Linux

This article is about the operating system. For thekernel, see Linux kernel. For other uses, see Linux(disambiguation).

Linux (pronounced i/ˈlɪnəks/ LIN-əks[4][5] or, lessfrequently, /ˈlaɪnəks/ LYN-əks[5][6]) is a Unix-like andmostly POSIX-compliant[7] computer operating system(OS) assembled under the model of free and open-sourcesoftware development and distribution. The definingcomponent of Linux is the Linux kernel,[8] an operatingsystem kernel first released on 5 October 1991 by LinusTorvalds.[9][10] The Free Software Foundation uses thenameGNU/Linux to describe the operating system, whichhas led to some controversy.[11][12]

Linux was originally developed as a free operating sys-tem for personal computers based on the Intel x86 ar-chitecture, but has since been ported to more computerhardware platforms than any other operating system.[13]

Thanks to its dominance on smartphones, Android, whichis built on top of the Linux kernel, has the largest installedbase of all general-purpose operating systems.[14] Linux,in its original form, is also the leading operating systemon servers and other big iron systems such as mainframecomputers and supercomputers,[15][16] but is used on onlyaround 1.5% of desktop computers[17] with Linux-basedChrome OS taking about 5% of the overall and nearly20% of the sub-$300 notebook sales.[18] Linux also runson embedded systems, which are devices whose oper-ating system is typically built into the firmware and ishighly tailored to the system; this includes smartphonesand tablet computers running Android and other Linuxderivatives,[19] TiVo and similar DVR devices, networkrouters, facility automation controls, televisions,[20][21]

video game consoles, and smartwatches.[22]

The development of Linux is one of the most prominentexamples of free and open-source software collabora-tion. The underlying source code may be used, modifiedand distributed—commercially or non-commercially—by anyone under the terms of its respective licenses, suchas the GNU General Public License. Typically, Linuxis packaged in a form known as a Linux distribution, forboth desktop and server use. Some of the popular main-stream Linux distributions are Debian, Ubuntu, LinuxMint, Fedora, openSUSE, Arch Linux and Gentoo, to-gether with commercial Red Hat Enterprise Linux andSUSE Linux Enterprise Server distributions. Linux dis-tributions include the Linux kernel, supporting utilitiesand libraries, and usually a large amount of applicationsoftware to fulfill the distribution’s intended use.

Distributions oriented toward desktop use typically in-clude X11, a Wayland implementation or Mir as thewindowing system, and an accompanying desktop envi-ronment such as GNOME or the KDE Software Compila-tion; some distributions may also include a less resource-intensive desktop such as LXDE or Xfce. Distributionsintended to run on servers may omit all graphical environ-ments from the standard install, and instead include othersoftware to set up and operate a solution stack such asLAMP. Because Linux is freely redistributable, anyonemay create a distribution for any intended use.

1 History

Main article: History of Linux

1.1 Antecedents

Linus Torvalds, principal author of the Linux kernel

The Unix operating system was conceived and im-plemented in 1969 at AT&T's Bell Laboratories inthe United States by Ken Thompson, Dennis Ritchie,

1

2 1 HISTORY

Douglas McIlroy, and Joe Ossanna.[23] First released in1971, Unix was written entirely in assembly language asit was common practice at the time. Later, in a key pio-neering approach in 1973, it was rewritten in the C pro-gramming language by Dennis Ritchie (with exceptionsto the kernel and I/O). The availability of a high-level lan-guage implementation of Unix made its porting to differ-ent computer platforms easier.Due to an earlier antitrust case forbidding it from en-tering the computer business, AT&T was required to li-cense the operating system’s source code to anyone whoasked.[24] As a result, Unix grew quickly and becamewidely adopted by academic institutions and businesses.In 1984, AT&T divested itself of Bell Labs; freed of thelegal obligation requiring free licensing, Bell Labs beganselling Unix as a proprietary product.The GNU Project, started in 1983 by Richard Stallman,had the goal of creating a “complete Unix-compatiblesoftware system” composed entirely of free software.Work began in 1984.[25] Later, in 1985, Stallman startedthe Free Software Foundation and wrote the GNU Gen-eral Public License (GNU GPL) in 1989. By the early1990s, many of the programs required in an operatingsystem (such as libraries, compilers, text editors, a Unixshell, and a windowing system) were completed, althoughlow-level elements such as device drivers, daemons, andthe kernel were stalled and incomplete.[26]

Linus Torvalds has said that if the GNU kernel had beenavailable at the time (1991), he would not have decidedto write his own.[27]

Although not released until 1992 due to legal compli-cations, development of 386BSD, from which NetBSD,OpenBSD and FreeBSD descended, predated that ofLinux. Torvalds has said that if 386BSD had been avail-able at the time, he probably would not have createdLinux.[28]

MINIX was created by a computer science professorAndrew S. Tanenbaum and released in 1987 as a minimalUnix-like operating system targeted at students and oth-ers who wanted to learn the operating system principles.Although the complete source code of MINIX was freelyavailable, the licensing terms prevented it from being freesoftware until the licensing changed in April 2000.[29]

1.2 Creation

In 1991, while attending the University of Helsinki, Tor-valds became curious about operating systems[30] andfrustrated by the licensing of MINIX, which at the timelimited it to educational use only.[29] He began to workon his own operating system kernel, which eventually be-came the Linux kernel.Torvalds began the development of the Linux kernel onMINIX and applications written for MINIX were alsoused on Linux. Later, Linux matured and further Linux

kernel development took place on Linux systems.[31]

GNU applications also replaced all MINIX components,because it was advantageous to use the freely availablecode from the GNU Project with the fledgling operat-ing system; code licensed under the GNU GPL can bereused in other projects as long as they also are releasedunder the same or a compatible license. Torvalds ini-tiated a switch from his original license, which prohib-ited commercial redistribution, to the GNU GPL.[32] De-velopers worked to integrate GNU components with theLinux kernel, making a fully functional and free operatingsystem.[26]

1.3 Naming

5.25-inch floppy discs holding a very early version of Linux

Linus Torvalds had wanted to call his invention Freax, aportmanteau of “free”, “freak”, and “x” (as an allusionto Unix). During the start of his work on the system, hestored the files under the name “Freax” for about half of ayear. Torvalds had already considered the name “Linux,”but initially dismissed it as too egotistical.[33]

