systems, such as Solaris, also incorporate BSD code.

The legal dispute proved crucial to BSD's future. During this period, the BSD community worked intensively to produce a version of the operating system completely free of any AT&T proprietary code. This effort culminated in the creation of a BSD distribution that could be legally distributed and used without the restrictions imposed by the UNIX license. This event marked a fundamental turning point for BSD and for the world of operating systems in general. The “clean” version of BSD paved the way for new distributions and adaptations, allowing BSD to evolve in different directions and influence other UNIX-like operating systems, including Linux.

Going deeper into BSD

Berkeley Software Distribution, commonly known as BSD, is an operating system that has earned a solid reputation for its stability, security, and efficiency. This reputation comes not only from its long history in the operating systems landscape, but also from its constant approach to innovation and quality. BSD offers a work environment that stands out for its richness of functionality, satisfying both the needs of expert users and those of beginners in the field of computing.

One of the defining features of BSD is its wide range of applications and development tools. This operating system provides a complete suite of utilities and programs that allow users to customize and optimize their work environment according to their needs. From basic applications for word processing and web browsing, to advanced tools for programming and network management, BSD is equipped to tackle a variety of computing tasks.

Another strength of BSD is its package management system, which makes it easy to install, update, and maintain software. This system allows users to easily manage applications and dependencies, ensuring that the software is always up to date and secure. Package management in BSD is known for being intuitive and flexible, allowing users to customize their system based on their preferences and needs.

Perhaps the most unique aspect of BSD lies in its kernel architecture. Unlike other UNIX-like operating systems, such as Linux, BSD takes a monolithic, integrated approach to its kernel. This means that the BSD kernel is designed as one large program, where all essential components are tightly interconnected and optimized to work together efficiently. This architecture offers numerous benefits, including increased stability and performance, as all kernel components are developed and tested as a single cohesive system.

Differences between BSD and Linux

In the operating system landscape, BSD and Linux represent two distinct philosophies and approaches to the idea of ​​a UNIX-inspired operating system. BSD, an acronym for Berkeley Software Distribution, is a family of certified UNIX operating systems, born from the University of California at Berkeley. Linux, on the other hand, is a Unix-like operating system, created by Linus Torvalds and developed by a global community of programmers. While both share common roots in UNIX and are similar in many aspects, there are significant differences in their architectures, licensing, development philosophies, and uses.

Historically, BSD is a direct descendant of UNIX. Its origins date back to the 70s and 80s, when researchers at the University of California at Berkeley began developing their version of UNIX. This development led to the creation of a complete operating system, which includes both the kernel and a set of userland tools. BSD has been recognized as a certified UNIX operating system, meaning that it complies with the Single UNIX Specification. This allowed BSD to maintain close consistency and compatibility with UNIX standards.

Linux, on the other hand, was born in the early 90s as an independent kernel, inspired by UNIX but not directly derived from it. Linux, combined with the GNU operating system (GNU/Linux), offers a completely open source alternative to UNIX. Unlike BSD, Linux is not a certified UNIX operating system, but is considered Unix-like, meaning it emulates the UNIX environment but does not necessarily follow all of its specifications. Linux has spread rapidly thanks to its open license, the GNU General Public License (GPL), which requires that any modifications or derivations of the source code also be available under the same license.

In terms of architecture and design, BSD and Linux have some differences. BSD tends to be more conservative in its approach to software development, favoring code stability and maturity over experimental new features. This is reflected in its system architecture, which tends to be more integrated and uniform. The BSD kernel, its userland tools, and package management system are developed and maintained as a single, cohesive project. This approach offers greater consistency and facilitates optimization of the system as a whole.

In contrast, Linux follows a more modular and decentralized development model. The Linux kernel is developed independently of many of the userland tools, which are provided by separate projects such as the GNU project. This approach has its advantages, such as flexibility and speed in incorporating new technologies and ideas. However, it can also lead to greater variety between different Linux distributions, each of which can choose different combinations of kernel, GUI, userland tools, and package management systems.

Another important difference between BSD and Linux lies in their licenses. BSD uses the BSD License, a permissive license that allows users and producers to use, modify and distribute code, even in proprietary products, without obligation to release the changes to the public. In contrast, the Linux GPL requires that all changes made to the source code be made available under the same license, promoting a more open and collaborative development environment.

