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{{Infobox OS
| bodystyle = width:325px
| name = Linux
| logo = [[File:Tux.svg|150px]]
| screenshot =
| caption = [[Tux]] the [[penguin]], mascot of Linux<ref name="LinuxOnLine2008">{{cite web
| url = http://www.linux.org/info/logos.html
| title = Linux Logos and Mascots
| accessdate = 2009-08-11
| last = Linux Online
| authorlink =
| year = 2008
}}</ref>
| family = [[Unix-like]]
| website = [http://www.kernel.org/ kernel.org]
| developer = [[GNU Project]], [[Linus Torvalds]] and many others
| source model = [[Free and open source software]]
| frequently updated = yes <!-- Release version update? Don't edit this page, just click on the version number! -->
| marketing target = Desktops, servers, embedded devices
| kernel type = [[Monolithic kernel|Monolithic]]
| ui = {{nowrap|[[Graphical User Interface|Graphical]] ([[X Window System]])}} {{nowrap|and [[command-line interface]]}}
| programmed in = [[Assembly language]], [[C (programming language)|C]]
| prog language = Many
| userland = [[GNU Core Utilities|GNU]] and others
| supported platforms = [[DEC Alpha]], [[ARM architecture|ARM]], [[AVR32]], [[Blackfin]], [[ETRAX CRIS]], [[FR-V]], [[H8/300]], [[Itanium]], [[M32R]], [[m68k]], [[Microblaze]], [[MIPS architecture|MIPS]], [[MN103]], [[PA-RISC]], [[PowerPC]], [[s390]], [[S+core]], [[SuperH]], [[SPARC]], [[TILE64]], [[Unicore32]], [[x86]], [[Xtensa]] <!-- Do not include 64 bit extensions of 32 bit ISAs, e.g. sparc64, ppc64, x86-64, etc. -->
| license = Various including [[GNU General Public License]], [[BSD License]], [[Apache License]], [[MIT License]], and others<ref>{{cite web | title = Debian GNU/Linux Licenses – Ohloh | url = https://www.ohloh.net/p/debian/analyses/latest | publisher = ohloh.net | accessdate = 2009-03-27 }}</ref>
| language = Multilingual
| updatemodel =
| working state = Current
}}
{{Listen
| filename = Linus-pronounces-linux.ogg
| title = How Linus Torvalds pronounces Linux
| format = [[Ogg]]
}}
'''Linux''' (commonly {{IPAc-en|icon|ˈ|l|ɪ|n|ə|k|s}} {{respell|LIN|əks}} in [[English language|English]],<ref>{{cite web|url=http://safalra.com/science/linguistics/linux-pronunciation/|title=Pronunciation of ‘Linux’|last=Safalra|date=2007-04-14|work=Safalra’s Website|accessdate=2009-09-15}}</ref><ref name="Foldoc09Jun06">{{cite web|url = http://foldoc.org/linux|title = Linux|accessdate = 2009-09-15|last = Free On-Line Dictionary of Computing|authorlink = |year = 2006|month = June}}</ref> also {{pron-en|ˈlɪnʊks}} {{respell|LIN|uuks}}<ref>Torvalds used {{IPAc-en|icon|ˈ|l|ɪ|n|ʊ|k|s}} in English.<br />{{cite newsgroup | newsgroups = comp.os.linux | title = Re: How to pronounce "Linux"? | id = 1992Apr23.123216.22024@klaava.Helsinki.FI | date = 23 April 1992 | accessdate = 2007-01-09 }}<br /> Torvalds recorded himself pronouncing the name during the 1990s. ({{IPA|/ˈlɪnʊks/}}: {{cite web | url = http://www.paul.sladen.org/pronunciation/ | title = How to pronounce Linux? | accessdate = 2006-12-17 }}) and in Swedish ({{IPA|/ˈlɪːnɤks/}}: {{cite web | url = http://www.kernel.org/pub/linux/kernel/SillySounds/ | title = Linus pronouncing Linux in English and Swedish | accessdate = 2007-01-20 }})</ref> in Europe) refers to the family of [[Unix-like]] computer [[operating system]]s using the [[Linux kernel]]. Linux can be installed on a wide variety of computer [[hardware]], ranging from [[mobile phone]]s, [[tablet computer]]s, [[router]]s, and [[video game console]]s, to [[mainframe computer|mainframes]] and [[supercomputer]]s.<ref name="LinuxDevices">{{cite web|url = http://www.trl.ibm.com/projects/ngm/wp10_e.htm|title = Linux Watch|accessdate = 2009-09-29|last = [[IBM]]|authorlink = |year = 2001|month = October}}</ref><ref name="IBMLinuxWatch">{{cite web|url = http://www.linuxfordevices.com/c/a/News/Trolltech-rolls-complete-Linux-smartphone-stack/|title = Trolltech rolls "complete" Linux smartphone stack|accessdate = 2009-09-29|last = Linux Devices|authorlink = |year = 2010|month = January}}</ref><ref>{{cite web | title = IBM's newest mainframe is all Linux | url = http://www.computerworld.com/s/article/9142007/IBM_s_newest_mainframe_is_all_Linux_ | last = Computerworld | first = Patrick Thibodeau | accessdate = 2009-02-22 }}</ref><ref>{{cite news | title = Linux rules supercomputers | url = http://www.forbes.com/home/enterprisetech/2005/03/15/cz_dl_0315linux.html | last = Lyons | first = Daniel | accessdate = 2007-02-22 | work=Forbes}}</ref> Linux is a leading [[server (computing)|server]] operating system, and runs the 10 fastest [[supercomputers]] in the world.<ref>{{cite web|author=Henry Burkhardt, KSR |url=http://www.top500.org/lists/2010/06 |title=June 2010 | TOP500 Supercomputing Sites |publisher=Top500.org |date= |accessdate=2010-10-30}}</ref>
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 (operating system)|Debian]] (and its derivatives such as [[Ubuntu (operating system)|Ubuntu]]), [[Fedora (operating system)|Fedora]] and [[openSUSE]]. Linux distributions include the Linux kernel and supporting [[system utility|utilities]] and [[library (computer science)|libraries]] to fulfill the distribution's intended use.