In order to facilitate development, the files were uploadedto the FTP server (ftp.funet.fi) of FUNET in September1991. Ari Lemmke, Torvald’s coworker at the HelsinkiUniversity of Technology (HUT) who was one of thevolunteer administrators for the FTP server at the time,did not think that “Freax” was a good name. So, henamed the project “Linux” on the server without consult-ing Torvalds.[33] Later, however, Torvalds consented to“Linux”.To demonstrate how the word “Linux” should be pro-nounced ( i/ˈlɪnəks/ LIN-əks[4][5]), Torvalds included anaudio guide ( listen ) with the kernel source code.[34]

Another variant of pronunciation is /ˈlaɪnəks/ LYN-əks.[5][6]

1.5 Current development 3

1.4 Commercial and popular uptake

Ubuntu, a popular Linux distribution

Main article: Linux adoptionAdoption of Linux in production environments, rather

Nexus 5 running Android

than being used only by hobbyists, started to take offfirst in the mid-1990s in the supercomputing community,where organizations such as NASA started to replacetheir increasingly expensive machines with clusters of in-expensive commodity computers running Linux. Com-mercial use followed when Dell and IBM, followed byHewlett-Packard, started offering Linux support to es-cape Microsoft's monopoly in the desktop operating sys-tem market.[35]

Today, Linux systems are used in every domain, fromembedded systems to supercomputers,[16][36] and havesecured a place in server installations often using thepopular LAMP application stack.[37] Use of Linux dis-tributions in home and enterprise desktops has beengrowing.[38][39][40][41][42][43][44] Linux distributions havealso become popular in the netbook market, with manydevices shipping with customized Linux distributions in-stalled, and Google releasing their own Google ChromeOS designed for netbooks.Linux’s greatest success in the consumer market is per-haps the mobile device market, with Android being oneof the most dominant operating systems on smartphonesand very popular on tablets and, more recently, on

wearables. Linux gaming is also on the rise with Valveshowing its support for Linux and rolling out its own gam-ing oriented Linux distribution. Linux distributions havealso gained popularity with various local and national gov-ernments, such as the federal government of Brazil.[45]

1.5 Current development

Torvalds continues to direct the development ofthe kernel.[46] Stallman heads the Free SoftwareFoundation,[47] which in turn supports the GNUcomponents.[48] Finally, individuals and corporationsdevelop third-party non-GNU components. These third-party components comprise a vast body of work and mayinclude both kernel modules and user applications andlibraries.Linux vendors and communities combine and distributethe kernel, GNU components, and non-GNU compo-nents, with additional package management software inthe form of Linux distributions.

2 Design

A Linux-based system is a modular Unix-like operat-ing system, deriving much of its basic design from prin-ciples established in Unix during the 1970s and 1980s.Such a system uses a monolithic kernel, the Linux kernel,which handles process control, networking, access to theperipherals, and file systems. Device drivers are eitherintegrated directly with the kernel, or added as modulesthat are loaded while the system is running.[49]

Separate projects that interface with the kernel providemuch of the system’s higher-level functionality. TheGNU userland is an important part of most Linux-basedsystems, providing the most common implementation ofthe C library, a popular CLI shell, and many of the com-mon Unix tools which carry out many basic operating sys-tem tasks. The graphical user interface (or GUI) used bymost Linux systems is built on top of an implementationof the X Window System.[50] More recently, the Linuxcommunity seeks to advance to Wayland as the new dis-play server protocol in place of X11; Ubuntu, however,develops Mir instead of Wayland.[51]

Installed components of a Linux system include thefollowing:[50][52]

• A bootloader, for example GNU GRUB, LILO,SYSLINUX, Coreboot or Gummiboot. This is aprogram that loads the Linux kernel into the com-puter’s main memory, by being executed by thecomputer when it is turned on and after the firmwareinitialization is performed.

• An init program, such as the traditional sysvinit andthe newer systemd, OpenRC and Upstart. This is the

4 2 DESIGN

first process launched by the Linux kernel, and is atthe root of the process tree: in other terms, all pro-cesses are launched through init. It starts processessuch as system services and login prompts (whethergraphical or in terminal mode).

• Software libraries, which contain code that can beused by running processes. On Linux systems us-ing ELF-format executable files, the dynamic linkerthat manages use of dynamic libraries is known asld-linux.so. If the system is set up for the user tocompile software themselves, header files will alsobe included to describe the interface of installed li-braries. Beside the most commonly used software li-brary on Linux systems, the GNU C Library (glibc),there are numerous other libraries.

• C standard library is the library needed to runstandard C programs on a computer system,with the GNU C Library being the most com-monly used. Several alternatives are available,such as the EGLIBC (which was used by De-bian for some time) and uClibc (which was de-signed for uClinux).

• Widget toolkits are the libraries used to buildgraphical user interfaces (GUIs) for softwareapplications. Numerous widget toolkits areavailable, including GTK+ and Clutter (soft-ware) developed by the GNOME project,Qt developed by the Qt Project and ledby Digia, and Enlightenment Foundation Li-braries (EFL) developed primarily by theEnlightenment team.

• User interface programs such as command shells orwindowing environments.

2.1 User interface

The user interface, also known as the shell, is either acommand-line interface (CLI), a graphical user inter-face (GUI), or through controls attached to the associ-ated hardware, which is common for embedded systems.For desktop systems, the default mode is usually a graph-ical user interface, although the CLI is available throughterminal emulator windows or on a separate virtual con-sole.CLI shells are the text-based user interfaces, which usetext for both input and output. The dominant shell used inLinux is the GNU Bourne-Again Shell (bash), originallydeveloped for the GNU project. Most low-level Linuxcomponents, including various parts of the userland, usethe CLI exclusively. The CLI is particularly suited forautomation of repetitive or delayed tasks, and providesvery simple inter-process communication.On desktop systems, the most popular user interfacesare the GUI shells, packaged together with extensive

Bash, a shell developed by GNU[53] and widely used in Linux

desktop environments, such as the K Desktop Envi-ronment (KDE), GNOME, Cinnamon, Unity, LXDE,Pantheon and Xfce, though a variety of additional user in-terfaces exist. Most popular user interfaces are based onthe X Window System, often simply called “X”. It pro-vides network transparency and permits a graphical appli-cation running on one system to be displayed on anotherwhere a user may interact with the application; however,certain extensions of the X Window System are not ca-pable of working over the network.[54] Several popular Xdisplay servers exist, with the reference implementation,X.Org Server, being the most popular.Several types of window managers exist for X11, includ-ing tiling, dynamic, stacking and compositing. Windowmanagers provide means to control the placement and ap-pearance of individual application windows, and interactwith the X Window System. Simpler X window man-agers such as dwm or ratpoison provide a minimalist func-tionality, while more elaborate window managers such asFVWM, Enlightenment or Window Maker provide morefeatures such as a built-in taskbar and themes, but arestill lightweight when compared to desktop environments.Desktop environments include window managers as partof their standard installations, such as Mutter (GNOME),KWin (KDE) or Xfwm (xfce), although users may chooseto use a different window manager if preferred.Wayland is a display server protocol intended as a re-placement for the X11 protocol; as of 2014, Waylandhas not received wider adoption. Unlike X11, Waylanddoes not need an external window manager and composit-ing manager. Therefore, a Wayland compositor takes therole of the display server, window manager and composit-ing manager. Weston is the reference implementation ofWayland, while GNOME’s Mutter and KDE’s KWin arebeing ported to Wayland as standalone display servers.

