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'''Linux''' (pronunciation: {{IPAEng|ˈlɪnʊks}}) is a [[Unix-like]] computer [[operating system]]. Linux is one of the most prominent examples of [[free software]] and [[open source]] development; typically all underlying [[source code]] can be freely modified, used, and redistributed by anyone.<ref>{{ cite web | title = Linux Online ─ About the Linux Operating System | url = http://www.linux.org/info/index.html | publisher = Linux.org | accessdate = 2007-07-06 }}</ref>
'''Linux''' (pronunciation: {{IPAEng|ˈlɪnəks}}) is a [[Unix-like]] computer [[operating system]]. Linux is one of the most prominent examples of [[free software]] and [[open source]] development; typically all underlying [[source code]] can be freely modified, used, and redistributed by anyone.<ref>{{ cite web | title = Linux Online ─ About the Linux Operating System | url = http://www.linux.org/info/index.html | publisher = Linux.org | accessdate = 2007-07-06 }}</ref>


The [[Linux kernel]] was first released to the public on [[17 September]] [[1991]], for the [[x86 architecture|Intel x86]] PC architecture. The kernel was augmented with [[system utility|system utilities]] and [[library (computer science)|libraries]] from the [[GNU]] project to create a usable operating system, which [[GNU/Linux naming controversy|led to an alternative term]], '''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 | date = 2004 | accessdate = 2007-01-18 | first = Alex | last = Weeks }}</ref> Linux is packaged for different uses in [[Linux distribution]]s, which contain the sometimes modified kernel along with a variety of other software packages tailored to different requirements.
The [[Linux kernel]] was first released to the public on [[17 September]] [[1991]], for the [[x86 architecture|Intel x86]] PC architecture. The kernel was augmented with [[system utility|system utilities]] and [[library (computer science)|libraries]] from the [[GNU]] project to create a usable operating system, which [[GNU/Linux naming controversy|led to an alternative term]], '''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 | date = 2004 | accessdate = 2007-01-18 | first = Alex | last = Weeks }}</ref> Linux is packaged for different uses in [[Linux distribution]]s, which contain the sometimes modified kernel along with a variety of other software packages tailored to different requirements.
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[[Image:Richard Matthew Stallman.jpeg|thumb|left|[[Richard Stallman]], founder of the [[GNU project]] ]]
[[Image:Richard Matthew Stallman.jpeg|thumb|left|[[Richard Stallman]], founder of the [[GNU project]] ]]


The [[GNU Project]], started in 1984, had the goal of creating a "''complete Unix-compatible software system''"<ref name="gnu_announce">[http://www.gnu.org/gnu/init
The [[GNU Project]], started in 1984, had the goal of creating a "''complete Unix-compatible software system''"<ref name="gnu_announce">[http://www.gnu.org/gnu/initial-announcement.html About the GNU Project - Initial Announcement]</ref> made entirely of [[free software]]. In 1985, [[Richard Stallman]] created the [[Free Software Foundation]] and developed the [[GNU General Public License]] (GNU GPL). Many of the programs required in an OS (such as libraries, [[compiler]]s, [[text editor]]s, a [[Unix shell]], and a windowing system) were completed by the early 1990s, although low level elements such as [[device driver]]s, [[daemon (computer software)|daemon]]s, and the [[Kernel (computer science)|kernel]] were stalled and incomplete.<ref name="gnu history">[http://www.gnu.org/gnu/gnu-history.html Overview of the GNU System]</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://people.fluidsignal.com/~luferbu/misc/Linus_vs_Tanenbaum.html | title = Linus vs. Tanenbaum debate }}</ref>

=== MINIX ===
[[Image:Linus Torvalds.jpeg|thumb|right|[[Linus Torvalds]], creator of the [[Linux kernel]]]]

[[MINIX]], a Unix-like system intended for academic use, was released by [[Andrew S. Tanenbaum]] in 1987. While source code for the system was available, modification and redistribution were restricted. In addition, MINIX's [[16-bit]] design was not well adapted to the [[32-bit]] design of the increasingly cheap and popular [[Intel 386]] architecture for personal computers.