A distribution oriented toward desktop use may include the [[X Window System]], the [[GNOME]] and [[KDE Plasma Workspaces|KDE Plasma]] [[desktop environment]]s. 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 name "Linux" comes from the Linux kernel, originally written in 1991 by [[Linus Torvalds]]. 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 naming controversy|GNU/Linux]]''.<ref name="lsag">{{cite book | url = http://www.tldp.org/LDP/sag/html/sag.html#GNU-OR-NOT | title = Linux System Administrator's Guide | chapter = 1.1 | edition = version 0.9 | year = 2004 | accessdate = 2007-01-18 | first = Alex | last = Weeks }}</ref><ref name="gnu_homepage">{{cite web|url=http://www.gnu.org/ |title=The GNU Operating System |publisher=Gnu.org |accessdate=2009-04-17}}</ref>
==History==
===Unix===
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 (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 [[porting|portability]] to different computer platforms. With a legal glitch forcing AT&T to license the operating system's source code to anyone who asked,<ref name="faqs.org">{{cite web|url=http://www.faqs.org/docs/artu/ch02s01.html |title=Origins and History of Unix, 1969–1995 |publisher=Faqs.org |date= |accessdate=2010-11-09}}</ref> 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 software|proprietary]] product.
[[Image:Richard Matthew Stallman cropped.jpeg|upright|thumb|left|[[Richard Stallman]], founder of the [[GNU project]]]]
===GNU===
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.<ref name="gnu_announce">{{cite web|url=http://www.gnu.org/gnu/initial-announcement.html |title=About the GNU Project – Initial Announcement |publisher=Gnu.org |date=2008-06-23 |accessdate=2009-03-09}}</ref> 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, [[compiler]]s, [[text editor]]s, a [[Unix shell]], and a windowing system) were completed, although low-level elements such as [[device driver]]s, [[daemon (computer software)|daemons]], and the [[kernel (computer science)|kernel]] were stalled and incomplete.<ref name="gnu history">{{cite web|url=http://www.gnu.org/gnu/gnu-history.html |title=Overview of the GNU System |publisher=Gnu.org |date= |accessdate=2009-03-09}}</ref> 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.<ref>{{cite web | url = http://www.dina.dk/~abraham/Linus_vs_Tanenbaum.html | title = Linus vs. Tanenbaum debate }}</ref>
===BSD===
Although not released until 1992 due to [[Berkeley Software Distribution#Net/2 and legal troubles|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.<ref name="meta">{{cite web|url=http://gondwanaland.com/meta/history/interview.html|title=The Choice of a GNU Generation – An Interview With Linus Torvalds|last=Linksvayer|first=Mike|year=1993|work=Meta magazine|accessdate=2009-01-20}}</ref>
===MINIX===
{{double image|right|AndrewTanenbaum2.png|130|Linus Torvalds cropped.jpeg|150|[[Andrew S. Tanenbaum]] (left), author of the [[MINIX]] operating system and [[Linus Torvalds]] (right), principal author of the [[Linux kernel]]}}
[[MINIX]] is an inexpensive minimal [[Unix-like]] operating system, designed for education in computer science, written by [[Andrew S. Tanenbaum]]. Starting with [[MINIX 3|version 3, MINIX]] was [[free software|free]] and redesigned for “serious” use.