3.1 Community 5

Enlightenment has already been successfully ported toWayland since version 19.

2.2 Video input infrastructure

Main article: Video4Linux

Linux currently has two modern kernel-userspace APIsfor handing video input devices: V4L2 API for videostreams and radio, and DVB API for digital TVreception.[55]

Due to the complexity and diversity of different devices,and due to the large amount of formats and standards han-dled by those APIs, this infrastructure needs to evolve tobetter fit other devices. Also, a good userspace devicelibrary is the key of the success for having userspace ap-plications to be able to work with all formats supportedby those devices.[56][57]

3 Development

System III & V family

BSD (Berkeley Software Distribution)

FreeBSD

NetBSD

OpenBSD

SunOS

Solaris

NextStepMac OS X

Xenix OS

GNU

GNU/Linux

Commercial UNIX

HP-UX

AIX

UnixWare

IRIX

BSD family

1970 1980 1990 2000 Time

Microsoft/SCO

Richard Stallman

Darwin

GNU/Hurd K16

Linus Torvalds

Andrew S. Tanenbaum

Minix

9.1

6.0.1

5.3

11 11/11

10.8.43.3

3.10.9

3.2.1

11i v3

7.1 TL1

6.5.30

4.1.4

Research UNIX 10.5

Bell Labs: Ken Thompson,Dennis Ritchie, et al.

Bill Joy

Sun Microsystems

AT&T

IBM

SGI

Univel/SCO

Apple

2010

4.4

Simplified history of Unix-like operating systems. Linux sharessimilar architecture and concepts (as part of the POSIX standard)but does not share non-free source code with the original Unix orMINIX.

Main articles: Linux distribution and Free software

The primary difference between Linux and many otherpopular contemporary operating systems is that the Linuxkernel and other components are free and open-sourcesoftware. Linux is not the only such operating system,although it is by far the most widely used.[58] Some freeand open-source software licenses are based on the prin-ciple of copyleft, a kind of reciprocity: any work derivedfrom a copyleft piece of software must also be copyleftitself. The most common free software license, the GNUGeneral Public License (GPL), is a form of copyleft, andis used for the Linux kernel and many of the componentsfrom the GNU Project.

Linux based distributions are intended by developersfor interoperability with other operating systems and es-tablished computing standards. Linux systems adhereto POSIX,[59] SUS,[60] LSB, ISO, and ANSI standardswhere possible, although to date only one Linux distribu-tion has been POSIX.1 certified, Linux-FT.[61][62]

Free software projects, although developed throughcollaboration, are often produced independently of eachother. The fact that the software licenses explicitly permitredistribution, however, provides a basis for larger scaleprojects that collect the software produced by stand-aloneprojects and make it available all at once in the form of aLinux distribution.Many Linux distributions, or “distros”, manage a remotecollection of system software and application softwarepackages available for download and installation througha network connection. This allows users to adapt the op-erating system to their specific needs. Distributions aremaintained by individuals, loose-knit teams, volunteerorganizations, and commercial entities. A distribution isresponsible for the default configuration of the installedLinux kernel, general system security, and more gener-ally integration of the different software packages intoa coherent whole. Distributions typically use a packagemanager such as apt, yum, zypper, pacman or portage toinstall, remove and update all of a system’s software fromone central location.

3.1 Community

See also: Free software community and Linux UserGroup

A distribution is largely driven by its developer and usercommunities. Some vendors develop and fund their dis-tributions on a volunteer basis, Debian being a well-known example. Others maintain a community versionof their commercial distributions, as Red Hat does withFedora and SUSE does with openSUSE.In many cities and regions, local associations known asLinux User Groups (LUGs) seek to promote their pre-ferred distribution and by extension free software. Theyhold meetings and provide free demonstrations, train-ing, technical support, and operating system installationto new users. Many Internet communities also providesupport to Linux users and developers. Most distri-butions and free software / open-source projects haveIRC chatrooms or newsgroups. Online forums are an-other means for support, with notable examples beingLinuxQuestions.org and the various distribution specificsupport and community forums, such as ones for Ubuntu,Fedora, and Gentoo. Linux distributions host mailinglists; commonly there will be a specific topic such as us-age or development for a given list.There are several technology websites with a Linux

6 4 HARDWARE SUPPORT

focus. Print magazines on Linux often includecover disks including software or even complete Linuxdistributions.[63][64]

Although Linux distributions are generally available with-out charge, several large corporations sell, support, andcontribute to the development of the components of thesystem and of free software. An analysis of the Linux ker-nel showed 75 percent of the code from December 2008to January 2010 was developed by programmers workingfor corporations, leaving about 18 percent to volunteersand 7% unclassified.[65] Major corporations that providecontributions include Dell, IBM, HP, Oracle, Sun Mi-crosystems (now part of Oracle), SUSE, and Nokia. Anumber of corporations, notably Red Hat, Canonical, andSUSE, have built a significant business around Linux dis-tributions.The free software licenses, on which the various soft-ware packages of a distribution built on the Linux kernelare based, explicitly accommodate and encourage com-mercialization; the relationship between a Linux distri-bution as a whole and individual vendors may be seenas symbiotic. One common business model of com-mercial suppliers is charging for support, especially forbusiness users. A number of companies also offer aspecialized business version of their distribution, whichadds proprietary support packages and tools to adminis-ter higher numbers of installations or to simplify admin-istrative tasks.Another business model is to give away the software inorder to sell hardware. This used to be the norm in thecomputer industry, with operating systems such as CP/M,Apple DOS and versions of Mac OS prior to 7.6 freelycopyable (but not modifiable). As computer hardwarestandardized throughout the 1980s, it became more diffi-cult for hardware manufacturers to profit from this tactic,as the OS would run on any manufacturer’s computer thatshared the same architecture.

