Linux

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Linux

Tux the penguin, the mascot of the Linux kernel
OS family:	Unix-like
Latest stable release:	2.6.20.4 (Linux kernel) / March 23, 2007
Kernel type:	Modular monolithic kernel
License:	GNU General Public License
Working state:	Current

Linux (IPA pronunciation: /ˈlɪnʊks/) is a Unix-like computer operating system family. Linux is one of the most prominent examples of free software and of open source development; its underlying source code is available for anyone to use, modify, and redistribute freely.^[1]

The first Linux systems were completed in 1992 by combining system utilities and libraries from the GNU project with the Linux kernel, which led to the coining of the term GNU/Linux.^[2] From the late 1990s onward Linux gained the support of corporations such as IBM,^[3] Sun Microsystems,^[4] Hewlett-Packard,^[5] and Novell.^[6]

Predominantly known for its use in servers, Linux is used as an operating system for a wider variety of computer hardware than any other operating system, including desktop computers, supercomputers,^[7] mainframes, and embedded devices such as cellphones. Linux is packaged for different uses in Linux distributions, which contain the kernel along with a variety of other software packages tailored to requirements.

Contents 1 History 1.1 Development milestones 1.2 Present day 1.3 Adoption 1.4 Naming 2 Copyright and Trademark 2.1 Source code analysis 2.2 Trademark 3 Philosophy 3.1 Interoperability 3.2 Portability 3.3 Community 4 Distributions 5 Interface 5.1 Command line interface 5.2 X window managers 5.3 Desktop environments 6 Applications 6.1 Desktop 6.1.1 Games 6.1.2 Comparison with Windows 6.2 Servers, supercomputers and embedded devices 6.3 Software development 7 References 8 See also 9 External links

[edit] History

On 27 September 1983, Richard Stallman announced the GNU Project, with the goal of creating a UNIX-like, POSIX-compatible operating system composed entirely of free software.^[8] Development began in 1984, and a year later he created the Free Software Foundation and wrote the first draft of the GNU General Public License (GPLv1). By the early 1990s, the project had produced or collected many necessary operating system components, including libraries, compilers, text editors, and a Unix shell, and the mid-level portions of the OS were almost complete. The upper level could be supplied by the X Window System, but the lower level which consisted of a kernel, device drivers, and daemons was still incomplete. In 1990 the GNU project began developing the Hurd kernel which was based on the Mach microkernel, but development proved difficult and proceeded slowly.^[9]

In 1991, Linus Torvalds began to work on the Linux kernel while he was attending the University of Helsinki.^[10] Torvalds originally created the Linux kernel as a non-commercial replacement for the Minix kernel;^[11] he later changed his original license to the GPLv2, which differed primarily in that it also allowed for commercial redistribution.^[12] Although dependent on the Minix userspace at first, work from both Linux kernel developers and the GNU project allowed Linux to work with GNU components. Thus Linux filled the last major gap in running a complete, fully functional free operating system.^[9]

In 2004, Ken Brown of the Alexis de Tocqueville Institution cast doubt on Linus' authorship of Linux, which was rebutted^[13] by Minix's author, Andrew S. Tanenbaum.

[edit] Development milestones

This foundation formed the basis for an operating system which has since been completed by the efforts of numerous members of the free and open source software community. Significant milestones include:

• The launch of the KDE desktop environment by Matthias Ettrich in October 1996 followed by the comparable GNOME alternative by Miguel de Icaza in August 1997, both based on the X11 windowing system developed at MIT. GNOME and KDE were the tip of the Linux operating system iceberg that was now in direct contact with end users.
• The release of the Netscape browser's source code on March 31, 1998, which kicked off the Mozilla project that would eventually give birth to the popular Mozilla Firefox browser.