In 1991 while attending the [[University of Helsinki]], Torvalds, curious about the operating systems <ref>{{cite newsgroup | title = What would you like to see most in minix? | newsgroup = comp.os.minix | id = 1991Aug25.205708.9541@klaava.Helsinki.FI | url = http://groups.google.com/group/comp.os.minix/msg/b813d52cbc5a044b | last = Torvalds | first = Linus | accessdate = 2006-09-09 }}</ref> 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.<ref>{{cite news | title = Chicken and egg: How was the first linux gcc binary created?? | newsgroup = comp.os.minix | url = http://groups.google.com/group/comp.os.linux/msg/4ae6db18d3f49b0e }}</ref> 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 the Linux available for commercial use, Torvalds initiated a switch from his original license (which prohibited commercial redistribution) to the GNU GPL.<ref>{{cite web | title = Release notes for Linux v0.12 | first = Linus | last = Torvalds | url = http://www.kernel.org/pub/linux/kernel/Historic/old-versions/RELNOTES-0.12 | authorlink = Linus Torvalds | date = 1992-01-05 | accessdate = 2007-07-23 | publisher = Linux Kernel Archives | quote = The Linux copyright will change: I've had a couple of requests to make it compatible with the GNU copyleft, removing the “you may not distribute it for money” condition. I agree. I propose that the copyright be changed so that it confirms to GNU ─ pending approval of the persons who have helped write code. I assume this is going to be no problem for anybody: If you have grievances ("I wrote that code assuming the copyright would stay the same") mail me. Otherwise The GNU copyleft takes effect since the first of February. If you do not know the gist of the GNU copyright ─ read it. }}</ref> Developers worked to integrate GNU components with Linux to make a fully functional and free operating system.<ref name="gnu history"/>
===Commercial and popular uptake===
[[File:Ubuntu 11.04 Installation SS.png|thumb|Ubuntu is a popular distribution of Linux]]
{{Main|Linux adoption}}
Today, Linux distributions are used in every ___domain, from [[embedded system]]s to [[supercomputer]]s,<ref>{{cite web | title = Linux system development on an embedded device | url = http://www-128.ibm.com/developerworks/library/l-embdev.html | first = Anand | last = Santhanam | coauthors = Vishal Kulkarni | work = DeveloperWorks | publisher = IBM | date = 1 March 2002 | accessdate = 2007-07-26 }}</ref><ref>{{cite news| last = Lyons | first = Daniel| title = Linux rules supercomputers | url = http://www.forbes.com/home/enterprisetech/2005/03/15/cz_dl_0315linux.html | accessdate = 2007-02-22 | work=Forbes}}</ref> and have secured a place in [[server (computing)|server]] installations often using the popular [[LAMP (software bundle)|LAMP]] application stack.<ref>{{cite web| last = Schrecker| first = Michael| title = Turn on Web Interactivity with LAMP | url = http://www.techsoup.org/learningcenter/webbuilding/page5067.cfm | accessdate = 2007-02-22}}</ref> Use of Linux distributions in home and enterprise desktops has been growing.<ref name="galli2007">{{cite news | first=Peter | last=Galli | coauthors= | title=Vista Aiding Linux Desktop, Strategist Says | date=2007-08-08 | publisher=Ziff Davis Enterprise Inc. | url =http://www.eweek.com/c/a/Linux-and-Open-Source/Vista-Aiding-Linux-Desktop-Strategist-Says/ | work =eWEEK | pages = | accessdate = 2007-11-19 | language = }}</ref><ref name="paul2007">{{cite news | first=Ryan | last=Paul | coauthors= | title=Linux market share set to surpass Win 98, OS X still ahead of Vista | date=2007-09-03 | publisher=Ars Technica, LLC | url =http://arstechnica.com/news.ars/post/20070903-linux-marketshare-set-to-surpass-windows-98.html | work =Ars Technica | pages = | accessdate = 2007-11-19 | language = }}</ref><ref name="beer2007">{{cite news | first=Stan | last=Beer | coauthors= | title=Vista to play second fiddle to XP until 2009: Gartner | date=2007-01-23 | publisher=iTWire | url =http://www.itwire.com.au/content/view/8842/53/ | work =iTWire | pages = | accessdate = 2007-11-19 | language = }}</ref><ref name="applications2007">{{cite web|url=http://marketshare.hitslink.com/report.aspx?qprid=2&qpmr=15&qpdt=1&qpct=3&qptimeframe=Y |title=Operating System Marketshare for Year 2007 |accessdate=2007-11-19 |date=2007-11-19 |work=Market Share |publisher=Net Applications }}</ref><ref name="xitimonitor2007">{{cite news | first= | last= | coauthors= | title=Vista slowly continues its growth; Linux more aggressive than Mac OS during the summer | date=2007-09-24 | publisher=AT Internet/XiTi.com | url =http://www.xitimonitor.com/en-us/internet-users-equipment/operating-systems-august-2007/index-1-2-7-107.html | work =XiTiMonitor | pages = | accessdate = 2007-11-19 | language = }}</ref><ref name="globalstats2007">{{cite web|url=http://www.w3counter.com/globalstats.php |title=Global Web Stats |accessdate=2007-11-19 |date=2007-11-10 |work=W3Counter |publisher=Awio Web Services LLC }}</ref><ref name="zeitgeist2004">{{cite web|url=http://www.google.com/press/zeitgeist/zeitgeist-jun04.html |title=June 2004 Zeitgeist |accessdate=2007-11-19 |date=2004-08-12 |work=Google Press Center |publisher=Google Inc. }}</ref> They have also gained popularity with various local and national governments. The federal government of Brazil is well known for its support for Linux.