3.2 Programming on Linux

Linux distributions support dozens of programming lan-guages. The original development tools used for build-ing both Linux applications and operating system pro-grams are found within the GNU toolchain, which in-cludes the GNU Compiler Collection (GCC) and theGNU build system. Amongst others, GCC provides com-pilers for Ada, C, C++, Go and Fortran. Many program-ming languages have a cross-platform reference imple-mentation that supports Linux, for example PHP, Perl,Ruby, Python, Java, Go, Rust and Haskell. First re-leased in 2003, the LLVM project provides an alterna-tive cross-platform open-source compiler for many lan-guages. Proprietary compilers for Linux include the IntelC++ Compiler, Sun Studio, and IBM XL C/C++ Com-piler. BASIC in the form of Visual Basic is supportedin such forms as Gambas, FreeBASIC, and XBasic, and

in terms of terminal programming or QuickBASIC orTurbo BASIC programming in the form of QB64.A common feature of Unix-like systems, Linux includestraditional specific-purpose programming languages tar-geted at scripting, text processing and system configura-tion and management in general. Linux distributions sup-port shell scripts, awk, sed and make. Many programsalso have an embedded programming language to supportconfiguring or programming themselves. For example,regular expressions are supported in programs like grep,or locate, while advanced text editors, like GNU Emacs,have a complete Lisp interpreter built-in.Most distributions also include support for PHP, Perl,Ruby, Python and other dynamic languages. While not ascommon, Linux also supports C# (via Mono), Vala, andScheme. A number of Java Virtual Machines and devel-opment kits run on Linux, including the original Sun Mi-crosystems JVM (HotSpot), and IBM’s J2SE RE, as wellas many open-source projects like Kaffe and JikesRVM.GNOME and KDE are popular desktop environmentsand provide a framework for developing applications.These projects are based on the GTK+ and Qt widgettoolkits, respectively, which can also be used indepen-dently of the larger framework. Both support a wide va-riety of languages. There are a number of Integrateddevelopment environments available including Anjuta,Code::Blocks, CodeLite, Eclipse, Geany, ActiveStateKomodo, KDevelop, Lazarus, MonoDevelop, NetBeans,and Qt Creator, while the long-established editors Vim,nano and Emacs remain popular.[66]

4 Hardware support

Hardware

Desktop ComputerWorkstation

Home ComputerDesktop replacement laptop

Thin client

Mobile computerNote-/ Net-/ Smartbook

TabletSmartphone

PDA / Handheld game console

Wearable ComputerWristwatch

Virtual Retina DisplayHead-mounted display

Embedded ComputerCustomer-premises equipment

Measurement EquipmentLaboratory Equipment

Layer3-Switchesother embedded systems

SupercomputerComputer Cluster

Mainframe computer

Linux Network scheduler

Network stackNetfilter

Linux device drivers

Linux file system drivers

Linux Process Scheduler

Linux Security Modules

Linux kernelHuman-Machine-

Interface

Speech recognitionAttitude sensorMotion sensor

Display, SoundVibration

Keyboard & Mousealso Braille, Touch-Display, Speech recognition,Graphics tablet, 3D-Mouse, Wii nunchak, etc.

Touch-DisplayAttitude sensor, Motion sensor,Speech recognition

remote(SSH, HTTP, ...)

remote(SSH, HTTP,Serial, I2C, ...)

Pool of

free a

nd

op

en

-sou

rce a

nd

pro

pri

eta

ry s

oft

ware

High-performance computing(HPC)

Real-time computing(RTC)

Gra

ph

ical U

ser

Inte

rfaces

(Sh

ells)

Distributed computing

Wearable UI

Touch UI

Desktop UI

OfficeImage Processing

Desktop Publishing (DTP)

Digital Audio WorkstationDJ Mixing Software

Software DevelopmentPackage management systems

Web server solution stacks (LAMP)

Routing daemons

Home cinema solutions

Distributed Computing

CAD, CAM & CAE Software

Win

dow

ing

Syste

ms

Video processing software3D computer graphicsComputer animation

Motion graphics

Debian software archives: 37,000software packages

Video games

Linux is ubiquitously found on various types of hardware.

See also: List of Linux-supported computer architectures

Linux kernel is a widely ported operating system kernel;it runs on a highly diverse range of computer architec-tures, including the hand-held ARM-based iPAQ and theIBM mainframes System z9 or System z10 – covering de-vices ranging from mobile phones to supercomputers.[67]

Specialized distributions and kernel forks exist for lessmainstream architectures; for example, the ELKS ker-

5.1 Desktop 7

nel fork can run on Intel 8086 or Intel 80286 16-bit mi-croprocessors, while the µClinux kernel fork may runon systems without a memory management unit. Thekernel also runs on architectures that were only ever in-tended to use a manufacturer-created operating system,such as Macintosh computers (with both PowerPC andIntel processors), PDAs, video game consoles, portablemusic players, and mobile phones.There are several industry associations and hardwareconferences devoted to maintaining and improvingsupport for diverse hardware under Linux, such asFreedomHEC. Over time, support for different hardwarehas improved in Linux, resulting in any off-the-shelf pur-chase having a “good chance” of being compatible.[68]

5 Uses

See also: Linux range of use

Beside the Linux distributions designed for general-purpose use on desktops and servers, distributions maybe specialized for different purposes including: computerarchitecture support, embedded systems, stability, secu-rity, localization to a specific region or language, target-ing of specific user groups, support for real-time appli-cations, or commitment to a given desktop environment.Furthermore, some distributions deliberately include onlyfree software. As of 2015, over four hundred Linux dis-tributions are actively developed, with about a dozen dis-tributions being most popular for general-purpose use.[69]

5.1 Desktop

libinput

possibly adaptations to Wayland/Mir possibly adaptations to Wayland/Mir possibly adaptations to Wayland/Mir

libxserver

X-ServerX.Org

Xfree86

X-Win32X11.app

windowmanagermetacitymutterKWinCompiz

Linux kernel, device drivers & other modules

netfilter

radeon nouveau lima etna_viv freedreno tegra-re

? kdbus ?evdev kms (Kernel Mode Setting)

Hardware

drm (Direct Rendering Manager)

D-B

us-

Daem

on

CPU & GPUcache coherent L2-Caches

main memory

Keyboard & MouseTouch-ScreenBrailleDisplay

Ethernet802.11-(abc)Bluetooth

UMTS/CDMA/LTEGPS-receiverG-sensor

syst

em

d(c

onta

ins

ud

ev)

unetw

ork

Netw

ork

Manag

er

pack

ag

eki

td

Puls

eA

ud

io-d

ALSA: emu20k1, ctxfi, hda... ath9k

kmod-fs-ext4

kmod-ltq-atm-vr9

Media Application 3D Application2D Application

SELinuxTOMOYOSmack

AppArmor

ud

isks

System daemons:

avahi-

daem

on

User Interface Toolkits (in the form of libraries):

glibcµClibc

GLibGObject

GlibGModuleGThread

GIO

System libraries:

libwayland-server

Wayland Compositor

weston, clayton, mutter, KWin

GN

OM

E S

hell

Pla

sma 2

Cair

o-D

ock

Cin

nam

on

Desktop Shells:

Display server:

Qtlibwayland-client

GTK+Pango

Cairo (Xr)libwayland / COGL

ATK EFLlibwayland-client

SDLlibwayland-client

Alternative display servers:

D e s k t o p w i d g e t s

Enlig

ht.