• The release of StarOffice by Sun Microsystems which in June 2000 became the base for the free software OpenOffice.org office suite ^[14], a major event in the open source office world. See also: list of free software.
• The growth of commercial interest in Linux is similarly marked by notable events: the launch in February 1998 of the Open Source Initiative; the announcement in July 1998 by Oracle Corporation that it would port its well-known database software to Linux and provide support for it; the IPOs of Red Hat on November 11, 1999 and VA Linux the following month which would create a speculative bubble; the wide-scale support of technology giant IBM that would spend millions of dollars on Linux, employing in 2005 close to 300 developers of the Linux kernel, and would organize starting in 2003 the legal defense for the SCO vs. Linux controversy against the attacks of the SCO Group that claimed copyright over the Linux kernel; and finally the acquisition in October and November 2003 of Ximian and then SuSE by the American technology giant Novell.^[15]

[edit] Present day

Today Linux is used in numerous domains, from embedded systems^[16] to supercomputers,^[17] and has secured a place in server installations with the popular LAMP application stack.^[18] Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn develops 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 combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.

[edit] Adoption

Main article: Linux adoption

Many quantitative studies of open source software focus on topics including market share and reliability, with numerous studies specifically examining Linux.^[19] 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.^[20] The actual installed user base may be higher than indicated by this figure, as most Linux distributions and applications are freely available and redistributable.

Desktop adoption is weaker than server adoption, with diverse calculations generally figuring between 0.3% and 3% as a function of the sample set and calculation methods used.^{[citation needed]} According to market research company IDC, 25% of servers and 2.8% of desktop computers ran Linux as of 2004.^[21] The estimate of these numbers is driven by website traffic analysis, which may be complicated by two factors. First, many web browsers can modify their identity, either by default or via user action, by exploiting the user agent string, so as not to be blocked by websites that refuse to interact with browsers other than Internet Explorer running under Microsoft Windows. Second, a Linux system may be configured not to communicate this information for privacy and security reasons.

Linux Online alleges that people regard Linux as suitable mostly for computer experts because mainstream computer magazine reporters cannot explain what Linux is in a meaningful way, as they lack real life experience using it.^[22] Furthermore, 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. However, as of early 2007, significant progress in hardware compatibility has been made, and it is becoming increasingly common for hardware to work "out of the box" with many Linux distributions. Proponents and analysts attribute the relative success of Linux to its security, reliability,^[23] low cost, and freedom from vendor lock-in.^[24]

[edit] Naming

See also: History of the Linux kernel#The name

In 1992, Torvalds explained how he pronounces the word Linux:

“	'li' is pronounced with a short [ee] sound: compare prInt, mInImal etc. 'nux' is also short, non-diphtong, like in pUt. It's partly due to minix: linux was just my working name for the thing, and as I wrote it to replace minix on my system, the result is what it is... linus' minix became linux.	„
—Linus Torvalds, comp.os.linux newsgroup[25]

Torvalds has made available an audio sample which indicates his own pronunciation, in English (/ˈlɪnʊks/)^[26] and Swedish (/ˈlɪːnɤks/).^[27] English speakers may also pronounce the name as [ˈlaɪnʌks],^[28] /ˈlɪnʊks/, or /ˈlɪnəks/.^[29]

The Free Software Foundation views Linux distributions which use GNU software as "variants" of the GNU system, and they ask that such operating systems be referred to as GNU/Linux or a Linux-based GNU system.^[30] However, the media and population at large refers to this family of operating systems as Linux. While some distributors make a point of using the aggregate form, most notably Debian with the Debian GNU/Linux distribution, its 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: GNU/Linux naming controversy

[edit] Copyright and Trademark

The Linux kernel and most GNU software are licensed under the GNU General Public License (GPL), version 2. The GPL requires that all distributed source code modifications and derived works also be licensed under the GPL, and is sometimes referred to as a "share and share-alike" or "copyleft" license. In 1997, Linus Torvalds stated, "Making Linux GPL'd was definitely the best thing I ever did."^[31] Other software 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. After more than ten years, the Free Software Foundation announced that they would be upgrading the GPL to version 3, citing increasing concerns with software patents and digital rights management (DRM).^[32] In particular, DRM is appearing in systems running copyleft software, a phenomenon dubbed "tivoization" after digital video recorder maker Tivo's use of DRM in their Linux-based appliances.^[33] Linus Torvalds has publicly stated on the Linux Kernel Mailing List that, based on the drafts of the licence, he would not move the Linux kernel to GPL v.3, specifically citing the DRM provisions.^[34][35]