In conclusion, although BSD and Linux share many similarities as UNIX-inspired operating systems, they differ significantly in terms of history, architecture, development philosophy, and licensing. These differences influence not only how these systems are developed and maintained, but also how they are used in business, academic, and personal environments. The choice between BSD and Linux largely depends on the specific needs, personal preferences and development philosophy of those who use them.

Technological advancement and evolutions

Berkeley Sockets

Berkeley Unix was the first Unix to include support libraries for Internet protocol stacks: Berkeley sockets. A Unix implementation of IP's predecessor, the ARPAnet NCP, with FTP and Telnet clients, had been produced at the University of Illinois in 1975 and was available at Berkeley. However, the shortage of memory on the PDP-11s imposed complicated design and performance issues.

By integrating sockets with the Unix operating system's file descriptors, it became almost as easy to read and write data across a network as it was to access a disk. The AT&T Lab eventually released its own STREAMS library, which incorporated many of the same features into a software stack with a different architecture, but the wide distribution of the existing sockets library reduced the impact of the new API. Early versions of BSD were used to form Sun Microsystems' SunOS, founding the first wave of popular Unix workstations.

Berkeley sockets represented a significant turning point in the development of networking software. Before their introduction, network programming required the use of complex and often non-portable API interfaces. Sockets provided a simple and uniform interface for network programming, facilitating the development of applications that could communicate across different networks. This unified approach to network programming allowed greater portability of software between different Unix platforms and played a fundamental role in the spread of the Internet.

The choice to integrate sockets with Unix file descriptors was particularly innovative, since it allowed developers to use the same I/O functions used for files to operate on network connections. This meant that functions like read(), write(), and close() could be used for both disk files and network data streams, greatly simplifying network programming.

Berkeley's approach to sockets profoundly influenced the design of subsequent network interfaces, and their use became a de facto standard in network programming, especially in Unix and Linux environments. Their simplicity and power contributed to making Unix a favorite platform for the development of network software and for the creation of the first Internet servers.

Binary Compatibility

Some BSD operating systems can run native software from several other operating systems on the same architecture, using a binary compatibility layer. This is much simpler and faster than emulation; for example, it allows you to run applications intended for Linux at practically full speed. This makes BSDs not only suitable for server environments, but also for workstation environments, given the increasing availability of commercial or closed-source software exclusively for Linux. This also allows administrators to migrate legacy commercial applications, which may have only been supported by commercial Unix variants, to a more modern operating system, maintaining the functionality of those applications until they can be replaced by a better alternative.


Current variants of the operating system BSD supports many of the common IEEE, ANSI, ISO, and POSIX standards, maintaining most of the traditional BSD behavior. Like AT&T's Unix, the BSD kernel is monolithic, meaning that device drivers in the kernel run in privileged mode, as part of the core operating system.

This binary compatibility capability in BSD operating systems represents a significant advantage in terms of flexibility and convenience. For developers and system administrators, it means the ability to leverage a wide range of existing software without the need for rewriting or adaptation. This is particularly useful in environments where operational continuity and compatibility with legacy software are crucial.

Additionally, binary compatibility allows BSD systems to serve as a bridge between different software ecosystems, offering a solution for running software in mixed environments. This feature is particularly valuable in development and testing environments, where the ability to run native software for multiple operating systems on a single BSD platform can save time and resources.

BSD operating systems' adherence to common IEEE, ANSI, ISO, and POSIX standards ensures that these systems remain compatible and interoperable with other technologies and platforms. While maintaining traditional BSD features, these variants are capable of supporting modern development environments and applications, making BSD systems a versatile choice for both legacy applications and new projects. The monolithic nature of their kernel provides optimized performance and effective device driver management, which is critical in critical production environments.




FreeBSD is an advanced operating system derived from the Berkeley Software Distribution (BSD), whose development began at the University of California at Berkeley. Its first version dates back to 1993, marking an important step forward in the history of open source operating systems. FreeBSD is known for its robustness, efficiency and excellent performance, especially in server and networking.

This operating system stands out for a feature-rich environment, supporting a wide range of hardware architectures, from ARM to the classic x86-64. Its features include an advanced file system, native virtualization, and extensive security support, making it an ideal choice for enterprise applications and network infrastructures. FreeBSD is also known for its package management system, Ports, which allows users to install and manage software efficiently.

One of the main advantages of FreeBSD is its active and dedicated community of developers and users, who constantly contribute to improving and updating the operating system. FreeBSD documentation is extensive and well-curated, offering a valuable resource for users and developers. Additionally, its permissive BSD license allows for broad use and distribution of the operating system, both in open source environments and commercial applications.

