Episode Details

We cover an interview about Unix Architecture Evolution, another vBSDcon trip report, how to teach an old Unix about backspace, new NUMA support coming to FreeBSD, and stack pointer checking in OpenBSD.

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Unix Architecture Evolution from the 1970 PDP-7 to the 2017 FreeBSD

• Q: Could you briefly introduce yourself?

I’m a professor of software engineering, a programmer at heart, and a technology author. Currently I’m also the editor in chief of the IEEE Software magazine. I recently published the book Effective Debugging, where I detail 66 ways to debug software and systems.

• Q: What will your talk be about, exactly?

I will describe how the architecture of the Unix operating system evolved over the past half century, starting from an unnamed system written in PDP-7 assembly language and ending with a modern FreeBSD system. My talk is based, first, on a GitHub repository where I tried to record the system’s history from 1970 until today and, second, on the evolution of documented facilities (user commands, system calls, library functions) across revisions. I will thus present the early system’s defining architectural features (layering, system calls, devices as files, an interpreter, and process management) and the important ones that followed in subsequent releases: the tree directory structure, user contributed code, I/O redirection, the shell as a user program, groups, pipes, scripting, and little languages.

• Q: Why this topic?

Unix stands out as a major engineering breakthrough due to its exemplary design, its numerous technical contributions, its impact, its development model, and its widespread use. Furthermore, the design of the Unix programming environment has been characterized as one offering unusual simplicity, power, and elegance. Consequently, there are many lessons that we can learn by studying the evolution of the Unix architecture, which we can apply to the design of new systems. I often see modern systems that suffer from a bloat of architectural features and a lack of clear form on which functionality can be built. I believe that many of the modern Unix architecture defining features are excellent examples of what we should strive toward as system architects.

• Q: What do you hope to accomplish by giving this talk? What do you expect?

I’d like FOSDEM attendees to leave the talk with their mind full with architectural features of timeless quality. I want them to realize that architectural elegance isn’t derived by piling design patterns and does not need to be expensive in terms of resources. Rather, beautiful architecture can be achieved on an extremely modest scale. Furthermore, I want attendees to appreciate the importance of adopting flexible conventions rather than rigid enforcement mechanisms. Finally, I want to demonstrate through examples that the open source culture was part of Unix from its earliest days.

• Q: What are the most significant milestones in the development of Unix?

The architectural development of Unix follows a path of continuous evolution, albeit at a slowing pace, so I don’t see here the most important milestones. I would however defi