<ref>{{cite web | url = http://news.cnet.com/Brazils-love-of-Linux/2009-1042_3-6245409.html | title = Brazil's love of Linux | accessdate = 2009-02-21 }}</ref><ref>{{cite news | url = http://news.bbc.co.uk/2/hi/business/3445805.stm | title = Brazil falls in love with Linux | accessdate = 2009-02-21 | work=BBC News | date=2004-02-01 | first=Mark | last=Ashurst}}</ref> News of the Russian military creating their own Linux distribution has also surfaced, and has come to fruition as the G.H.ost Project.<ref>{{cite web | url = http://www.osor.eu/news/lv-minister-open-standards-improve-efficiency-and-transparency | title = LV: Minister: "Open standards improve efficiency and transparency" | accessdate = 2009-02-21 }}</ref> The Indian state of [[Kerala]] has gone to the extent of mandating that all state high schools run Linux on their computers.<ref>{{cite web | url = http://www.businessweek.com/globalbiz/content/sep2006/gb20060921_463452.htm | title = Linux Spreads its Wings in India | accessdate = 2009-02-21 }}</ref><ref>{{cite web | url = http://www.indianexpress.com/news/kerala-shuts-windows-schools-to-use-only-linux/280323/0 | title = Kerala shuts windows, schools to use only Linux | accessdate = 2009-06-22 }}</ref> [[People's Republic of China|China]] uses Linux exclusively as the operating system for its [[Loongson]] processor family to achieve technology independence.<ref>{{cite web | url = http://www.mdronline.com/watch/watch_Issue.asp?Volname=Issue+%23110308&on=1 | title = China’s Microprocessor Dilemma | accessdate = 2009-04-15 | publisher = [[Microprocessor Report]] }}</ref> In [[Spain]] some regions have developed their own Linux distributions, which are widely used in education and official institutions, like [[gnuLinEx]] in [[Extremadura]] and [[Guadalinex]] in [[Andalusia]]. [[Portugal]] is also using its own Linux distribution [[Caixa Mágica]], used in the Magalhães netbook<ref>{{cite web | url = http://www.caixamagica.pt/pag/f_notc00.php?id=213 | title = Magalhães equipped with Linux Caixa Mágica}}</ref> and the e-escola government program.<ref>{{cite web | url = http://www.caixamagica.pt/pag/f_notc00.php?id=204 | title = Oferta CM no programa e-Escolas surpreende o mercado}}</ref> [[France]] and [[Germany]] have also taken steps towards the adoption of Linux.<ref>{{cite web | url = http://seattlepi.com/business/48925_linuxop01.shtml | title = Some countries are choosing Linux systems over Microsoft | accessdate = 2009-02-21 }}</ref>
Linux distributions have also become popular in the [[netbook]] market, with many devices such as the [[Eee pc|ASUS Eee PC]] and [[Aspire One|Acer Aspire One]] shipping with customized Linux distributions installed.<ref>{{cite news | url = http://www.guardian.co.uk/technology/2009/may/28/netbooks-sales | title = Are netbooks losing their shine? | accessdate = 2010-06-02 | ___location=London | date=2009-05-28 | work=The Guardian | first=Jack | last=Schofield}}</ref>
===Current development===
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 distribution]]s.
==Design==
A Linux-based system is a modular [[Unix-like]] operating system. It derives 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, and [[peripheral]] and [[file system]] access. [[Device drivers]] are either integrated directly with the kernel or added as modules 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 (computing)|userland]] is an important part of most Linux-based systems, providing the most common implementation of the [[C standard library|C library]], a popular [[shell (computing)|shell]], and many of the common [[Unix tool]]s 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]].
===User interface===
{{See also|User interface}}
Users operate a Linux-based system through a [[command line interface]] (CLI), a [[graphical user interface]] (GUI), or through controls attached to the associated hardware, which is common for embedded systems. For desktop systems, the default mode is usually a graphical user interface, by which the CLI is available through [[terminal emulator]] windows or on a separate [[virtual console (PC)|virtual console]]. Most low-level Linux components, including the GNU [[userland (computing)|userland]], use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple [[inter-process communication]]. A graphical [[terminal emulator]] program is often used to access the CLI from a Linux desktop. A Linux system typically implements a CLI by a [[shell (computing)|shell]], which is also the traditional way of interacting with a Unix system. A Linux distribution specialized for servers may use the CLI as its only interface.
