The Unix operating system was conceived and implemented in 1969 at AT&T’s Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. First released in 1971, Unix was written entirely in assembly language as it was common practice at the time. Later, in a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie (with exceptions to the kernel and I/O). The availability of a high-level language implementation of Unix made its porting to different computer platforms easier.
Due to an earlier antitrust case forbidding it from entering the computer business, AT&T was required to license the operating system’s source code to anyone who asked. As a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs; freed of the legal obligation requiring free licensing, Bell Labs began selling Unix as a proprietary product.
The GNU Project, started in 1983 by Richard Stallman, had the goal of creating a “complete Unix-compatible software system” composed entirely of free software. Stallman decided to call this operating system GNU (a recursive acronym meaning “GNU’s not Unix“), basing its design on that of Unix, a proprietary operating system.Work began in 1984. Later, in 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete.
MINIX was created by a computer science professor Andrew S. Tanenbaum and released in 1987 as a minimal Unix-like operating system targeted at students and others who wanted to learn the operating system principles. Although the complete source code of MINIX was freely available, the licensing terms prevented it from being free software until the licensing changed in April 2000.
In 1991, while attending the University of Helsinki, Finland Linus Torvalds became curious about operating systems and frustrated by the licensing of MINIX, which at the time limited it to educational use only. He began to work on his own operating system kernel, which eventually became the Linux kernel.
Torvalds began the development of the Linux kernel on MINIX and applications written for MINIX were also used on Linux. Later, Linux matured and further Linux kernel development took place on Linux systems.GNU applications also replaced all MINIX components, because it was advantageous to use the freely available code from the GNU Project with the fledgling operating system; code licensed under the GNU GPL can be reused in other projects as long as they also are released under the same or a compatible license. Torvalds initiated a switch from his original license, which prohibited commercial redistribution, to the GNU GPL. Developers worked to integrate GNU components with the Linux kernel, making a fully functional and free operating system.
A Linux-based system is a modular Unix-like operating system, deriving much of its basic design from principles established in Unix during the 1970s and 1980s. Such a system uses a monolithic kernel, the Linux kernel, which handles process control, networking, access to the peripherals, and file systems. Device drivers are either integrated directly with the kernel, or added as modules that are loaded while the system is running.
Separate projects that interface with the kernel provide much of the system’s higher-level functionality. The GNU userland is an important part of most Linux-based systems, providing the most common implementation of the C library, a popular CLI shell, and many of the common Unix tools which carry out many basic operating system tasks. The graphical user interface (or GUI) used by most Linux systems is built on top of an implementation of the X Window System.
Linus Torvalds had wanted to call his invention Freax, a portmanteau of “free”, “freak”, and “x” (as an allusion to Unix). During the start of his work on the system, he stored the files under the name “Freax” for about half of a year. Torvalds had already considered the name “Linux,” but initially dismissed it as too egotistical.
Tux is a penguin character and the official mascot of the Linux kernel. Originally created as an entry to a Linux logo competition, Tux is the most commonly used icon for Linux, although different Linux distributions depict Tux in various styles. The character is used in many other Linux programs and as a general symbol of Linux. Tux was created by Larry Ewing in 1996 after an initial suggestion made by Alan Cox and further refined by Linus Torvalds on the Linux kernel mailing list. The first person to call the penguin “Tux” was James Hughes, who said that it stood for “(T)orvalds (U)ni(X)”. However, tux is also an abbreviation of tuxedo, the outfit which springs to mind when one sees a penguin.
Eric S. Raymond wrote an essay named The Cathedral and the Bazaar: Musings on Linux and Open Source by an Accidental Revolutionary (abbreviated CatB) on software engineering methods, based on his observations of the Linux kernel development process and his experiences managing an open source project, fetchmail. It examines the struggle between top-down and bottom-up design.
The essay contrasts two different free software development models:
- The Cathedral model, in which source code is available with each software release, but code developed between releases is restricted to an exclusive group of software developers. GNU Emacs and GCC were presented as examples.
- The Bazaar model, in which the code is developed over the Internet in view of the public. Raymond credits Linus Torvalds, leader of the Linux kernel project, as the inventor of this process. Raymond also provides anecdotal accounts of his own implementation of this model for the Fetchmail project.