For further information, insights and downloads, you can visit the official FreeBSD website at Here, users can find resources, updated documentation, and all the latest operating system releases, as well as a support community ready to assist with any FreeBSD-related questions or needs. In summary, FreeBSD presents itself as a solid and reliable choice for those looking for a versatile, powerful and well-supported operating system.



NetBSD, an integral part of the universe of operating systems derived from the Berkeley Software Distribution (BSD), is a project that began its journey in 1993. This operating system quickly distinguished itself within the open source community thanks to its commitment to extreme portability, stability and efficiency. Its ability to operate on an extraordinary variety of hardware platforms, ranging from modern workstations to embedded devices and legacy systems, makes it one of a kind.

NetBSD's design philosophy places significant emphasis on code cleanliness and modularity. This approach not only ensures greater portability but also helps keep the operating system secure and stable. The care taken in the design and development of NetBSD is reflected in its robustness, making it a reliable choice for critical applications where stability is a priority.

Another notable aspect of NetBSD is its package management system, pkgsrc. This framework provides a flexible and powerful method to install and manage software on a variety of operating systems, not limited to just NetBSD but extending to other UNIX-likes. Pkgsrc emphasizes consistency and portability, allowing users to have a consistent experience regardless of the hardware platform used.

NetBSD is also known for its community of developers and users, an active and passionate group that continually contributes to the evolution of the operating system. This community offers support, develops new features and ensures that the system remains updated with the latest technological innovations. NetBSD's permissive and flexible BSD license encourages use and distribution in both open source and commercial applications, further broadening its impact and reach.

To explore NetBSD more thoroughly, you can visit the official website at This portal is a valuable resource for anyone interested in the operating system, offering access to in-depth documentation, installation guides, the latest versions of the operating system, and a meeting point for the community.  NetBSD represents a solid choice for users looking for a UNIX-like operating system that combines portability, efficiency, and a strong focus on quality and versatility.


openbsd logo

OpenBSD, a distinctive member of the Berkeley Software Distribution (BSD) family of operating systems, began its journey into the world of operating systems in 1996. Since its inception, it has stood out for its commitment to security, code quality, and in innovation. This open source operating system is known to be one of the most secure and reliable available, making it the preferred choice in environments where safety is of the highest priority.

Security is the fundamental pillar on which OpenBSD builds all its features. The system is designed with a “security by default” mentality, which means that the default settings are geared towards ensuring maximum security. This approach is evident in many of its features, such as the use of advanced encryption tools, stringent security policies, and frequent code review to identify and fix vulnerabilities.

OpenBSD is also known for its contributions to the field of cryptography and network security. The project introduced numerous innovations, such as the PF packet filtering system and the implementation of secure network protocols such as OpenSSH and OpenBGPD. These innovations have had a significant impact not only within the OpenBSD community but also in the software world in general.

The operating system also stands out for its architectural cleanliness and attention to the correctness of the code. This is reflected in its stability and performance, making OpenBSD an ideal solution for networking, firewall, and systems applications that require a high level of integrity and security.

The OpenBSD community is made up of dedicated developers and users, who work tirelessly to maintain and improve the system. The permissive license, similar to that of other BSD systems, allows wide use in both open source projects and commercial contexts.

For more information on OpenBSD, you can visit the official website at Here, users will find detailed documentation, installation guides, the latest operating system releases, and a community support platform. In conclusion, OpenBSD establishes itself as an excellent choice for those looking for an operating system that puts security first, without compromising quality and efficiency.


In conclusion, when it comes to choosing between FreeBSD, NetBSD, and OpenBSD, it is crucial to consider the specific benefits and ideal use cases of each of these BSD operating systems. Each of these has unique characteristics that make it particularly suitable for certain applications and environments.

FreeBSD stands out for its robustness, efficiency and excellent performance, especially in the server and networking fields. It is an ideal operating system for those looking for a stable and reliable platform for business applications, network infrastructure and Dedicated Servers. Its wide range of supported applications, excellent package management, and detailed documentation also make it a solid choice for advanced desktop users. FreeBSD is therefore the right choice for those who need a versatile system, capable of handling heavy workloads and ensuring stability and security at the same time.