DR

19

SFSurfaceFlinger

windowmanager

AWM

libmir-serv

mirmir window

managerCompiz

libbioniclibhybris

Unit

y

Ubuntu Android

Widgets forUnity and Plasma

Clutter

GNUstepwxWidgets

FLTK...

libwayland-clientlibX/libXCB

Linux kernel(Android-forked)

binder ashmem pmemloggerwakelocks ...

Visible software components of the Linux desktop stack in-clude the display server, widget engines, and some of the morewidespread widget toolkits. There are also components not di-rectly visible to end users, including D-Bus and PulseAudio.

See also: Desktop environment and Linux adoption:Measuring desktop adoption

The popularity of Linux on standard desktop computersand laptops has been increasing over the years.[70] Cur-rently most distributions include a graphical user envi-ronment, with the two most popular environments beingGNOME (which can utilize additional shells such as the

default GNOME Shell and Ubuntu Unity), and the KDEPlasma Desktop.No single official Linux desktop exists: rather desk-top environments and Linux distributions select compo-nents from a pool of free and open-source software withwhich they construct a GUI implementing some more orless strict design guide. GNOME, for example, has itshuman interface guidelines as a design guide, which givesthe human–machine interface an important role, not justwhen doing the graphical design, but also when consid-ering people with disabilities, and even when focusing onsecurity.[71]

The collaborative nature of free software development al-lows distributed teams to perform language localizationof some Linux distributions for use in locales where local-izing proprietary systems would not be cost-effective. Forexample, the Sinhalese language version of the Knoppixdistribution became available significantly before Mi-crosoft translated Windows XP into Sinhalese. In thiscase the Lanka Linux User Group played a major part indeveloping the localized system by combining the knowl-edge of university professors, linguists, and local devel-opers.

5.1.1 Performance and applications

The performance of Linux on the desktop has been acontroversial topic; for example in 2007 Con Kolivas ac-cused the Linux community of favoring performance onservers. He quit Linux kernel development out of frus-tration with this lack of focus on the desktop, and thengave a “tell all” interview on the topic.[72] Since then asignificant amount of development has focused on im-proving the desktop experience. Projects such as Upstartand systemd aim for a faster boot time; the Wayland andMir projects aim at replacing X11 while enhancing desk-top performance, security and appearance.[73]

Many popular applications are available for a wide vari-ety of operating systems. For example, Mozilla Firefox,OpenOffice.org/LibreOffice and Blender have download-able versions for all major operating systems. Further-more, some applications initially developed for Linux,such as Pidgin, and GIMP, were ported to other operatingsystems (including Windows and Mac OS X) due to theirpopularity. In addition, a growing number of proprietarydesktop applications are also supported on Linux,[74] suchas Autodesk Maya, Softimage XSI and Apple Shake inthe high-end field of animation and visual effects; see theList of proprietary software for Linux for more details.There are also several companies that have ported theirown or other companies’ games to Linux, with Linux alsobeing a supported platform on both the popular Steamand Desura digital-distribution services.[75]

Many other types of applications available for MicrosoftWindows and Mac OS X also run on Linux. Commonly,either a free software application will exist which does the

8 5 USES

functions of an application found on another operatingsystem, or that application will have a version that workson Linux, such as with Skype and some video games likeDota 2 and Team Fortress 2. Furthermore, the Wineproject provides a Windows compatibility layer to rununmodified Windows applications on Linux. It is spon-sored by commercial interests including CodeWeavers,which produces a commercial version of the software.Since 2009, Google has also provided funding to theWine project.[76][77] CrossOver, a proprietary solutionbased on the open-source Wine project, supports run-ning Windows versions of Microsoft Office, Intuit appli-cations such as Quicken and QuickBooks, Adobe Photo-shop versions through CS2, and many popular games suchas World of Warcraft. In other cases, where there is noLinux port of some software in areas such as desktop pub-lishing[78] and professional audio,[79][80][81] there is equiv-alent software available on Linux.

5.1.2 Components and installation

Besides externally visible components, such as X windowmanagers, a non-obvious but quite central role is playedby the programs hosted by freedesktop.org, such as D-Bus or PulseAudio; both major desktop environments(GNOME and KDE) include them, each offering graph-ical front-ends written using the corresponding toolkit(GTK+ or Qt). A display server is another component,which for the longest time has been communicating inthe X11 display server protocol with its clients; promi-nent software talking X11 includes the X.Org Server andXlib. Frustration over the cumbersome X11 core proto-col, and especially over its numerous extensions, has ledto the creation of a new display server protocol, Wayland.Installing, updating and removing software in Linux istypically done through the use of package managers suchas the Synaptic Package Manager, PackageKit, and YumExtender. While most major Linux distributions have ex-tensive repositories, often containing tens of thousandsof packages, not all the software that can run on Linuxis 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 thesemethods come with different degrees of difficulty; com-piling the source code is in general considered a challeng-ing process for new Linux users, but it is hardly neededin modern distributions and is not a method specific toLinux.

• Samples of graphical desktop environments

• Cinnamon

• Common Desktop Environment (CDE)

• Enlightenment

• GNOME Shell (GNOME 3)

• KDE Plasma (KDE 4)

• LXDE

• MATE (GNOME 2)

• Pantheon

• Sugar

• Trinity (KDE 3)

• Unity

• Xfce

5.2 Netbooks

Linux distributions have also become popular in thenetbook market, with many devices such as the ASUSEee PC and Acer Aspire One shipping with customizedLinux distributions installed.[82]

In 2009, Google announced its Google Chrome OS, aminimal Linux based operating system which applicationconsists only of the Google Chrome browser, a file man-ager and a media player.[83] The netbooks that shippedwith the operating system, termed Chromebooks, startedappearing in the market in June 2011.[84]

5.3 Servers, mainframes and supercom-puters

Web server

Linux kernel Hardware Environment: CCC

Networkinghardware

CPU&

RAM

SATASASRAIDiSCSINAS

Internet

kmod-fs-ext4kmod-fs-btrfs

Lustre...

