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

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.

Standard

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

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 its feature-rich environment, supporting a wide range of hardware architectures, from ARM to 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 strengths that distinguishes FreeBSD from other BSD systems is the native and active support for the ZFS file system, thanks to the integration of OpenZFS. This makes it the only one of the most popular BSD systems to offer this functionality in a complete way. ZFS is an advanced file system and volume manager, originally designed by Sun Microsystems, that provides an incredible combination of ease of management, robustness, and performance.

Advantages of ZFS and OpenZFS

ZFS and its open-source implementation OpenZFS offer unique features:

• End-to-end data protection: Using checksum verification, ZFS automatically detects and corrects any silent data errors.
• Snapshots and Cloning: Allows you to create immutable snapshots and writable clones, useful for backups and testing of complex environments.
• Compression and Deduplication: Reduces disk space consumption and improves overall efficiency.
• Extreme scalability: Designed to easily handle hundreds of gigabytes to several petabytes of data without any performance loss.
• Pooled Storage: Combines file system management with volume management, simplifying administration.

Thanks to these features, FreeBSD with OpenZFS is an ideal choice for environments mission-critical, such as data centers, large-scale storage, cloud computing, and applications that require maximum reliability in managing large volumes of data. The ease of use of ZFS, combined with the stability and performance of FreeBSD, allows for a robust and secure operating system capable of meeting the most demanding needs.

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

For further information, insights and downloads, you can visit the official FreeBSD website at www.freebsd.org. Here, users can find resources, up-to-date documentation, and all the latest releases of the operating system, as well as a support community ready to assist with any questions or needs related to FreeBSD. In summary, FreeBSD, with OpenZFS integration, presents itself as a solid and reliable choice for those looking for a versatile, powerful, and well-supported operating system with the ability to handle mission-critical workloads and large-scale data.

NetBSD

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. The ability to operate on an extraordinary variety of hardware platforms, ranging from modern workstations, embedded devices, routers and network appliances, to legacy systems, makes it unique in its kind and incredibly versatile.

The NetBSD design philosophy places significant emphasis on code cleanliness, modularity, and structural simplicity. This approach not only ensures greater portability but also facilitates deployment on resource-constrained platforms and helps keep the operating system secure and stable. The care taken in developing and designing NetBSD results in a robust and reliable operating system, particularly suited to mission-critical environments and technical applications where stability and control are essential.

A distinctive feature of NetBSD is its support for rare and unusual hardware architectures, which is why it is often used in research, development and testing projects for specialized devices. This makes NetBSD a strategic choice in educational, emulation or older hardware recovery contexts. Its portability-oriented architecture is ideal for developers and integrators looking to maximize the adaptability of their software.

Pkgsrc: A Powerful Package Management System

A key aspect of NetBSD is its package management system, pkgsrc. This framework, in addition to providing thousands of optimized software packages, is designed to be cross-platform, running not only on NetBSD, but also on other UNIX-like systems such as macOS, Solaris, and even some Linux distributions. Pkgsrc emphasizes:

• Flexibility: Allows users to customize package installation to suit their needs.
• Coherence: Maintains a consistent experience across platforms.
• Portability: It is used on a wide range of hardware architectures, making it easy to access the latest software on very different systems.

An active and innovative community

NetBSD has a highly engaged community of developers and users. This group regularly contributes new features, improvements, and ongoing support to keep the operating system up to date with the latest technological advances. The community also ensures that documentation is clear and complete, making NetBSD accessible to new users as well.

The permissive license BSD is another strength, as it encourages the adoption of NetBSD in both open source projects and commercial applications. This flexibility has facilitated its integration into many industrial, educational and research environments.

NetBSD Applications

Due to its robustness and portability, NetBSD is used in numerous fields, including:

• Embedded systems: Routers, firewalls and IoT devices.
• Server & Hosting: Reliable and scalable solutions in the enterprise environment.
• Research and development: Support for experimental hardware and unique platforms.
• Recovering and reusing legacy hardware: To give new life to dated devices.

Resources and insights

To explore NetBSD more thoroughly, you can visit the official website at www.netbsd.org. This portal is a valuable resource for anyone interested in the operating system, offering:

• In-depth documentation.
• Installation and advanced usage guides.
• Access to the latest versions of the operating system.
• Forums and mailing lists to connect with the community.

In summary, NetBSD is an excellent choice for those looking for a UNIX-like operating system that combines portability, efficiency, stability, and a focus on code quality. Its versatility makes it an ideal platform for innovative applications and projects that require a combination of flexibility and reliability.

OpenBSD

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, OpenBSD has been characterized by an uncompromising commitment to security, code quality, and technological innovation. This open source operating system is widely recognized as one of the most secure and reliable in the world, making it a favorite choice in environments where computer security is a top priority.