On desktop systems, the most popular user interfaces are the extensive [[desktop environment]]s [[KDE Plasma Desktop]], [[GNOME]], and [[Xfce]],<ref>{{cite web | title = Debian popularity-contest program information | url = http://times.debian.net/1092-30000-popcon-submissions }}</ref> though a variety of additional user interfaces exist. Most popular user interfaces are based on the [[X Window System]], often simply called "X". It provides [[network transparency]] and permits a graphical application running on one system to be displayed on another where a user may interact with the application.<ref name="manX">Manual page for "X" (xorg-docs 1:1.4-4 on Debian)</ref>
Other GUIs may be classified as simple [[X window manager]]s, such as [[FVWM]], [[Enlightenment (window manager)|Enlightenment]], and [[Window Maker]], which provide a [[minimalism (computing)|minimalist]] functionality with respect to the desktop environments. A window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X Window System. The desktop environments include window managers as part of their standard installations ([[Metacity]] for GNOME, [[Kwin]] for KDE, [[Xfwm]] for Xfce as of 2010) although users may choose to use a different window manager if preferred.
==Development==
[[File:Unix history.svg|thumb|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]].]]
{{Main|Linux distribution}}
The primary difference between Linux and many other popular contemporary operating systems is that the [[Linux kernel]] and other components are [[free software|free]] and [[open source software]]. Linux is not the only such operating system, although it is by far the most widely used.<ref name="MarketShare09NOV">{{cite web|url = http://marketshare.hitslink.com/operating-system-market-share.aspx?qprid=8|title = Operating System Market Share|accessdate = 2009-12-11|last = Operating System Market Share |authorlink = |year = 2009|month = November}}</ref>
Some [[free software license|free]] and [[open source license|open source]] software licenses are based on the principle of [[copyleft]], a kind of reciprocity: any work derived from a [[copyleft]] piece of software must also be copyleft itself. The most common free software license, the [[GNU GPL]], is a form of [[copyleft]], and is used for the Linux kernel and many of the components from the [[GNU project]].
Linux based distributions are intended by developers for [[interoperability]] with other operating systems and established computing standards. Linux systems adhere to [[POSIX]],<ref>{{cite web | url = http://www.ukuug.org/newsletter/linux-newsletter/linux@uk21/posix.shtml | title = POSIX.1 (FIPS 151-2) Certification }}</ref> [[Single UNIX Specification|SUS]],<ref>{{cite web | title = How source code compatible is Debian with other Unix systems? | url = http://www.debian.org/doc/FAQ/ch-compat.en.html#s-otherunices | work = Debian FAQ | publisher = the Debian project }}</ref> [[International Organization for Standardization|ISO]], and [[American National Standards Institute|ANSI]] standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.<ref>{{cite web | url = http://www.linuxjournal.com/article/0131 | title = Certifying Linux }}</ref>
Free software projects, although developed in a [[collaboration|collaborative]] fashion, are often produced independently of each other. The fact that the software licenses explicitly permit redistribution, however, provides a basis for larger scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a [[Linux distribution]].
A [[Linux distribution]], commonly called a "distro", is a project that manages a remote collection of system software and application software packages available for download and installation through a network connection. This allows the user to adapt the operating system to his/her specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more generally integration of the different software packages into a coherent whole. Distributions typically use a [[package manager]] such as [[dpkg]], [[Synaptic (software)|Synaptic]], [[YAST]], or [[Portage (software)|Portage]] to install, remove and update all of a system's software from one central ___location.
===Community===
{{See also|Free software community|Linux User Group}}
A distribution is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis, [[Debian]] being a well-known example. Others maintain a community version of their commercial distributions, as [[Red Hat]] does with [[Fedora (Linux distribution)|Fedora]] and [[Novell]] does with [[openSUSE]].
In many cities and regions, local associations known as [[Linux User Group]]s (LUGs) seek to promote their preferred distribution and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. Many [[Internet]] communities also provide support to Linux users and developers. Most distributions and free software / open source projects have [[IRC]] chatrooms or [[newsgroup]]s. [[Online forum]]s are another means for support, with notable examples being [[LinuxQuestions.org]] and the various distribution specific support and community forums, such as ones for [[Ubuntu (operating system)|Ubuntu]], [[Fedora (operating system)|Fedora]], and [[Gentoo Linux|Gentoo]]. Linux distributions host [[mailing list]]s; commonly there will be a specific topic such as usage or development for a given list.