Responseslow latency

Attacksstave off

&Requests

serve

Netfilter

NICdevicedriver

Process Scheduler

BotnetsDDoS-Attacks

Competitorscompete for customers

CrackersBotnets for DDoS-attacks

cracking attempts...

Customerswant attendanceStorage

CGI scripting

Database

Network scheduler

Linux network stack

AppArmorSELinux

SmackTOMOYO

MariaDB

MySQLDrizzle

Perl

PHP

Python

ApacheCherokeeLighttpdNginx

SquidPolipoTraffic server

Web cache

Broad overview of the LAMP software bundle, displayed heretogether with Squid. A high-performance and high-availabilityweb server solution providing security in a hostile environment.

Linux distributions have long been used as server oper-ating systems, and have risen to prominence in that area;Netcraft reported in September 2006, that eight of the tenmost reliable internet hosting companies ran Linux distri-butions on their web servers.[85] Since June 2008, Linuxdistributions represented five of the top ten, FreeBSDthree of ten, and Microsoft two of ten;[86] since Febru-ary 2010, Linux distributions represented six of the topten, FreeBSD two of ten, and Microsoft one of ten.[87]

Linux distributions are the cornerstone of theLAMP server-software combination (Linux, Apache,

5.5 Embedded devices 9

MariaDB/MySQL, Perl/PHP/Python) which hasachieved popularity among developers, and which is oneof the more common platforms for website hosting.[88]

Linux distributions have become increasingly popular onmainframes in the last decade partly due to pricing andthe open-source model.[16] In December 2009, computergiant IBM reported that it would predominantly marketand sell mainframe-based Enterprise Linux Server.[89]

Linux distributions are also commonly used as operatingsystems for supercomputers; in the decade since EarthSimulator supercomputer, all the fastest supercomputershave used Linux. As of November 2014, 97% of theworld’s 500 fastest supercomputers run some variant ofLinux,[90] including the top 80.[91]

5.4 Smart devices

Android smartphones

Several operating systems for smart devices, such assmartphones, tablet computers, smart TVs, and in-vehicleinfotainment (IVI) systems, are based on Linux. Majorplatforms for such systems include Android, Firefox OS,Mer and Tizen.Android has become the dominant mobile operating sys-tem for smartphones, during the second quarter of 2013,79.3% of smartphones sold worldwide used Android.[92]

Android is also a popular operating system for tablets, andAndroid smart TVs and in-vehicle infotainment systemshave also appeared in the market.Cell phones and PDAs running Linux on open-sourceplatforms became more common from 2007; examplesinclude the Nokia N810, Openmoko's Neo1973, and theMotorola ROKR E8. Continuing the trend, Palm (lateracquired by HP) produced a new Linux-derived operat-ing system, webOS, which is built into its line of PalmPre smartphones.Nokia's Maemo, one of the earliest mobile operating sys-tems, was based on Debian.[93] It was later merged withIntel's Moblin, another Linux-based operating system, toform MeeGo.[94] The project was later terminated in fa-

vor of Tizen, an operating system targeted at mobile de-vices as well as in-vehicle infotainment (IVI). Tizen is aproject within The Linux Foundation. Several Samsungproducts are already running Tizen, Samsung Gear 2 be-ing the most significant example.[95] Samsung Z smart-phones will use Tizen instead of Android.[96]

As a result of MeeGo’s termination, the Mer projectforked the MeeGo codebase to create a basis for mobile-oriented operating systems.[97] In July 2012, Jolla an-nounced Sailfish OS, their own mobile operating systembuilt upon Mer technology.Mozilla’s Firefox OS consists of the Linux kernel, ahardware abstraction layer, a web standards based run-time environment and user interface, and an integratedweb browser.[98]

Canonical has released Ubuntu Touch, its own mobileoperating system that aims to bring convergence to theuser experience on the operating system and its desk-top counterpart, Ubuntu. The operating system also pro-vides a full Ubuntu desktop when connected to an exter-nal monitor.[99]

5.5 Embedded devices

See also: Embedded Linux and Linux devicesDue to its low cost and ease of customization, Linux

The Jolla Phone has the Linux-based Sailfish OS

is often used in embedded systems. In the non-mobile telecommunications equipment sector, the ma-jority of customer-premises equipment (CPE) hardwareruns some Linux-based operating system. OpenWrt isa community driven example upon which many of theOEM firmwares are based.For example, the popular TiVo digital video recorderalso uses a customized Linux,[101] as do several networkfirewalls and routers from such makers as Cisco/Linksys.The Korg OASYS, the Korg KRONOS, the YamahaMotif XS/Motif XF music workstations,[102] YamahaS90XS/S70XS, Yamaha MOX6/MOX8 synthesizers,Yamaha Motif-Rack XS tone generator module, andRoland RD-700GX digital piano also run Linux. Linux

10 5 USES

In-car entertainment system of the Tesla Model S is based onUbuntu[100]

Nokia X, a smartphone that runs Linux kernel

is also used in stage lighting control systems, such as theWholeHogIII console.[103]

5.6 Gaming

Main article: Linux gaming

There had been several games that run on traditionaldesktop Linux, and many of which originally written fordesktop OS. However, due to most game developers notpaying attention to such a small market as desktop Linux,only a few prominent games have been available for desk-top Linux. On the other hand, as a popular mobile plat-form, Android has gained much developer interest andthere are many games available for Android.On 14 February 2013, Valve released a Linux ver-sion of Steam, a popular game distribution platform onPC.[104] Many Steam games were ported to Linux.[105]

On 13 December 2013, Valve released SteamOS, a gam-ing oriented OS based on Debian, for beta testing, andhas plans to ship Steam Machines as a gaming andentertainment platform.[106] Valve has also developedVOGL, an OpenGL debugger intended to aid video gamedevelopment,[107] as well as porting its Source game en-gine to desktop Linux.[108] As a result of Valve’s effort,several prominent games such as DotA 2, Team Fortress2, Portal, Portal 2 and Left 4 Dead 2 are now nativelyavailable on desktop Linux.On 31 July 2013, Nvidia released Shield as an attempt touse Android as a specialized gaming platform.[109]

5.7 Specialized uses

Due to the flexibility, customizability and free and open-source nature of Linux, it becomes possible to highly tuneLinux for a specific purpose. There are two main meth-ods for creating a specialized Linux distribution: buildingfrom scratch or from a general-purpose distribution as abase. The distributions often used for this purpose in-clude Debian, Fedora, Ubuntu (which is itself based onDebian), Arch Linux, Gentoo, and Slackware. In con-trast, Linux distributions built from scratch do not havegeneral-purpose bases; instead, they focus on the JeOSphilosophy by including only necessary components andavoiding resource overhead caused by components con-sidered redundant in the distribution’s use cases.