In 1991, [[Linus Torvalds]] began to work on a non-commercial replacement for MINIX while he was attending the [[University of Helsinki]].<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> This eventually became the [[Linux kernel]].

Linux was dependent on the MINIX [[userspace]] at first. With code from the GNU system freely available, it was advantageous if this could be used with the fledgling OS. 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 kernel compatible with the components from the GNU Project, 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 as of the first of February. If you do not know the gist of the GNU copyright ─ read it. }}</ref> Linux and GNU 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 ===
Today Linux is used in numerous domains, from [[embedded systems]]<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> to [[supercomputers]],<ref>{{cite web| 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}}</ref> and has secured a place in [[server (computing)|server]] installations with 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> 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.

== Development ==
{{main|Linux distribution}}

[[Image:Unix history.en.svg|thumb|220px|A graphical history of [[Unix]] systems. Linux is a Unix-type system but its source code does not descend from the original Unix.]]

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 the best-known and most widely used. Some [[free software license|free]] and [[open source license|open source]] software licences 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 used for the Linux kernel and many of the components from the [[GNU project]].

As an operating system [[underdog (competition)|underdog]] competing with mainstream operating systems, Linux cannot rely on a [[monopoly]] advantage; in order for Linux to be convenient for users, Linux aims 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> [[ISO]], and [[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. However, given that the software licenses explicitly permit redistribution, this 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 Linux-based software, and facilitates installation of a Linux operating system. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. They include system software and [[application software]] in the form of ''packages'', and distribution-specific software for initial system installation and configuration as well as later package upgrades and installs. A distribution is responsible for the default configuration of installed Linux systems, system security, and more generally integration of the different software packages into a coherent whole.

=== Community ===
[[Image:Bash screenshot.png|thumb|A command line session using [[bash]]]]

Linux 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]].

In many cities and regions, local associations known as [[Linux Users Group]]s (LUGs) seek to promote Linux and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. There are also many [[Internet]] communities that seek to provide support to Linux users and developers. Most distributions and 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 [[Gentoo Linux|Gentoo]] forums. 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. [[Linux Weekly News]] is a weekly digest of Linux-related news; the [[Linux Journal]] is an online magazine of Linux articles published monthly; [[Slashdot]] is a technology-related news website with many stories on Linux and open source software; [[Groklaw]] has written in depth about Linux-related legal proceedings and there are many articles relevant to the Linux kernel and its relationship with the [[GNU]] on [[GNU Project|the project's]] website.

There are also many magazines with a Linux focus. One of them is [[Linux Format (magazine)|Linux Format]]. This magazine has Linux-related tips, news, tricks and DVDs or CDs with Linux software, and often one or two Linux distributions.

Although Linux is generally available free of charge, several large corporations have established business models that involve selling, supporting, and contributing to Linux and free software. These include [[Dell]], [[IBM]], [[Hewlett-Packard|HP]], [[Sun Microsystems]], [[Novell]], and [[Red Hat]]. The free software licenses on which Linux is based explicitly accommodate and encourage commercialization; the relationship between Linux as a whole and individual vendors may be seen as [[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.

=== Programming on Linux ===
Most 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]]. Amongst others, GCC provides compilers for [[C (programming language)|C]], [[C++]], [[Java (programming language)|Java]], [[Ada (programming language)|Ada]] and [[Fortran]]. The Linux kernel itself is written to be compiled with GCC. [[Proprietary software|Proprietary]] solutions compilers for Linux include the [[Intel C++ Compiler]].

Most also include support for [[Perl]], [[Ruby programming language|Ruby]], [[Python programming language|Python]] and other [[Dynamic programming language|dynamic languages]]. Examples of languages that are less common, but still well-supported, are [[C Sharp (programming language)|C#]] via the [[Mono (software)|Mono]] project, 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]]. The two main frameworks for developing graphical applications are those of [[GNOME]] and [[KDE]]. 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]], [[Eclipse (computing)|Eclipse]], [[KDevelop]], [[MonoDevelop]], [[NetBeans]], and [[Omnis Studio]] while the traditional 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>

== Design ==
<!-- stub section to give an overview of "what Linux is": a Unix-like general-purpose OS with a modular design -->

Linux is a modular [[Unix-like]] operating system. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Linux uses a [[monolithic kernel]], the [[Linux kernel]], which handles process control, networking, and [[peripheral]] and [[file system]] access. [[Device drivers]] are integrated directly with the kernel.