[edit] Source code analysis

A 2001 study of Red Hat Linux 7.1 found that this distribution contained 30 million source lines of code. Using the 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 means, it would have cost about 1.08 billion dollars (year 2000 U.S. dollars) to develop in the United States.^[36]

Most of the code (71%) was written in the C programming language, but many other languages were used, including C++, Lisp, assembly language, Perl, Fortran, Python and various shell scripting 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.^[36]

In a later study, the same analysis was performed for Debian GNU/Linux version 2.2.^[37] This distribution contained over fifty-five million source lines of code, and the study estimated that it would have cost 1.9 billion dollars (year 2000 U.S. dollars) to develop by conventional means.

In March 2003, the SCO Group filed a lawsuit against IBM, claiming that IBM had contributed parts of SCO's copyrighted code to the Linux kernel, violating IBM's license to use Unix. Also, SCO sent letters to several companies warning that their use of Linux without a license from SCO may be actionable, and claimed in the press that they would be suing individual Linux users. Per the Utah District Court ruling on July 3, 2006; 182 out of 294 items of evidence provided by SCO against IBM in discovery were dismissed.^[38]

See also: SCO-Linux controversies

[edit] Trademark

In the United States, the name Linux is a trademark registered to Linus Torvalds.^[39] 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 to have the trademark assigned to Torvalds, and in 1997 the case was settled.^[40] 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.^[41]

[edit] Philosophy

The primary difference between Linux and other contemporary operating systems is that the Linux kernel and other components are open source software. Linux is not the only such operating system, although it is the most well-known and widely used one. Some open source 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 is used for the Linux kernel itself: the GNU GPL written by Richard Stallman.

One of the advantages of open source, as proposed by Eric Raymond in The Cathedral and the Bazaar, is that it allows for rapid software bug detection and elimination, which is important for correcting security exploits. This argument rejects the notion of security through obscurity.

[edit] Interoperability

Linux aims for interoperability with other operating systems, and by extension the software that runs on Linux aims for interoperability with other Linux and non-Linux software. As an operating system underdog competing with mainstream operating systems, Linux cannot rely on a monopoly advantage; in order for Linux to be a convenient operating system for users that is commercially viable, it must interact well with non-Linux computers. Interoperability also provides users free choice of software and data formats whilst not restricting them as a result of that choice.

Linux systems adhere to POSIX, SUS, ISO, and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.^[42][43][44]

A priority is placed on open formats, public specifications for data that are freely available and free to implement, such that there can be multiple competing independent implementations to choose from, instead of only a single piece of software which can work with a specific format. These contrast with closed formats, which are either poorly documented or not documented at all, and for which there exists no agreement between competing vendors. When standards exist for network communication protocols, data formats, and APIs, they contribute to the robustness and adoption of Linux. In some cases, free software projects are the reference implementation of these protocols, examples being the Apache HTTP Server,^{[citation needed]} and the X.org implementation of the X Window System.

Examples of standard conformance include Mozilla Firefox which adheres strictly to World Wide Web Consortium recommendations, Jabber which formed the basis for the XMPP standard recognized by the Internet Engineering Task Force in the domain of instant messaging, and office productivity suites such as OpenOffice.org and KOffice which brought to light the recent OpenDocument standard.

In other domains, there are neither recognized standards nor organizations to manage them. The market is therefore split between software which attempts to interoperate as much as possible, and that which establishes market dominance through vendor lock-in, or the use of closed formats and communication protocols. Prime examples of the first category draw from the instant messaging war, which is ruled by multiprotocol software such as Gaim, Kopete, and Trillian. The second category of software is exemplified by Microsoft Office and its widely used closed file formats, and the Common Internet File System protocol which allow for files and printers to be shared between different computers on a Windows network.

In these cases, interoperability depends on reverse engineering, which requires a substantial investment on the part of developers. The legal status of reverse engineering varies from country to country; it may be illegal in the United States^{[citation needed]} but legal in Europe, provided the goal is limited to interoperability.^{[citation needed]} Today, as a result of reverse engineering, OpenOffice.org can read most .doc files, and Samba allows non-Windows machines to interact with a Windows network.