5.7.1 Home theater PC

A home theater PC (HTPC) is a PC that is mainly used asan entertainment system, especially a Home theater sys-tem. It is normally connected to a television, and oftenan additional audio system.OpenELEC, a Linux distribution that incorporates themedia center software Kodi, is an OS tuned specificallyfor an HTPC. Having been built from the ground up ad-hering to the JeOS principle, the OS is very lightweightand very suitable for the confined usage range of an

11

HTPC.There are also special editions of Linux distributionsthat include the MythTV media center software, such asMythbuntu, a special edition of Ubuntu.

5.7.2 Digital security

Kali Linux is a Debian-based Linux distribution designedfor digital forensics and penetration testing. It comes pre-installed with several software applications for penetra-tion testing and identifying security exploits.[110]

5.7.3 System rescue

Linux Live CD sessions have long been used as a toolfor recovering data from a broken computer system andfor repairing the system. Building upon that idea, sev-eral Linux distributions tailored for this purpose haveemerged, most of which use GParted as a partition editor,with additional data recovery and system repair software:

• GParted Live – a Debian-based distribution devel-oped by the GParted project.

• Parted Magic – a commercial Linux distribution.

• SystemRescueCD – a Gentoo-based distributionwith support for editing Windows registry.

5.7.4 In space

SpaceX uses multiple redundant flight computers in afault-tolerant design in the Falcon 9 rocket. Each Merlinengine is controlled by three voting computers, with twophysical processors per computer that constantly checkeach other’s operation. Linux is not inherently fault-tolerant (no operating system is, as it is a function of thewhole system including the hardware), but the flight com-puter software makes it so for its purpose.[111] For flex-ibility, commercial off-the-shelf parts and system-wide“radiation-tolerant” design are used instead of radiationhardened parts.[111] As of June 2015, SpaceX has made19 launches of the Falcon 9 since 2010, out of which18 have successfully delivered their primary payloadsto Earth orbit, including some support missions for theInternational Space Station.In addition, Windows was used as an operating systemon non-mission critical systems— laptops used on boardthe space station, for example— but it has been replacedwith Linux; the first Linux-powered humanoid robot isalso undergoing in-flight testing.[112]

The Jet Propulsion Laboratory has used Linux for a num-ber of years “to help with projects relating to the con-struction of unmanned space flight and deep space explo-ration"; NASA uses Linux in robotics in the Mars rover,and Ubuntu Linux to “save data from satellites”.[113]

5.7.5 Teaching

Linux distributions have been created to provide hands-on experience with coding and source code to students,on devices such as the Raspberry Pi. In addition to pro-ducing a practical device, the intention is to show students“how things work under the hood”.

6 Market share and uptake

Main article: Linux adoptionSee also: Usage share of operating systems

Many quantitative studies of free/open-source softwarefocus on topics including market share and reliability,with numerous studies specifically examining Linux.[114]

The Linux market is growing rapidly, and the revenue ofservers, desktops, and packaged software running Linuxwas expected to exceed $35.7 billion by 2008.[115] An-alysts and proponents attribute the relative success ofLinux to its security, reliability, low cost, and freedomfrom vendor lock-in.[116][117]

Desktops and laptops According to web server statis-tics, as of March 2015, the estimated market shareof Linux on desktop computers is around 1.5%. Incomparison, Microsoft Windows has a market shareof around 91.5%, while Mac OS covers around7%.[17]

Web servers W3Cook publishes stats that use the topone million Alexa domains,[118] which as of May2015 estimate that 96.55% of web servers runLinux, 1.73% run Windows, and 1.72% runFreeBSD.[119] W3Techs publishes stats that use thetop ten million Alexa domains, which is updated ev-ery month[120] and as of May 2015 estimates that32.6% of web servers run Windows, with the restbeing Linux or Unix.[121] IDC's Q1 2007 report in-dicated that Linux held 12.7% of the overall servermarket at that time;[122] this estimate was based onthe number of Linux servers sold by various compa-nies, and did not include server hardware purchasedseparately that had Linux installed on it later. InSeptember 2008, Microsoft’s CEO Steve Ballmerstated that 60% of web servers ran Linux, versus40% that ran Windows Server.[123]

Mobile devices Android, which is based on the Linuxkernel, has become the dominant operating systemfor smartphones. During the second quarter of2013, 79.3% of smartphones sold worldwide usedAndroid.[92] Android is also a popular operating sys-tem for tablets, being responsible for more than 60%of tablet sales as of 2013.[124] According to webserver statistics, as of December 2014 Android has a

12 7 COPYRIGHT, TRADEMARK, AND NAMING

market share of about 46%, with iOS holding 45%,and the remaining 9% attributed to various nicheplatforms.[125]

Film production For years Linux has been the plat-form of choice in the film industry. The firstmajor film produced on Linux servers was 1997’sTitanic.[126][127] Since then major studios includ-ing DreamWorks Animation, Pixar, Weta Digital,and Industrial Light & Magic have migrated toLinux.[128][129][130] According to the Linux MoviesGroup, more than 95% of the servers and desktopsat large animation and visual effects companies useLinux.[131]

Use in government Linux distributions have alsogained popularity with various local and nationalgovernments. The federal government of Brazilis well known for its support for Linux.[132][133]

News of the Russian military creating its ownLinux distribution has also surfaced, and has cometo fruition as the G.H.ost Project.[134] The Indianstate of Kerala has gone to the extent of mandatingthat all state high schools run Linux on theircomputers.[135][136] China uses Linux exclusivelyas the operating system for its Loongson processorfamily to achieve technology independence.[137]

In Spain, some regions have developed their ownLinux distributions, which are widely used ineducation and official institutions, like gnuLinEx inExtremadura and Guadalinex in Andalusia. Franceand Germany have also taken steps toward theadoption of Linux.[138]

7 Copyright, trademark, and nam-ing

See also: GNU/Linux naming controversy and SCO-Linux controversies

Linux kernel is licensed under the GNU General PublicLicense (GPL), version 2. The GPL requires that any-one who distributes software based on source code underthis license, must make the originating source code (andany modifications) available to the recipient under thesame terms.[139] Other key components of a typical Linuxdistribution are also mainly licensed under the GPL, butthey may use other licenses; many libraries use the GNULesser General Public License (LGPL), a more permis-sive variant of the GPL, and the X.org implementation ofthe X Window System uses the MIT License.Torvalds states that the Linux kernel will not move fromversion 2 of the GPL to version 3.[140][141] He specificallydislikes some provisions in the new license which prohibitthe use of the software in digital rights management.[142]