Much of Linux's higher-level functionality is provided by separate projects which interface with the kernel. The GNU [[Userland (computing)|userland]] is an important part of most Linux systems, providing the [[shell (computing)|shell]] and [[Unix tool]]s which carry out many basic operating system tasks. On top these tools form a Linux system with a [[graphical user interface]] that can be used, usually running in the [[X Window System]].

{{section-stub}}

=== User interface ===
{{see also|User interface}}

Linux can be controlled by one or more of a text-based [[command line interface]] (CLI), [[graphical user interface]] (GUI) (usually the default for desktop), through controls on the device itself (common on embedded machines).

On desktop machines, [[KDE]], [[GNOME]] and [[Xfce]] are the most popular user interfaces.<ref>{{ cite web | title = Debian popularity-contest program information | url = http://times.debian.net/1092-30000-popcon-submissions }}</ref>, though a variety of other user interfaces exist. Most popular user interfaces run on top of the [[X Window System]] (X), which provides [[network transparency]], enabling graphical apps running on one machine to be displayed and controlled from another.

Other GUIs include [[X window manager]]s such as [[FVWM]], [[Enlightenment (window manager)|Enlightenment]] and [[Window Maker]]. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the [[X window system]].

Linux systems usually provide a [[CLI]] of some sort through a [[Shell (computing)|shell]], which is the traditional way of interacting with Unix systems. Linux distributions specialized for servers may use the CLI as their only interface. “Headless systems” run without even a monitor can be controlled by command line via a protocol such as [[Secure Shell|SSH]] or [[telnet]].

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]]. Graphical [[terminal emulator]] programs are often used to access the CLI from a Linux desktop.

== 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. While the Linux kernel was originally designed only for [[Intel 80386]] [[microprocessor]]s, it now runs on a more diverse range of [[computer architecture]]s than any other operating system—from the hand-held [[ARM architecture|ARM]]-based [[iPAQ]] to the [[mainframe computer|mainframe]] [[IBM]] [[System z9]], in devices ranging from [[supercomputer]]s to [[mobile phone]]s.<ref>{{ cite web| url = http://www.freeos.com/articles/4737/ | title = If I could re-write Linux | first = Prakash | last = Advani | date = [[February 8]] [[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 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, [[Personal digital assistant|PDA]]s, [[Video game console]]s, [[Digital audio player|portable music players]], and [[Mobile phone]]s.

=== Desktop ===
{{main|Desktop Linux}}
[[Image:Kde35.png|thumb|right|250px|KDE 3.5, showing the [[Kontact]] personal information manager and [[Konqueror]] file manager, web browser, and file viewer.]]

Although in specialized application domains such as [[desktop publishing]] and [[professional audio]] there may be a lack of high quality software, users migrating from Mac OS X and Windows can find equivalent applications for most tasks.<ref>{{ cite web | title = The table of equivalents/replacements/analogs of Windows software in Linux | url = http://www.linuxrsp.ru/win-lin-soft/table-eng.html }}</ref>