A further problem beyond reverse engineering is when interoperability is needed for a format or protocol that is technically encumbered by digital rights management or Trusted Computing, or legally restricted by software patents or laws such as the European Copyright Directive and Digital Millennium Copyright Act.

[edit] Portability

Linux is a portable operating system. While the Linux kernel was originally designed only for Intel 80386 microprocessors, it now runs on a more diverse range of computer architectures than any other operating system—^[45] from the hand-held ARM-based iPAQ to the mainframe IBM System z9, in devices ranging from supercomputers to mobile phones. Specialized distributions exist for less mainstream architectures. The ELKS kernel 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 including the Apple iPod. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as the iMac and PowerBook, Palm PDAs, GameCube, Xbox and even the Playstation Portable.

[edit] Community

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 RedHat does with Fedora Core.

In many cities and regions, local associations known as Linux Users Groups (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 a chatroom on the popular freenode IRC network that are open to anybody with an IRC client. Online forums are another means for support, with notable examples being LinuxQuestions.org and the Gentoo forums. Finally, every established free software project and Linux distribution has one or more mailing lists; commonly there will be a specific topic such as usage or development for a given list. The Linux Kernel Mailing List is a high-volume list where all Linux kernel development happens. SourceForge, Savannah, and Apache host many free and open source software projects using standard collaborative software.

Linux-based newsgroups are available via the Google Groups interface and also via news readers. There are also 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 Linux on the Free Software Foundation website.

People who contribute to free software are not all software developers, as exemplified by the GNOME and KDE projects; there are many non-development contributions needed, as is the case for any software product. Furthermore, the principles of free software and open source have had repercussions in other domains where collaboration is possible and the cost of making copies is marginal. Amongst the members of this open source culture are the Creative Commons movement initiated by Lawrence Lessig and the collaborative encyclopedia Wikipedia founded by Jimmy Wales.

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 IBM, 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. The business model of commercial suppliers is generally dependent on 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.

[edit] Distributions

Main article: Linux distribution

Free software projects, although developed in a 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.

A typical general purpose distribution includes the following:

1. A boot loader: A menu system that will allow the user to select which operating system to load in the process of booting a computer system. The most common bootloaders are LILO or GRUB.
2. Linux kernel: The core or heart of the operating system. The name of the OS comes from here.
3. GNU Compiler Collection: A set of tools that allow a programmer to write and compile program code and shell scripts.
4. GNU C Library
5. GNU bash shell, X Window System networking and display protocol and an accompanying desktop environment such as KDE, GNOME,or Xfce together with thousands of application software packages, from office suites to webservers to media players to 3D computer graphics software to text editors, and scientific programs.

As well as those designed for general purpose use, distributions may be specialized for different purposes including: computer architecture support, embedded systems, stability, security, localization to a specific region or language, targeting of specific user groups, support for 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.^[46]

[edit] Interface

[edit] Command line interface

Linux includes a command line interface (CLI) as part of its Unix-like functionality. Distributions specialized for servers or administration may use the CLI as their only interface, for the absence of a graphical user interface (GUI) helps to increase security and minimize system resource consumption. As well, Linux machines can run without a monitor attached. In order for a user to access them, either remote X11 usage is necessary, or the CLI must be used via a protocol such as SSH or telnet. On local networks, remote X11 usage is generally acceptable, but over long distances high network latency can make it impractical.

In the early history of Linux, many operations required CLI usage. The advent of distributions dedicated to desktop and family have changed this. However, online manuals for Linux often mention a CLI-based solution to a problem, even if a GUI-based alternative exists. The CLI is universal in the Linux world, whereas GUIs can differ from machine to machine. It also facilitates inter-operation between Linux and non-Linux machines which also have a CLI; Mac OS X machines are one example. It is also easier for an expert to help a user via the CLI if the user need only copy and paste the advice into a terminal.

Many important programs do not have a GUI, including most of the GNU userland. This comes from the Unix philosophy of designing a program to do one thing, and to do it well. The CLI is particularly suited for automation of repetitive or delayed tasks, and there is a natural progression where the command to perform a task is first issued directly, and then later reused in a script to provide automation.