There are several technology websites with a Linux focus. Print [[magazine]]s on Linux often include [[cover disk]]s including software or even complete Linux distributions.<ref>{{cite web | url=http://www.linuxformat.co.uk/dvd/ | title=Linux Format DVD contents | author=[[Linux Format]] | accessdate=2008-01-17 |archiveurl = http://web.archive.org/web/20070807222402/http://www.linuxformat.co.uk/dvd/ |archivedate = August 7, 2007}}</ref><ref>{{cite web | url=http://www.linux-magazine.com/resources/current_issue | title=Current Issue | author=linux-magazine.com | accessdate=2008-01-17 | authorlink=Linux Magazine }}</ref>
Although [[Linux distributions]] are generally available without charge, several large corporations sell, support, and contribute to the development of the components of the system and of [[free software]]. An analysis of the Linux kernel showed 75 percent of the code from December 2008 to January 2010 was developed by programmers working for corporations, leaving about 18 percent to the traditional, open source community.<ref>{{cite web | url=http://apcmag.com/linux-now-75-corporate.htm | title=75% of Linux code now written by paid developers
| author=|work=[[APC (magazine)|APC]] | accessdate=2010-01-22 }}</ref> Some of the major corporations that contribute include [[Dell]], [[IBM]], [[Hewlett-Packard|HP]], [[Oracle Corporation|Oracle]], [[Sun Microsystems]] (now part of Oracle), [[Novell]], and [[Nokia]]. A number of corporations, notably [[Red Hat]] and [[Novell]], have built a significant business around Linux distributions.
The [[free software licenses]], on which the various software packages of a distribution built on the Linux kernel are based, explicitly accommodate and encourage commercialization; the relationship between a Linux distribution as a whole and individual vendors may be seen as [[symbiosis|symbiotic]]. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks.
Another business model is to give away the software in order to sell hardware. This used to be the norm in the computer industry, with operating systems such as [[CP/M]], [[Apple DOS]] and versions of [[Mac OS]] prior to 7.5 freely copyable (but not modifiable). As computer hardware standardized throughout the 1980s, it became more difficult for hardware manufacturers to profit from this tactic, as the OS would run on any manufacturers computer that shared the same architecture.
===Programming on Linux===
Linux distributions support dozens of [[programming language]]s. The most common collection of utilities for building both Linux applications and operating system programs is found within the [[GNU toolchain]], which includes the [[GNU Compiler Collection]] (GCC) and the [[GNU build system]].{{Citation needed|date=May 2011}} Amongst others, GCC provides compilers for [[Ada (programming language)|Ada]], [[C (programming language)|C]], [[C++]], [[Java (programming language)|Java]], and [[Fortran]]. [[Proprietary software|Proprietary]] compilers for Linux include the [[Intel C++ Compiler]], [[Sun Studio (software)|Sun Studio]], and IBM XL [[C (programming language)|C]]/[[C++]] Compiler. [[BASIC]] in the form of [[Visual Basic]] is supported in such forms as [[Gambas]], [[FreeBASIC]], and [[XBasic]].
Most distributions also include support for [[PHP]], [[Perl]], [[Ruby programming language|Ruby]], [[Python programming language|Python]] and other [[dynamic programming language|dynamic languages]]. While not as common, Linux also supports [[C Sharp (programming language)|C#]] (via [[Mono (software)|Mono]]), [[Vala (programming language)|Vala]], and [[Scheme programming language|Scheme]]. A number of [[Java Virtual Machine]]s and development kits run on Linux, including the original Sun Microsystems JVM ([[HotSpot]]), and IBM's J2SE RE, as well as many open-source projects like [[Kaffe]] and [[JikesRVM]].
The two main frameworks for developing graphical applications are those of [[GNOME]] and [[KDE]].{{Citation needed|date=May 2011}} These projects are based on the [[GTK+]] and [[Qt (toolkit)|Qt]] [[widget toolkit]]s, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of [[Integrated development environment]]s available including [[Anjuta]], [[Code::Blocks]], [[CodeLite]], [[Eclipse (computing)|Eclipse]], [[Geany]], [[ActiveState Komodo]], [[KDevelop]], [[Lazarus (software)|Lazarus]], [[MonoDevelop]], [[NetBeans]], [[Qt Creator]] and [[Omnis Studio]], while the long-established editors [[Vim (text editor)|Vim]] and [[Emacs]] remain popular.<ref>{{cite web | first = Joe | last = Brockmeier | title = A survey of Linux Web development tools | url = http://programming.linux.com/programming/05/10/03/1828224.shtml?tid=63&tid=47 | accessdate = 2006-12-16 }}</ref>
==Uses==
As well as those designed for general purpose use on desktops and servers, distributions may be specialized for different purposes including: [[computer architecture]] support, [[Embedded Linux|embedded systems]], stability, security, localization to a specific region or language, targeting of specific user groups, support for [[real-time computing|real-time]] applications, or commitment to a given desktop environment. Furthermore, some distributions deliberately include only [[free software]]. Currently, over three hundred distributions are actively developed, with about a dozen distributions being most popular for general-purpose use.<ref>{{cite web | url = http://lwn.net/Distributions/ | title = The LWN.net Linux Distribution List | accessdate = 2006-05-19 }}</ref>
Linux is a widely [[porting|ported]] operating system kernel. The Linux kernel runs on a highly diverse range of [[computer architecture]]s: in the hand-held [[ARM architecture|ARM]]-based [[iPAQ]] and the [[mainframe computer|mainframe]] [[IBM]] [[IBM System z9|System z9]], [[IBM System z9|System z10]]; in devices ranging from [[mobile phone]]s to [[supercomputer]]s.<ref>{{cite web| url = http://www.freeos.com/articles/4737/ | title = If I could re-write Linux | first = Prakash | last = Advani | date = 8 February 2004 | accessdate = 2007-01-23 | publisher = freeos.com }}</ref> Specialized distributions exist for less mainstream architectures. The [[ELKS]] kernel [[fork (software development)|fork]] can run on [[Intel 8086]] or [[Intel 80286]] [[16-bit]] microprocessors, while the [[µClinux]] kernel fork may run on systems without a [[memory management unit]]. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as [[Macintosh]] computers (with both [[PowerPC]] and [[Intel]] processors), [[Personal digital assistant|PDAs]], [[video game console]]s, [[Digital audio player|portable music players]], and [[mobile phone]]s.