Many [[free software]] titles that are popular on Windows are also available, such as [[Pidgin (software)|Pidgin]], [[Mozilla Firefox]], [[Openoffice.org]], and [[GIMP]], amongst others. A growing amount of proprietary desktop software is also supported under 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> examples being [[Adobe Flash Player]], [[Adobe Acrobat|Acrobat Reader]], [[Matlab]], [[Nero Burning ROM]], [[Opera (Internet suite)|Opera]], [[RealPlayer]], and [[Skype]]. In the field of animation and visual effects, most high end software, such as AutoDesk Maya, Softimage XSI and Apple Shake are available both for Linux, Windows and/or MacOS X. Additionally, [[CrossOver]] is a proprietary solution based on the open source [[Wine (software)|Wine]] project that supports running older, superseded Windows versions of [[Microsoft Office]] and [[Adobe Photoshop]]. ([[Microsoft Office 2007]] and Adobe Photoshop CS are known not to work,<ref> {{cite web|url=http://www.codeweavers.com/compatibility/browse/group/?app_parent=1911 |title=Microsoft Office 2007 |accessdate=2008-01-05 |date=2007-11-25 |work=CodeWeavers |publisher=CodeWeavers Inc. }}</ref><ref> {{cite web|url=http://www.codeweavers.com/compatibility/browse/name/?app_id=385 |title=Photoshop CS |accessdate=2008-01-05 |date=2005-08-01 |work=CodeWeavers |publisher=CodeWeavers Inc. }}</ref>
while Adobe Photoshop CS2 and CS3 are untested and unsupported.<ref> {{cite web|url=http://www.codeweavers.com/compatibility/browse/name/?app_id=1288 |title=Photoshop CS 2 |accessdate=2008-01-05 |date=2007-01-25 |work=CodeWeavers |publisher=CodeWeavers Inc. }}</ref><ref> {{cite web|url=http://www.codeweavers.com/compatibility/browse/name/?app_id=3175 |title=Photoshop CS 3 |accessdate=2008-01-05 |date=2007-07-11 |work=CodeWeavers |publisher=CodeWeavers Inc. }}</ref>)

Linux's open nature offers the ability for distributed teams to [[L10n|localize]] Linux distributions for use in locales where doing so to proprietary systems would not be cost-effective. For example, the [[Sinhalese language]] version of the [[Knoppix]] distribution was available for a long time before the initiation of translation of [[Microsoft Windows XP]] to Sinhalese. 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.

{{see also|Linux gaming}}

=== Servers and supercomputers ===
Historically, Linux has mainly been used as a [[Server (computing)|server]] operating system, and has risen to prominence in that area; [[Netcraft]] reported in September 2006 that eight of the ten most reliable internet hosting companies run Linux 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 = [[October 7]] [[2006]] | accessdate = 2006-11-01}}</ref> This is due to its relative stability and long uptime, and the fact that desktop software with a graphical user interface is often unneeded. Enterprise and non-enterprise Linux distributions may be found running on servers. Linux is the cornerstone of the [[LAMP (software bundle)|LAMP]] server-software combination (Linux, [[Apache HTTP Server|Apache]], [[MySQL]], [[Perl]]/[[PHP]]/[[Python (programming language)|Python]]) which has achieved popularity among developers, and which is one of the more common platforms for website hosting.

Linux is commonly used as an operating system for [[supercomputer]]s. As of [[November 2007]], out of the top 500 systems, 426 (85.2%) run Linux.<ref>http://www.top500.org/stats/list/30/osfam</ref>

=== Embedded devices ===
{{main|embedded Linux}}
Due to its low cost and ability to be easily modified, an [[embedded Linux]] is often used in [[embedded systems]]. Linux has become a major competitor to the proprietary [[Symbian OS]] found in many mobile phones — 16.7% of [[smartphone]]s sold worldwide during 2006 were using Linux<ref>{{ cite web | url = http://www.informationweek.com/showArticle.jhtml?articleID=197000995 | title = The Palm OS Clings To Life }}</ref> — and it is an alternative to the dominant [[Windows CE]] and [[Palm OS]] operating systems on [[handheld device]]s. The popular [[TiVo]] digital video recorder uses a customized version of Linux.<ref>{{cite web | url = http://www.tivo.com/linux/linux.asp | title = TiVo ─ GNU/Linux Source Code | accessdate = 2006-12-12 |archiveurl=http://web.archive.org/web/20070519150730/http://www.tivo.com/linux/linux.asp |archivedate=2007-05-19}}</ref> Several network [[firewall]] and [[router]] standalone products, including several from [[Linksys]], use Linux internally, using its advanced firewall and routing capabilities. The [[Korg OASYS]] and the [[Yamaha Motif|Yamaha Motif XS]] [[music workstation]]s also run Linux.<ref>{{cite web |url=http://www.mvista.com/downloads/Case_study_MontaVista_Linux_and_Yamaha.pdf |title=Case Study: How MontaVista Linux helped Yamaha developers make a great product greater |accessdate=2007-08-26}}</ref>