Graphical and command line interfaces can also complement each other. There are a host of graphical terminal emulator programs, including xterm, rxvt, aterm, gnome-terminal, and konsole. For these programs, the X11 copy and paste mechanism can facilitate communication between the terminal and GUI applications.

[edit] X window managers

The traditional GUI for a Linux operating system is based on a stand-alone X window manager such as FVWM, Enlightenment, or Window Maker, and a suite of diverse applications running under it. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system. A high degree of flexibility allows for extensive customization, and the resource requirements in terms of CPU, memory, and hard-disk space consumption are lower than those of a full-fledged desktop environment.^{[citation needed]}

This model contrasts with that of platforms such as Mac OS, which were developed during the same era as the X window system. Under such platforms, the user interface is unified by a single toolkit that provides widgets for everything from buttons to window decorations such as title bars, manages window placement, and otherwise provides a consistent look and feel to the user. Because the X window managers only manage the placement of windows, their decoration, and some inter-process communication, the look and feel of individual applications may vary widely, especially if they use different graphical user interface toolkits.

[edit] Desktop environments

Main article: X Window System desktop environment

The use of window managers by themselves declined with the rise of Linux desktop environments. They combine a window manager with a suite of standard applications that adhere to human interface guidelines. Whereas a window manager is analogous to the Aqua user interface for OS X, a Linux desktop environment is analogous to Aqua as well as all of the default OS X graphical applications and configuration utilities. Initially, CDE was available as a proprietary solution, but was never popular on Linux systems due to cost and licensing restrictions.^{[citation needed]} In 1996 the KDE was announced, followed in 1997 by the announcement of GNOME. Xfce is a smaller project that was also founded in 1997, and focuses on speed and modularity. A comparison of X Window System desktop environments demonstrates the differences between environments.

[edit] Applications

[edit] Desktop

Under Linux, desktop software of high quality is in high demand; this includes applications such as word processors, spreadsheets, email clients, and web browsers. The following are the major Linux desktop applications:

• Office: StarOffice/OpenOffice.org. It may be useful to compare office suites.
• Internet: Firefox, Thunderbird, Evolution, Gaim, and Azureus
• Multimedia: VLC, MPlayer, Xine, XMMS, Totem, and Amarok
• Graphics: The GIMP, Inkscape, and Scribus

Although in specialized application domains such as desktop publishing and professional audio there may be a lack of commercial quality software, users migrating from Mac OS X and Windows can find equivalent applications for most tasks.^[47] Furthermore, it is uncommon for a free software project that works under Windows or Mac OS X not to have a Linux version; a user accustomed to using free software under Windows can generally expect to find the same applications running under Linux. A growing amount of proprietary desktop software is also supported under Linux,^[48] examples being Adobe Flash Player, Acrobat Reader, Nero Burning ROM, Opera, RealPlayer, and Skype. Additionally, Crossover Office is a commercial solution based on the open source WINE project that supports running Windows versions of Microsoft Office and Photoshop.

[edit] Games

Main article: Linux gaming

There are far fewer games available for Linux than for Windows, console systems, or Mac OS X; game development companies generally receive a lower return on investment when they support an operating system with a small market share. The Linux Gamers' Game List is a long but selective list,^[49] and The Linux Game Tome is a database with many entries that is less discriminating but has user comments and rankings.^[50]

There are few original open source games that have obtained notability, examples being NetHack and Tux Racer. Remakes and re-releases are more common, examples being Freeciv and The Ur-Quan Masters. In some cases, developers have released Linux ports of their games directly, with id Software recently releasing Quake 4. Independent companies have also taken on the task of porting prominent Windows games to Linux after their initial release. Loki Software was the first such company, founded in 1998, and superseded by Linux Game Publishing in 2001. WINE and the commercial Cedega fork allow many Windows games to run natively under Linux, and virtual machines and low-level machine emulators provide binary compatibility for games designed for other platforms.

Library support for Linux gaming is provided directly by OpenGL and ALSA, or by SDL, a cross-platform multimedia wrapper around system-dependent libraries. The DRI project provides open source video card drivers, and NVIDIA, and ATI also release binary kernel modules for their video cards. Linux runs on several game consoles, including the Xbox,^[51] Playstation 2, 3, and GameCube,^[52] which allows game developers without an expensive game development kit to access console hardware.