There are several industry associations and hardware [[Business conference|conferences]] devoted to maintaining and improving support for diverse hardware under Linux, such as [[FreedomHEC]].
===Desktop===
{{Main|Desktop Linux}}
The popularity of Linux on standard desktop computers and laptops has been increasing over the years.<ref>[http://www.linux.org/info/index.html What is Linux]</ref> Currently most distributions include a graphical user environment, with the two most popular environments being [[GNOME]] (which can utilize additional [[Shell (computing)|shells]] such as the default [[GNOME Shell]], the [[Ubuntu (operating system)|Ubuntu]] [[Unity (desktop environment)|Unity]]), and the [[KDE Plasma Desktop]]. All three are mature and support a wide variety of languages. {{Citation needed|date=May 2011}}
The performance of Linux on the desktop has been a controversial topic; for example in 2007 [[Con Kolivas]] accused the Linux community of favoring performance on servers. He quit Linux kernel development because he was frustrated with this lack of focus on the desktop, and then gave a "tell all" interview on the topic.<ref>{{cite web|title=Linux: why I quit|url=http://apcmag.com/node/6735/|accessdate=2008-01-18|date=2007-07-24|work=APC Magazine|publisher=ACP Magazines}}</ref> Since then a significant amount of development has been undertaken in an effort to improve the desktop experience. Projects such as [[Upstart]] aim for a faster boot time.<ref>{{cite web|title=Performance of Java on Ubuntu vs Windows|url=http://www.phoronix.com/scan.php?page=article&item=java_vm_performance&num=1}}</ref>
Many popular applications are available for a wide variety of operating systems. For example [[Mozilla Firefox]], [[OpenOffice.org]] and [[Blender (software)|Blender]] have downloadable versions for all major operating systems. Furthermore, some applications were initially developed for Linux, such as [[Pidgin (software)|Pidgin]], and [[GIMP]], and were ported to other operating systems including [[Microsoft Windows|Windows]] and [[Mac OS X]] due to their popularity. In addition, a growing number of proprietary desktop applications are also supported on Linux;<ref>{{cite web | url = http://www.iist.unu.edu/globaldesktop/ | title = The Global Desktop Project, Building Technology and Communities|accessdate = 2006-05-07 }}</ref> see [[List of proprietary software for Linux]]. In the field of animation and visual effects, most high end software, such as [[Maya (software)|AutoDesk Maya]], Softimage XSI and [[Shake (software)|Apple Shake]], is available for Linux, Windows and/or Mac OS X. There are also [[Linux gaming#Commercial games|several companies]] that have ported their own or other companies' games to Linux.
Many types of applications available for Microsoft Windows and Mac OS X are also available for Linux. Commonly, either a [[free software]] application will exist which does the functions of an application found on another operating system, or that application will have a version that works on Linux, such as with [[Skype]] and some [[Linux gaming#Commercial games|video games]]. {{Citation needed|date=May 2011}} Furthermore, the [[Wine (software)|Wine]] project provides a Windows compatibility layer to run unmodified Windows applications on Linux. [[CrossOver]] is a proprietary solution based on the open source [[Wine (software)|Wine]] project that supports running Windows versions of [[Microsoft Office]], [[Intuit]] applications such as [[Quicken]] and [[QuickBooks]], [[Adobe Photoshop]] versions through CS2, and many popular games such as ''[[World of Warcraft]]'' and ''[[Team Fortress 2]]''. In other cases, where there is no Linux port of some software in areas such as [[desktop publishing]]<ref>{{cite web|url=http://www.freeos.com/articles/2540/ |title=Microsoft Office for Linux? |accessdate=2008-02-03 |last=Advani |first=Prakash |date=2000-10-27 |work=FreeOS |publisher=FreeOS Technologies (I) Pvt. Ltd. }}</ref> and [[professional audio]],<ref>{{cite web|url=http://arstechnica.com/guides/tweaks/linux-audio.ars |title=Editing audio in Linux |accessdate=2008-02-03 |last=Smith-Heisters |first=Ian |date=2005-10-11 |work=Ars Technica |publisher=Ars Technica, LLC }}</ref><ref>{{cite web|url=http://www.keyboardmag.com/article/linux-its-not/apr-07/27458 |title=Linux: It's Not Just For Computer Geeks Anymore |accessdate=2008-02-03 |last=Lumma |first=Carl |date = April 2007|work=Keyboard Magazine |publisher=New Bay Media, LLC. }}</ref><ref>{{cite web|url=http://www.soundonsound.com/sos/feb04/articles/mirrorimage.htm |title=Using Linux For Recording & Mastering |accessdate=2008-02-03 |last=James |first=Daniel |date = February 2004|work=Sound On Sound |publisher=SOS Publications Group }}</ref> there is equivalent software available on Linux.