=== Market share and uptake ===
[[Image:Gnome-2.16-screenshot.png|thumb|250px|GNOME 2.16, showing the [[Nautilus (file manager)|Nautilus]] file manager and the [[gedit]] text editor.]]
{{Main|Linux adoption}}

Many quantitative studies of open source software focus on topics including market share and reliability, with numerous studies specifically examining Linux.<ref>{{ cite web | first = David A | last = Wheeler | url = http://www.dwheeler.com/oss_fs_why.html | title = Why Open Source Software/Free Software (OSS/FS)? Look at the Numbers! | accessdate = 2006-04-01 }}</ref> The Linux market is growing rapidly, and the revenue of servers, desktops, and packaged software running Linux is expected to exceed $35.7 billion by 2008.<ref>{{ cite web | url = http://www.techweb.com/wire/showArticle.jhtml?articleID=55800522 | title = Linux To Ring Up $35 Billion By 2008 | accessdate = 2006-04-01 }}</ref>

[[International Data Corporation|IDC]]'s report for Q1 2007 says that Linux now holds 12.7% of the overall server market.<ref name="Linux-watch.com IDC's Q1 2007 report">[http://www.linux-watch.com/news/NS5369154346.html Linux-watch.com ─ IDC Q1 2007 report]</ref> This estimate was based on the number of Linux servers sold by various companies.

Desktop adoption of Linux is approximately 1%. In comparison, [[List of Microsoft operating systems|Microsoft operating systems]] hold more than 90%.
<ref>{{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/article2/0,1895,2168426,00.asp | work =eWEEK | pages = | accessdate = 2007-11-19 | language = }}</ref>
<ref>{{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>{{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> {{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>{{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> {{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> {{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>

The frictional cost of switching operating systems and lack of support for certain hardware and application programs designed for [[Microsoft Windows]] have been two factors that have inhibited adoption. Proponents and analysts attribute the relative success of Linux to its security, reliability,<ref>{{ cite web | url = http://www-306.ibm.com/software/info/features/feb152005/ | title = Why customers are flocking to Linux }}</ref> low cost, and freedom from [[vendor lock-in]].<ref>{{cite web | url = http://www.ca.com/za/news/2005/20051010_linux.htm| title = The rise and rise of Linux }}</ref>

The [[XO-1 (laptop)|XO laptop]] project of One Laptop Per Child is creating a new and potentially much larger Linux community, planned to reach [http://www.laptop.org/en/vision/mission/index.shtml several hundred million schoolchildren] and their families and communities in developing countries. [http://wiki.laptop.org/go/countries Six countries] have ordered a million or more units each for delivery in 2007 to distribute to schoolchildren at no charge. [[Google]], [[Red Hat]], and [[eBay]] are major supporters of the project.{{Fact|date=November 2007}}

{{see also|Usage share of desktop operating systems}}

== Copyright and naming ==
The Linux kernel and most GNU software are [[software license|license]]d under the [[GNU General Public License]] (GPL), version 2. The GPL requires that anyone who distributes the Linux kernel must make the source code (and any modifications) available to the recipient under the same terms. In 1997, Linus Torvalds stated, “Making Linux GPL'd was definitely the best thing I ever did.”<ref>{{cite web | url = http://kde.sw.com.sg/food/linus.html | title = Linus Torvalds interview | accessdate = 2007-09-13 |archiveurl=http://web.archive.org/web/20070311190841/http://kde.sw.com.sg/food/linus.html |archivedate=2007-03-11}}</ref> Other key components of a Linux system may use other licenses; many libraries use the [[GNU Lesser General Public License]] (LGPL), a more permissive variant of the GPL, and the [[X Window System]] uses the [[MIT License]].