Security by Default

Security is the fundamental pillar on which OpenBSD is based. The system adopts a philosophy of “security by default”, which means that the default configurations are designed to ensure the highest level of protection, while minimizing the risk of vulnerabilities. This philosophy translates into:

• Continuous code audit: Every line of code is subjected to frequent reviews to find and fix any flaws.
• Advanced prevention mechanisms: Techniques such as ProPolice for stack protection and ASLR (Address Space Layout Randomization) for memory address randomization.
• Minimizing exposure: Services are disabled by default and must be explicitly configured by the administrator.
• Critical issues in the tracks: OpenBSD includes multiple tools and protocols that integrate advanced cryptography and rigorous security policies.

Innovations in the field of security

OpenBSD is known for introducing fundamental innovations in network security and cryptography. Among its most significant contributions are:

1. OpenSSH
   A de facto standard for secure communication via the SSH protocol, used worldwide for remote server administration.
2. PF (Packet Filter)
   An extremely powerful and flexible packet filtering system used to configure firewalls and manage your network with precision.
3. OpenBGPD e OpenNTPD
   Secure, modular implementations of the BGP and NTP protocols, designed to operate with low overhead and a high degree of security.
4. FreeSSL
   A secure and clean fork of OpenSSL, designed to eliminate historical vulnerabilities and improve the security of applications that use cryptography.

Code quality and robustness

The OpenBSD design philosophy favors the architectural cleanliness , code correctness. This focus allows the system to achieve extraordinary levels of stability, making it particularly suitable for:

• Network firewalls and security gateways.
• Auditing and monitoring systems.
• Critical environments requiring high integrity and reliability.

Each OpenBSD release is thoroughly tested and maintains a regular update cycle, with the goal of continually improving the system without compromising its security.

Community and permissive license

OpenBSD is supported by a community of committed and passionate developers and users. This community actively contributes to the project, ensuring that the operating system remains at the forefront of security and performance. OpenBSD's permissive BSD license facilitates the integration of the software into open source and commercial projects, encouraging adoption and innovation.

Resources and documentation

To explore and use OpenBSD, the official website www.openbsd.org represents a fundamental resource. Here you can access:

• Complete documentation and installation guides.
• The latest versions of the operating system.
• Support tools for users and administrators.

OpenBSD is an excellent choice for those who need an operating system that puts security first without sacrificing quality and efficiency. With its focus on data protection, stability, and innovation, OpenBSD stands out as a reliable platform for mission-critical environments and for those seeking a robust, cutting-edge solution for cybersecurity.

Conclusion

In conclusion, choosing between FreeBSD, NetBSD and OpenBSD means carefully evaluating the strengths and distinctive features of each, identifying the operating system best suited to specific needs and application contexts.

FreeBSD excels in its robustness, efficiency and high performance, making it an ideal platform for enterprise servers, network infrastructure and mission-critical applications. With native support for OpenZFS, FreeBSD offers an advanced file system that combines ease of management, security and scalability, making it particularly suitable for managing environments with demanding workloads and large-scale data volumes. Its detailed documentation, advanced package management via Ports and support for a wide range of architectures also make it a prime choice for advanced desktop users and developers. FreeBSD is, therefore, the optimal choice for those looking for a versatile, reliable and performance-oriented system.

NetBSD stands out for its exceptional portability and adaptability. This operating system is a favorite for projects that require running on a wide range of hardware platforms, from the smallest embedded device to legacy systems and unique architectures. NetBSD's design philosophy, focused on modularity and code cleanliness, ensures stability and efficiency that make it perfect for research and development environments, as well as industrial or educational applications. Its flexibility makes it a powerful solution for those looking for an operating system that can be customized and run anywhere.

OpenBSD, with its uncompromising commitment to security, has established itself as the leading choice for environments where data and network protection are a top priority. Its “security by default” approach, combined with innovations such as OpenSSH, PF, and LibreSSL, makes it indispensable for firewalls, auditing systems, network gateways, and applications that require the utmost reliability. OpenBSD not only excels at proactive protection, but also ensures stability and code cleanliness that make it a reference operating system for sensitive and mission-critical projects.

In summary, the choice between FreeBSD, NetBSD and OpenBSD depends on the technical needs and specific requirements of the project:

• FreeBSD It is ideal for performance, scalability, and advanced storage and networking infrastructures.
• NetBSD It is the perfect solution for projects that require extreme portability and hardware flexibility.
• OpenBSD establishes itself as the gold standard for data security and protection.

With active communities, ongoing development efforts, and a legacy deep in the history of operating systems, these three members of the BSD family remain pillars of the open source landscape, providing robust, quality solutions for a wide range of applications.