The collaborative nature of free software development allows distributed teams to perform [[language localisation|language localization]] of some Linux distributions for use in locales where localizing proprietary systems would not be cost-effective. For example the [[Sinhalese language]] version of the [[Knoppix]] distribution was available significantly before [[Microsoft Windows XP]] was translated to Sinhalese.{{Citation needed|date=April 2009}} In this case the [[Lanka Linux User Group]] played a major part in developing the localized system by combining the knowledge of university professors, [[linguist]]s, and local developers.
Installing, updating and removing software in Linux is typically done through the use of package managers such as the [[Synaptic Package Manager]], [[PackageKit]], and [[Yellow dog Updater, Modified|Yum Extender]]. While most major Linux distributions have extensive repositories, often containing tens of thousands of packages, not all the software that can run on Linux is available from the official repositories. Alternatively, users can install packages from unofficial repositories, download pre-compiled packages directly from websites, or compile the source code by themselves. All these methods come with different degrees of difficulty, compiling the source code is in general considered a challenging process for new Linux users, but it's hardly needed in modern distributions and is not a method specific to Linux.
<center><gallery>
File:GNOME Shell.png|[[GNOME Shell]]
File:Kde42default.png|[[KDE Plasma Desktop]]
File:Ubuntu 11.04 Installation SS.png|[[Unity (desktop environment)|Unity]]
File:Xfce-4.4.png|[[Xfce]]
File:LXDE desktop full.png|[[LXDE]]
</gallery></center>
===Servers, mainframes and supercomputers===
{{multiple image
|direction=horizontal|width=200
|image2=Server Linux.jpg
|caption2=Servers designed for Linux
|image1=JaguarXT5.jpg
|caption1=The [[Oak Ridge National Laboratory]]'s [[National Center for Computational Sciences#Jaguar|Jaguar supercomputer]], until recently the world's fastest supercomputer. It uses the [[Unicos#Variants|Cray Linux Environment]] as its operating system.<ref name="CrayJag">{{cite web|url = http://www.top500.org/system/10184|title = Jaguar|accessdate = 2009-11-18|last = TOP500.Org|authorlink = |year = 2009}}</ref><ref name="NCCSJag">{{cite web|url = http://www.nccs.gov/computing-resources/jaguar/|title = Jaguar|accessdate = 2009-11-18|last = National Center for Computational Sciences|authorlink = |year = 2009|month = October}}</ref>
}}
[[Linux distributions]] have long been used as [[server (computing)|server]] operating systems, and have risen to prominence in that area; [[Netcraft]] reported in September 2006 that eight of the ten most reliable internet hosting companies ran Linux distributions on their [[web server]]s.<ref>{{cite web | title = Rackspace Most Reliable Hoster in September | url = http://news.netcraft.com/archives/2006/10/07/rackspace_most_reliable_hoster_in_september.html | publisher = Netcraft | date = 7 October 2006 | accessdate = 2006-11-01}}</ref> Since June 2008, Linux distributions represented five of the top ten, [[FreeBSD]] three of ten, and [[Microsoft]] two of ten;<ref>{{cite web | title = Aplus.Net is the Most Reliable Hosting Company Site in June 2008 | url = http://news.netcraft.com/archives/2008/07/07/aplusnet_is_the_most_reliable_hosting_company_site_in_june_2008.html | publisher = Netcraft | date = 7 July 2008 | accessdate = 2008-07-28}}</ref> since February 2010, Linux distributions represented six of the top ten, [[FreeBSD]] two of ten, and [[Microsoft]] one of ten.<ref>{{cite web | title = Most Reliable Hosting Company Sites in February 2010 | url = http://news.netcraft.com/archives/2010/03/01/most_reliable_hosting_company_sites_in_february_2010.html | publisher = Netcraft | date = 1 March 2010 | accessdate = 2010-03-23}}</ref>
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