Torvalds has publicly stated that he would not move the Linux kernel to version 3 of the GPL, released in mid-2007, specifically citing some provisions in the new license which prohibit the use of the software in [[digital rights management]].<ref>{{cite web | url=http://lkml.org/lkml/2006/1/25/273 | title=Re: GPL V3 and Linux ─ Dead Copyright Holders | author=Torvalds, Linus | date=2006-01-26 | publisher=[[Linux Kernel Mailing List]]}}</ref><ref>{{cite web | url=http://lkml.org/lkml/2006/9/25/161 | title=Re: GPLv3 Position Statement | author=Torvalds, Linus | date=2006-09-25 | publisher=[[Linux Kernel Mailing List]]}}</ref>

A 2001 study of [[Red Hat Linux]] 7.1 found that this distribution contained 30 million [[source lines of code]]. Using the [[COCOMO|Constructive Cost Model]], the study estimated that this distribution required about eight thousand man-years of development time. According to the study, if all this software had been developed by conventional [[proprietary software|proprietary]] means, it would have cost about 1.08 billion dollars (year 2000 U.S. dollars) to develop in the United States.<ref name = "estimating_size">{{ cite web | first = David A | last = Wheeler | date = 2002-07-29 | url = http://www.dwheeler.com/sloc/redhat71-v1/redhat71sloc.html | title = More Than a Gigabuck: Estimating GNU/Linux's Size | accessdate = 2006-05-11 }}</ref>

Most of the code (71%) was written in the [[C (programming language)|C]] [[computer programming|programming]] [[programming language|language]], but many other languages were used, including [[C++]], [[assembly language]], [[Perl]], [[Fortran]], [[Python (programming language)|Python]] and various [[shell script]]ing languages. Slightly over half of all lines of code were licensed under the GPL. The Linux kernel itself was 2.4 million lines of code, or 8% of the total.<ref name = "estimating_size"/>

In a later study, the same analysis was performed for Debian GNU/Linux version 4.0.<ref>{{ cite web | first = Juan José | last = Amor | coauthors = et al | date = [[17 June]] [[2007]] | url = https://penta.debconf.org/~joerg/attachments/33-measuring_etch_slides.pdf | title = Measuring Etch: the size of Debian 4.0 | accessdate = 2007-09-16 }}</ref> This distribution contained over 283 million source lines of code, and the study estimated that it would have cost 5.4 billion Euros to develop by conventional means.

In the United States, the name ''Linux'' is a [[trademark]] registered to Linus Torvalds.<ref>{{ cite web | url = http://assignments.uspto.gov/assignments/q?db=tm&rno=1916230 | title = U.S. Reg No: 1916230 | publisher = United States Patent and Trademark Office | accessdate = 2006-04-01 }}</ref> Initially, nobody registered it, but on [[August 15]] [[1994]], William R. Della Croce, Jr. filed for the trademark ''Linux'', and then demanded royalties from Linux distributors. In 1996, Torvalds and some affected organizations sued him to have the trademark assigned to Torvalds, and in 1997 the case was settled.<ref>{{cite web | url = http://www.linuxjournal.com/article/9065 | title = Linux Timeline | publisher = Linux Journal | date = [[31 May]] [[2006]] }}</ref> The licensing of the trademark has since been handled by the [[Linux Mark Institute]]. Torvalds has stated that he only trademarked the name to prevent someone else from using it, but was bound in 2005 by [[United States trademark law]] to take active measures to enforce the trademark. As a result, the LMI sent out a number of letters to distribution vendors requesting that a fee be paid for the use of the name, and a number of companies have complied.<ref>{{ cite web | url = http://www.infoworld.com/article/05/09/05/36OPopenent_1.html | title = Linus gets tough on Linux trademark | accessdate = 2006-09-04 | date = 2005-09-05 }}</ref>

{{see also|SCO-Linux controversies}}

=== GNU/Linux ===
{{main|GNU/Linux naming controversy}}

The [[Free Software Foundation]] views Linux distributions which use GNU software as “[[GNU variants]]” and they ask that such operating systems be referred to as ''GNU/Linux'' or ''a Linux-based GNU system''.<ref>{{cite web | title = Linux and the GNU Project | url = http://www.gnu.org/gnu/linux-and-gnu.html | first = Richard | last = Stallman | authorlink = Richard Stallman | date = 2007-03-03 | accessdate = 2007-03-12 | publisher = Free Software Foundation }}</ref> However, the media and population at large refers to this family of operating systems simply as ''Linux''. While some distributors make a point of using the aggregate form, most notably [[Debian]] with the ''[[Debian GNU/Linux]]'' distribution, the term's use outside of the enthusiast community is limited. The distinction between the Linux kernel and distributions based on it plus the GNU system is a source of confusion to many newcomers, and the naming remains controversial.

