Summary
Highlights
Linux is a pervasive operating system kernel used in Android, desktops, laptops, Chrome OS, servers, and Raspberry Pi. Unix, sounding similar, raises questions about their relationship. This video explains the difference between Unix and Linux.
Unix was invented by Ken Thompson and Dennis Ritchie, visionaries in computing. They were part of the Multics project, a multi-program operating system. Frustrated with Multics, they developed an alternative, initially called 'Unics' for its single-program capability, which later became 'Unix' written in the C programming language.
AT&T, initially restricted from selling software, licensed Unix source code to universities. The University of California at Berkeley developed its own version, BSD. When AT&T entered the computer market, it released System V. This led to two main Unix branches: System V (e.g., HP-UX, Solaris) and BSD (e.g., Ultrix). Networking features initially developed in BSD were later incorporated into System V.
The BSD version of Unix gradually replaced AT&T components with its own, leading to a lawsuit between the University of California and AT&T. The lawsuit was dropped, resulting in BSD 4.4 Lite, a version free from AT&T's original code. This paved the way for FreeBSD and contributed to macOS. The conflicts solidified the 'Unix philosophy' emphasizing single-purpose programs and inter-program communication through pipes, and established standards like POSIX for compatibility.
Simultaneously, Richard Stallman initiated the GNU Project (GNU's Not Unix), advocating for free software (freedom, not cost-free) and developing essential tools like the GNU C compiler. Andrew Tannenbaum created MINIX, an educational operating system for teaching OS design principles. These projects provided crucial foundations for future developments.
In the early 1990s, Linus Torvalds, inspired by MINIX and Unix, developed his own operating system kernel, Linux. It ran on affordable 386 PCs, making it accessible. Linux leveraged GNU tools and adopted the Unix philosophy. By 1992, the X Window System was ported, enabling graphical desktops. Linux quickly gained popularity, supported by the GNU Public License (GPL) which fostered open-source contributions.
Today, Linux is widespread, powering Android devices (millions of users), 60% of internet web servers, and Chrome OS. Linux is not a version of Unix but a 'unix-like' or 'Unix clone' operating system. It shares the philosophy and programming environment of Unix but not its original source code. Modern macOS is also considered a popular version of Unix, partly stemming from BSD.
Despite their separate origins, Linux's design still references Unix for its philosophical approach and interfaces. The video demonstrates this compatibility by successfully compiling and running a 30-year-old Unix backgammon game on a Raspberry Pi running Linux, highlighting the source code compatibility between them.
Linux distributions (Red Hat, Fedora, Ubuntu) comprise the Linux kernel along with various tools, desktops (KDE, Gnome), and applications (LibreOffice, Chrome). Similarly, FreeBSD distributions include the FreeBSD kernel (based on BSD 4.4 Lite) and a suite of desktops and applications. Both embody the broader free software ecosystem.
Unix was a commercial product from AT&T, with its licensed source code leading to operating systems like FreeBSD and macOS. Linux was developed as a Unix clone, adopting its philosophy but not its original code, and it's now a dominant open-source force, especially in servers and smartphones. The success of free software is a key takeaway.