Due in part to the popularity of his essay, Raymond became a prominent voice in the open source movement. He co-founded the Open Source Initiative in 1998, taking on the self-appointed role of ambassador of open source to the press, business and public. The internal white paper by Frank Hecker that led to the release of the Mozilla (then Netscape) source code in 1998 cited The Cathedral and the Bazaar as “independent validation” of ideas proposed by Eric Hahn and Jamie Zawinski. Hahn would later describe the 1999 book as “clearly influential”.
Raymond coined an aphorism he dubbed “Linus’ Law”, inspired by Linus Torvalds: “Given enough eyeballs, all bugs are shallow“.
Adoption of Linux in production environments, rather than being used only by hobbyists, started to take off first in the mid-1990s in the supercomputing community, where organizations such as NASA started to replace their increasingly expensive machines with clusters of inexpensive commodity computers running Linux.
In 1993 Bob Young incorporated the ACC Corporation, a catalog business that sold Linux and Unix software accessories. In 1994 Marc Ewing created his own Linux distribution, which he named Red Hat Linux (Ewing had worn a red Cornell University lacrosse hat, given to him by his grandfather, while attending Carnegie Mellon University). Ewing released the software in October, and it became known as the Halloween release. Young bought Ewing’s business in 1995, and the two merged to become Red Hat Software, with Young serving as CEO. Red Hat went public on August 11, 1999, achieving the eighth-biggest first-day gain in the history of Wall Street.
Debian was first announced in 1993 by Ian Murdock, and the first stable release was made in 1996. The development is carried out over the Internet by a team of volunteers guided by a project leader and three foundational documents: the Debian Social Contract, the Debian Constitution, and the Debian Free Software Guidelines. As one of the earliest Linux distributions, it was envisioned that Debian was to be developed openly in the spirit of the GNU Project. This vision drew the attention and support of the Free Software Foundation, which sponsored the project for one year from November 1994 to November 1995.
Debian has three main branches: Stable, Testing and Unstable.
The Debian Stable distribution is one of the most popular for personal computers and network servers, and has been used as a base for several other Linux distributions including Ubuntu, Linux Mint, Kali Linux and several others.
The distribution that made Linux to penetrate into the Desktop market and captured the larger audience of world was Ubuntu. It is based on free software and named after the Southern African philosophy of ubuntu (literally, “human-ness”), which often is translated as “humanity towards others” or “the belief in a universal bond of sharing that connects all humanity”.
The first release of Ubuntu happened on October 2004. Ubuntu is built on Debian’s architecture and infrastructure, to provide Linux server, desktop, phone, tablet and TV operating systems. Ubuntu releases updated versions predictably every six months, and each release receives free support for nine months (eighteen months prior to 13.04) with security fixes, high-impact bug fixes and conservative, substantially beneficial low-risk bug fixes.
Ubuntu packages are based on packages from Debian’s unstable branch. Both distributions use Debian’s deb package format and package management tools (APT and Ubuntu Software Center). Development of Ubuntu is led by UK-based Canonical Ltd., a company owned by South African entrepreneur Mark Shuttleworth.
Linux democratized the OS spawning specialized operating systems across several domains. Kali Linux for example is a Debian-derived Linux distribution designed for digital forensics and penetration testing. Kali Linux is preinstalled with over 600 penetration-testing programs and is the swiss army knife of security professionals and hackers alike.
Today, Linux systems are used in every domain, from embedded systems to supercomputers, and have secured a place in server installations often using the popular LAMP (Linux+Apache+MySQL+PHP) application stack. Use of Linux distributions in home and enterprise desktops has been growing. Linux distributions have also become popular in the netbook market, with many devices shipping with customized Linux distributions installed, and Google releasing their own Chrome OS designed for netbooks. Linux’s greatest success in the consumer market is perhaps the mobile device market, with Android being one of the most dominant operating systems on smartphones and very popular on tablets and, more recently, on wearables.
Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries.
Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.
Directed by J. T. S. Moore, the film features interviews with prominent hackers and entrepreneurs including Richard Stallman, Michael Tiemann, Linus Torvalds, Larry Augustin, Eric S. Raymond, Bruce Perens, Frank Hecker and Brian Behlendorf.