== See also ==
{{portal|Free software|Free Software Portal Logo.svg}}

* [[List of Linux distributions]]
* [[Comparison of Linux distributions]]
* [[Comparison of Windows and Linux]]
* [[Comparison of open source and closed source]]
* [[The Cathedral and the Bazaar]]
* [[:Category:Linux software|Linux software]]
* [[Plan 9 from Bell Labs]] - free successor of AT&T Unix
* [[Linux Documentation Project]] - Source of detailed documentation and How To manuals

== References ==
{{reflist|3}}

== External links ==
{{Sisterlinks|Linux}}
* [http://www.kernel.org/ Linux kernel website and archives]
* [http://www.linuxmark.org/ The Linux Mark Institute] (manages the Linux trade mark)
* [http://www.linux-foundation.org/ The Linux Foundation]
* [http://www.gnu.org/ GNU Project website]
* [http://www.google.com/options/specialsearches.html Google Linux Search].
* [http://linuxzoo.net/ linuxzoo] Online Linux system with root access.
* [http://www.makelinux.net/reference Linux Technology Reference]
* [http://www.tldp.org/ The Linux Documentation Project]

{{unix-like}}
{{linux-distro}}

[[Category:Computing platforms]]
[[Category:Linux|*]]

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Revision as of 13:19, 11 January 2008

Template:Two other uses

Linux
Tux, the penguin, mascot of Linux
Tux, the penguin, mascot of the Linux kernel
OS familyUnix-like
Working stateCurrent
Latest release2.6.23.13 (Linux kernel) / 9 January 2008
Kernel typeMonolithic kernel
LicenseGNU General Public License and others
Official websitekernel.org

Linux (pronunciation: /ˈlɪnəks/) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; typically all underlying source code can be freely modified, used, and redistributed by anyone.[1]

The Linux kernel was first released to the public on 17 September 1991, for the Intel x86 PC architecture. The kernel was augmented with system utilities and libraries from the GNU project to create a usable operating system, which led to an alternative term, GNU/Linux.[2] Linux is packaged for different uses in Linux distributions, which contain the sometimes modified kernel along with a variety of other software packages tailored to different requirements.

Predominantly known for its use in servers, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, supercomputers,[3] video game systems, such as PlayStation 2, 3, several arcade games, and embedded devices, such as mobile phones and routers.

In 1992, Linus Torvalds explained that he pronounces Linux as /ˈlɪnʊks/,[4] though other variations are common.

History

See also: History of Linux

The Unix operating system was conceived and implemented in the 1960s and first released in 1970. Its wide availability and portability meant that it was widely adopted, copied and modified by academic institutions and businesses, with its design being influential on authors of other systems.

File:Richard Matthew Stallman.jpeg
Richard Stallman, founder of the GNU project

The GNU Project, started in 1984, had the goal of creating a "complete Unix-compatible software system"<ref name="gnu_announce">[http://www.gnu.org/gnu/init

  1. ^ "Linux Online ─ About the Linux Operating System". Linux.org. Retrieved 2007-07-06.
  2. ^ Weeks, Alex (2004). "1.1". Linux System Administrator's Guide (version 0.9 ed.). Retrieved 2007-01-18.
  3. ^ Lyons, Daniel. "Linux rules supercomputers". Retrieved 2007-02-22.
  4. ^ "Re: How to pronounce "Linux"?". 23 April 1992. 1992Apr23.123216.22024@klaava.Helsinki.FI. {{cite newsgroup}}: |access-date= requires |url= (help); Check date values in: |date= (help); Unknown parameter |newsgroups= ignored (help) Torvalds has made available an audio sample which indicates his own pronunciation, in English (/ˈlɪnʊks/) ─ "How to pronounce Linux?". Retrieved 2006-12-17. ─ and Swedish (/ˈlɪːnɤks/) ─ "Linus pronouncing Linux in English and Swedish". Retrieved 2007-01-20.
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