[edit] Comparison with Windows

Main article: Comparison of Windows and Linux

Due to the prevalence of Microsoft Windows on personal computers from the mid-1990s onwards, a comparison between Windows and Linux became a common topic of conversation among computer enthusiasts. In the past, Linux and other free software projects have been frequently criticized for not going far enough to ensure ease of use.^[53] Since then, there have been numerous independent studies and articles which indicate that a modern Linux desktop using either GNOME or KDE is on par with Microsoft Windows, even in a business setting.^[54]

Although lack of application support is often cited as a reason to use Windows over Linux, compatibility layers such as Wine or NdisWrapper and virtual machines like VirtualBox allow some Microsoft Windows applications and drivers to be used on Linux without requiring the vendor to adapt them. This allows users to more easily migrate from Windows to Linux since they can still run many of their Windows applications with little additional effort. Additionally, commercial software such as CrossOver have been developed which extend Wine to allow many commercial Windows applications to run in a Linux environment. In a similar fashion, Cygwin and Microsoft Windows Services for UNIX make it possible for users of Windows to run some GNU and other software normally only available on Linux and other Unix-like systems.

[edit] Servers, supercomputers and embedded devices

Historically, Linux has mainly been used as a 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 servers.^[55] This is due to its relative stability and long uptimes, 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 server-software combination (Linux, Apache, MySQL, Perl/PHP/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 supercomputers. As of January 5, 2007, out of the top 500 systems, 376 (75.2%) run Linux.^[56]

Due to its low cost and its high configurability, an embedded Linux is often used in embedded systems such as television set-top boxes, mobile phones, and handheld devices. Linux has become a major competitor to the proprietary Symbian OS found in many mobile phones (16.7% of smartphones sold worldwide during 3Q, 2006 were using Linux^[57]), and it is an alternative to the dominant Windows CE and Palm OS operating systems on handheld devices. The popular TiVo digital video recorder uses a customized version of Linux.^[58] Several network firewall and router standalone products, including several from Linksys, use Linux internally, using its advanced firewalling and routing capabilities. The Korg OASYS and the Yamaha Motif XS music workstations also run Linux.

[edit] Software development

Most Linux distributions support dozens of programming languages. Core system software such as libraries and basic utilities are usually written in C. Enterprise software is often written in C, C++, Java, Perl, Ruby, or Python. 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, C++, Java, and Fortran. The Linux kernel itself is written to be compiled with GCC.

Most distributions also include support for Perl, Ruby, Python and other dynamic languages. Examples of languages that are less common, but still well-supported, are C# via the Mono project, and Scheme. A number of Java Virtual Machines 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 widget toolkits, 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 environments available including Anjuta, Eclipse, KDevelop, MonoDevelop, NetBeans, and Omnis Studio while the traditional editors Vim and Emacs remain popular.^[59]

Although free and open source compilers and tools are widely used under Linux, there are also proprietary solutions available from a range of companies, including the Intel C++ Compiler, PathScale,^[60] Micro Focus COBOL,^[61] Franz Inc,^[62] and the Portland Group.^[63]

[edit] References

[edit] See also

• List of Linux distributions
• Comparison of Linux distributions
• List of Linux magazines
• The Cathedral and the Bazaar
• Total cost of ownership
• DistroWatch
• Linux software

[edit] External links

Find more information on Linux by searching Wikipedia's sister projects
	Dictionary definitions from Wiktionary
	Textbooks from Wikibooks
	Quotations from Wikiquote
	Source texts from Wikisource
	Images and media from Commons
	News stories from Wikinews
	Learning resources from Wikiversity

• The Linux Documentation Project — HOWTOs, FAQs and other guides
• The Linux Information Project (LINFO)
• Comprehensive Linux Textbook — free textbook
• Linux Knowledge Base and Tutorial
• The Linux Home Page at Linux Online — information and resources
• The Linux Kernel Archives — official site
• Linux Links - The Linux Portal — link site
• Linux Google search.
• The Linux Foundation.