Linux refers to the family of Unix-like computer operating systems using the Linux kernel. The name "Linux" comes from the Linux kernel, originally written in 1991 by Linus Torvalds. Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers. Linux is a leading server operating system, and runs the 10 fastest supercomputers in the world

The development of Linux is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed, both commercially and 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 and supporting utilities and libraries to fulfill the distribution's intended use.

Linux is a widely ported operating system kernel. The Linux kernel runs on a highly diverse range of computer architectures: in the hand-held ARM-based iPAQ and the mainframe IBM System z9, System z10 in devices ranging from mobile phones to supercomputers.

Due to its low cost and ease of modification, an embedded Linux is often used in embedded systems. Android, which is based on a modified version of the Linux kernel, has become a major competitor of Symbian OS which is used in the majority of smartphones — 25.5% of smartphones sold worldwide during Q3 2010 were using Android (Linux variations accounted for 27.6% in total). Cell phones or PDAs running on Linux and built on open source platform became a trend from 2007, like Nokia N810, Openmoko's Neo1973, Motorola RAZR2 v8, Motorola ROKR E8, Motorola MING series, Motorola ZINE and Google Android with a modified Linux Kernel . Adding to the trend, Palm, (Later acquired by HP), produced its revamped new Operating System, called webOS, and introduced the Palm Pre, Palm Pre Plus, Palm Pixi, Palm Pixi Plus, all using a modified Linux Kernel. The popular TiVo digital video recorder uses a customized version of Linux.Several network firewall and router standalone products, including several from Cisco/Linksys, use Linux internally, using its advanced firewall and routing capabilities. The Korg OASYS and the Yamaha Motif XS music workstations,Yamaha S90XS/S70XS synthesizers, Yamaha Motif-Rack XS tone generator module, and Roland RD-700GX digital piano also run Linux. Furthermore, Linux is used in the leading stage lighting control system, FlyingPig/HighEnd WholeHogIII Console

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A summarized history of Unix-like operating systems showing Linux's origins. Of note, Linux shares similar architectural designs and concepts (as part of the POSIX standard) but does not share non-free source code with the original Unix or MINIX.
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Usage share of web client operating systems. (Source: Median values from Usage share of operating systems for December 2010.)
  Windows XP (44.0%)
  Windows 7 (24.23%)
  Windows Vista (16.74%)
  Mac OS X (6.82%)
  iOS (iPhone) (1.94%)
  Linux (1.53%)


Above pictures from left to right:
Picture 1: GNOME
Picture 2: KDE Plasma Desktop
Picture 3: LXDE
Picture 4: Xfce

To the left:
Upper picture: Servers designed for Linux
Lower picture: The Oak Ridge National Laboratory's Jaguar supercomputer, until recently the world's fastest supercomputer. It uses the Cray Linux Environment as its operating system.