NetBSD, with its extreme portability, is the ideal option for projects that require a high level of operating system adaptability across different hardware platforms. From small embedded devices to large systems, NetBSD can run effectively on an incredible variety of architectures, making it perfect for research, development projects, and embedded applications. Its clean design philosophy and attention to code correctness make it a reliable and versatile solution for a wide spectrum of uses.

OpenBSD establishes itself as a leader in the field of cybersecurity. With its emphasis on security, encryption and proactive protection features, it is the operating system of choice for environments where data and network security are of the highest priority. From firewall applications to secure networking systems, OpenBSD is the best choice for those who don't want to compromise on security.

In summary, the choice between FreeBSD, NetBSD and OpenBSD should be guided by specific technical needs and project requirements. Each system offers unique strengths, and understanding these can help determine which BSD is best suited for a given environment or application. With their solid background, active community, and ongoing development commitment, all three BSD systems remain excellent choices in the open source operating system landscape.

Do you have doubts? Don't know where to start? Contact us!

We have all the answers to your questions to help you make the right choice.

Chat with us

Chat directly with our presales support.


Contact us by phone during office hours 9:30 - 19:30

Contact us online

Open a request directly in the contact area.


Managed Server Srl is a leading Italian player in providing advanced GNU/Linux system solutions oriented towards high performance. With a low-cost and predictable subscription model, we ensure that our customers have access to advanced technologies in hosting, dedicated servers and cloud services. In addition to this, we offer systems consultancy on Linux systems and specialized maintenance in DBMS, IT Security, Cloud and much more. We stand out for our expertise in hosting leading Open Source CMS such as WordPress, WooCommerce, Drupal, Prestashop, Joomla, OpenCart and Magento, supported by a high-level support and consultancy service suitable for Public Administration, SMEs and any size.

Red Hat, Inc. owns the rights to Red Hat®, RHEL®, RedHat Linux®, and CentOS®; AlmaLinux™ is a trademark of AlmaLinux OS Foundation; Rocky Linux® is a registered trademark of the Rocky Linux Foundation; SUSE® is a registered trademark of SUSE LLC; Canonical Ltd. owns the rights to Ubuntu®; Software in the Public Interest, Inc. holds the rights to Debian®; Linus Torvalds holds the rights to Linux®; FreeBSD® is a registered trademark of The FreeBSD Foundation; NetBSD® is a registered trademark of The NetBSD Foundation; OpenBSD® is a registered trademark of Theo de Raadt. Oracle Corporation owns the rights to Oracle®, MySQL®, and MyRocks®; Percona® is a registered trademark of Percona LLC; MariaDB® is a registered trademark of MariaDB Corporation Ab; REDIS® is a registered trademark of Redis Labs Ltd. F5 Networks, Inc. owns the rights to NGINX® and NGINX Plus®; Varnish® is a registered trademark of Varnish Software AB. Adobe Inc. holds the rights to Magento®; PrestaShop® is a registered trademark of PrestaShop SA; OpenCart® is a registered trademark of OpenCart Limited. Automattic Inc. owns the rights to WordPress®, WooCommerce®, and JetPack®; Open Source Matters, Inc. owns the rights to Joomla®; Dries Buytaert holds the rights to Drupal®. Amazon Web Services, Inc. holds the rights to AWS®; Google LLC holds the rights to Google Cloud™ and Chrome™; Microsoft Corporation holds the rights to Microsoft®, Azure®, and Internet Explorer®; Mozilla Foundation owns the rights to Firefox®. Apache® is a registered trademark of The Apache Software Foundation; PHP® is a registered trademark of the PHP Group. CloudFlare® is a registered trademark of Cloudflare, Inc.; NETSCOUT® is a registered trademark of NETSCOUT Systems Inc.; ElasticSearch®, LogStash®, and Kibana® are registered trademarks of Elastic NV Hetzner Online GmbH owns the rights to Hetzner®; OVHcloud is a registered trademark of OVH Groupe SAS; cPanel®, LLC owns the rights to cPanel®; Plesk® is a registered trademark of Plesk International GmbH; Facebook, Inc. owns the rights to Facebook®. This site is not affiliated, sponsored or otherwise associated with any of the entities mentioned above and does not represent any of these entities in any way. All rights to the brands and product names mentioned are the property of their respective copyright holders. Any other trademarks mentioned belong to their registrants. MANAGED SERVER® is a trademark registered at European level by MANAGED SERVER SRL, Via Enzo Ferrari, 9, 62012 Civitanova Marche (MC), Italy.

Back to top