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Wednesday, December 7, 2011

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds. Linux system distributions may vary in many details of system operation, configuration, and software package selections.

Linux runs on a wide variety of computer hardware, including mobile phones, tablet computers, network routers, televisions, video game consoles, desktop computers, mainframes and supercomputers. Linux is a leading server operating system, and runs the 10 fastest supercomputers in the world. In addition, more than 90% of today's supercomputers run some variant of Linux.

The development of Linux is one of the most prominent examples of free and open source software collaboration: the underlying source code may be used, modified, and distributed—commercially or non-commercially—by anyone under licenses such as the GNU General Public License. Typically Linux is packaged in a format known as a Linux distribution for desktop and server use. Some popular mainstream Linux distributions include Debian (and its derivatives such as Ubuntu), Fedora and openSUSE. Linux distributions include the Linux kernel, supporting utilities and libraries and usually a large amount of application software to fulfill the distribution's intended use.

A distribution oriented toward desktop use may include the X Window System and an accompanying desktop environment such as GNOME or KDE Plasma. Other distributions may include a less resource intensive desktop such as LXDE or Xfce for use on older or less-powerful computers. A distribution intended to run as a server may omit any graphical environment from the standard install and instead include other software such as the Apache HTTP Server and a SSH server like OpenSSH. Because Linux is freely redistributable, it is possible for anyone to create a distribution for any intended use. Commonly used applications with desktop Linux systems include the Mozilla Firefox web browser, the OpenOffice.org or LibreOffice office application suites, and the GIMP image editor.

The main supporting user space system tools and libraries from the GNU Project (announced in 1983 by Richard Stallman) are the basis for the Free Software Foundation's preferred name GNU/Linux.

History About Linux:
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. It was first released in 1971 and was initially entirely written in assembly language, a common practice at the time. Later, in a key pioneering approach in 1973, Unix was re-written in the programming language C by Dennis Ritchie (with exceptions to the kernel and I/O). The availability of an operating system written in a high-level language allowed easier portability to different computer platforms. With a legal glitch forcing AT&T to license the operating system's source code to anyone who asked, Unix quickly grew and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs. Free of the legal glitch 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. 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. Linus Torvalds has said that if the GNU kernel had been available at the time (1991), he would not have decided to write his own.

Although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD and FreeBSD descended, predated that of Linux. Linus Torvalds has said that if 386BSD had been available at the time, he probably would not have created Linux.

MINIX is an inexpensive minimal Unix-like operating system, designed for education in computer science, written by Andrew S. Tanenbaum. Starting with version 3, MINIX was free and redesigned for “serious” use.

In 1991 while attending the University of Helsinki, Torvalds, curious about the operating systems [27] and frustrated by the licensing of MINIX limiting it to educational use only (which prevented any commercial use), began to work on his own operating system 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 it became possible for Linux to be developed under itself. Also GNU applications replaced all MINIX ones, because with code from the GNU system freely available, it was advantageous if this could be used with the fledgling operating system. Code licensed under the GNU GPL can be used in other projects, so long as they also are released under the same or a compatible license. In order to make Linux available for commercial use, Torvalds initiated a switch from his original license (which prohibited commercial redistribution) to the GNU GPL. Developers worked to integrate GNU components with Linux to make a fully functional and free operating system.

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