Demystifying Linux, Unix, BSD, and the Open Source Ecosystem

What is the relationship between Linux, Unix, and BSD?

Linux, Unix, and BSD (Berkeley Software Distribution) are all operating systems, but they have different origins and development paths. Unix was developed first, by Ken Thompson, Dennis Ritchie, and others at Bell Labs in the early 1970s. Unix and its various versions were proprietary, and the source code was not freely available.

BSD is a type of Unix-like operating system based on Research Unix. It's known for its robustness and performance efficiency. BSD has several variants like FreeBSD, OpenBSD, and NetBSD, which are complete operating systems in their own right.

Linux, created by Linus Torvalds in 1991, is a clone of Unix, created from scratch. It's an open-source operating system that adheres to the principles of the Free Software Foundation, advocating for the freedom to use, study, distribute, and modify software.

Why was Linux created when Unix was already existing?

The creation of Linux was driven by the desire to have a freely available and fully open-source operating system. At the time, Unix and its various versions were proprietary, and the source code was not freely available. Linux's open-source nature has allowed developers from around the world to contribute to its development, making it incredibly versatile and adaptable. It can be found in everything from servers, to desktops, to smartphones, routers, and even household appliances.

Why was Linux built from scratch instead of cloning from BSD?

The development of Linux was largely a result of the personal interest and drive of its creator, Linus Torvalds. While BSD (Berkeley Software Distribution) is indeed a Unix-like system that was already available at the time, it was not freely distributable. When Torvalds began his project, BSD was entangled in legal issues with AT&T's Unix System Laboratories, which limited its availability.

Torvalds wanted to create an operating system that was freely available and open to modification by its users, so he decided to develop his own system that would not be encumbered by the legal issues that BSD was facing at that time. His goal was not to create a full-fledged operating system at first, but his project quickly grew and attracted the attention of other developers. As more people began to contribute, it evolved into the robust, widely-used operating system that Linux is today.

Wasn't there any copyright problem in replicating the Unix system in a different name called Linux?

While Linux is often associated with Unix due to its Unix-like nature, Linux was not a direct copy of Unix. Instead, it was a reimplementation of the Unix operating system. Linus Torvalds, the creator of Linux, used the POSIX standard (a set of standards defined for Unix-like operating systems) to guide its development. Therefore, Linux was not a copyright violation because it was a completely new creation that just happened to be very similar in design to Unix.

Why was BSD allowed to use Unix but Linux was not allowed to use BSD?

BSD (Berkeley Software Distribution) is derived from the Unix operating system. The original Unix was developed at Bell Labs (owned by AT&T) and was proprietary software. However, the University of California, Berkeley, where BSD was developed, had a license to use and develop Unix. Over time, they replaced all the original Unix code with their own, which allowed them to release the software under an open-source license (the BSD license). That's why BSD is considered a derivative of Unix.

Linux, on the other hand, was created from scratch by Linus Torvalds and other contributors. It was not based on the Unix source code, although it was heavily influenced by Unix's design principles. Linux is released under the GNU General Public License (GPL), which is a different open source license than the BSD license.

Linux has incorporated code from BSD over the years, and vice versa. The different licenses (GPL and BSD) have some compatibility, which allows for this kind of code sharing. However, it's important to note that while the BSD license allows for code to be reused in proprietary software, the GPL requires that any derivative works also be open source.

What is POSIX?

POSIX, or Portable Operating System Interface, is a family of standards specified by the IEEE for maintaining compatibility between operating systems. POSIX defines the application programming interface (API), along with command-line shells and utility interfaces, for software compatibility with variants of Unix and other operating systems.

In conclusion, the world of operating systems is rich and diverse, with a history marked by a mix of collaboration, competition, innovation, and legal challenges. Understanding the distinctions and connections between different systems like Linux, Unix, and BSD can help users and developers navigate this complex landscape.

Summary of Events:

1. 1970s: Unix is developed at Bell Labs.

2. Late 1970s-1980s: BSD, a Unix-like operating system, is developed at the University of California, Berkeley.

3. 1983: Richard Stallman starts the GNU Project with the aim of creating a free Unix-like operating system.

4. 1991: Linus Torvalds releases the Linux kernel. When combined with the GNU system, this results in a completely free Unix-like operating system.

5. Early 1990s: BSD becomes freely distributable after legal issues with AT&T's Unix System Laboratories are resolved, leading to the creation of open-source BSD variants like FreeBSD, OpenBSD, and NetBSD.

Family Tree Analogy:

Think of Unix as the grandparent in this family. Unix has several children, one of which is BSD.

BSD, after growing up and going through some legal battles, has several children of its own: FreeBSD, OpenBSD, and NetBSD.

On the other side of the family, Unix inspired the creation of the GNU system, which can be seen as another child of Unix.

However, the GNU system was missing a vital organ: a kernel. This is where Linus Torvalds steps in and creates the Linux kernel. When combined with the GNU system, this creates the GNU/Linux operating system. So, you might say that GNU/Linux is a child of both the GNU system and the Linux kernel.

In this analogy, all the members of this family share a common lineage (they are all Unix-like), but they each have their own distinct characteristics and life stories.