It would also be impractical to obtain permission from allthe copyright holders, who number in the thousands.[143]

A 2001 study of Red Hat Linux 7.1 found that this distri-bution contained 30 million source lines of code.[144] Us-ing the Constructive Cost Model, the study estimated thatthis distribution required about eight thousand man-yearsof development time. According to the study, if all thissoftware had been developed by conventional proprietarymeans, it would have cost about $1.48 billion (2015 USdollars) to develop in the United States.[144] Most of thesource code (71%) was written in the C programminglanguage, but many other languages were used, includ-ing C++, Lisp, assembly language, Perl, Python, Fortran,and various shell scripting languages. Slightly over half ofall lines of code were licensed under the GPL. The Linuxkernel itself was 2.4 million lines of code, or 8% of thetotal.[144]

In a later study, the same analysis was performedfor Debian version 4.0 (etch, which was released in2007).[145] This distribution contained close to 283 mil-lion source lines of code, and the study estimated that itwould have required about seventy three thousand man-years and cost US$8.16 billion (in 2015 dollars) to de-velop by conventional means.

The name “Linux” is also used for a laundry detergent made bySwiss company Rösch.

In the United States, the name Linux is a trademark reg-istered to Linus Torvalds.[3] Initially, nobody registeredit, but on 15 August 1994, William R. Della Croce, Jr.filed for the trademark Linux, and then demanded royal-ties from Linux distributors. In 1996, Torvalds and someaffected organizations sued him to have the trademark as-signed to Torvalds, and, in 1997, the case was settled.[146]

The licensing of the trademark has since been handledby the Linux Mark Institute. Torvalds has stated that hetrademarked the name only to prevent someone else fromusing it. LMI originally charged a nominal sublicensingfee for use of the Linux name as part of trademarks,[147]

but later changed this in favor of offering a free, perpetualworldwide sublicense.[148]

The Free Software Foundation prefers GNU/Linux as the

13

name when referring to the operating system as a whole,because it considers Linux to be a variant of the GNUoperating system, initiated in 1983 by Richard Stallman,president of the Free Software Foundation.[11][12]

A minority of public figures and software projects otherthan Stallman and the Free Software Foundation, notablyDebian (which had been sponsored by the Free SoftwareFoundation up to 1996[149]), also use GNU/Linux whenreferring to the operating system as a whole.[101][150][151]

Most media and common usage, however, refers to thisfamily of operating systems simply as Linux, as do manylarge Linux distributions (for example, SUSE Linux andRed Hat). As of May 2011, about 8% to 13% of a mod-ern Linux distribution is made of GNU components (therange depending on whether GNOME is considered partof GNU), as determined by counting lines of source codemaking up Ubuntu’s “Natty” release; meanwhile, about9% is taken by the Linux kernel.[152]

8 See also• Comparison of Linux distributions

• Comparison of open source and closed source

• Comparison of operating systems

• Comparison of X Window System desktop environ-ments

• Criticism of Linux

• Linux Documentation Project

• Linux Foundation

• List of Linux distributions

• List of games released on Linux

• List of operating systems

• Loadable kernel module

• Linus Torvalds § Possible NSA approach

• Usage share of operating systems

9 Notes[1] “Linux” trademark is owned by Linus Torvalds[3] and ad-

ministered by the Linux Mark Institute.

10 References[1] Linux Online (2008). “Linux Logos and Mascots”.

Archived from the original on August 15, 2010. RetrievedAugust 11, 2009.

[2] “The Linux Kernel Archives: Frequently asked ques-tions”. kernel.org. September 2, 2014. RetrievedSeptember 4, 2015.

[3] “U.S. Reg No: 1916230”. United States Patent andTrademark Office. Retrieved April 1, 2006.

[4] “Re: How to pronounce Linux?". Newsgroup:comp.os.linux. 23 April 1992. Usenet:1992Apr23.123216.22024@klaava.Helsinki.FI. Re-trieved January 9, 2007.

[5] Free On-Line Dictionary of Computing (June 2006).“Linux”. Retrieved September 15, 2009.

[6] Safalra (14 April 2007). “Pronunciation of 'Linux'".Safalra’s Website. Retrieved September 15, 2009.

[7] “Conflicts between ISO/IEC 9945 (POSIX) and the LinuxStandard Base”. opengroup.org. 2003-07-29. Retrieved2014-04-27.

[8] Eckert, Jason W. (2012). Linux+Guide to Linux Certifica-tion (Third ed.). Boston, Massachusetts: Cengage Learn-ing. p. 33. ISBN 978-1111541538. Retrieved April 14,2013. The shared commonality of the kernel is what de-fines Linux; the differing OSS applications that can inter-act with the common kernel are what differentiate Linuxdistributions.

[9] Linus Benedict Torvalds (5 October 1991). “Freeminix-like kernel sources for 386-AT”. Newsgroup:comp.os.minix. Retrieved September 30, 2011.

[10] “What Is Linux: An Overview of the Linux OperatingSystem”. Linux Foundation. April 3, 2009. RetrievedAugust 15, 2011.

[11] “GNU/Linux FAQ”. Gnu.org. Retrieved 1 September2013.

[12] “Linux and the GNU System”. Gnu.org. Retrieved 1September 2013.

[13] Barry Levine (26 August 2013). “Linux' 22th [sic] Birth-day Is Commemorated - Subtly - by Creator”. SimplerMedia Group, Inc. Retrieved 10 May 2015. Originallydeveloped for Intel x86-based PCs, Torvalds’ “hobby” hasnow been released for more hardware platforms than anyother OS in history.

[14] "NetMarketShare:Mobile/Tablet Operating System Mar-ket Share”.

[15] Computerworld, Patrick Thibodeau. “IBM’s newestmainframe is all Linux”. Retrieved February 22, 2009.

[16] Lyons, Daniel (March 15, 2005). “Linux rules supercom-puters”. Forbes. Retrieved February 22, 2007.

[17] “Desktop Operating System Market Share”. Netmarket-share.com. Retrieved March 15, 2015.

[18] Steven J. Vaughan-Nichols. “Chromebook shipments leapby 67 percent”. ZDNet. Retrieved September 29, 2015.

[19] Linux Devices (January 2010). “Trolltech rolls “com-plete” Linux smartphone stack”. Archived from the orig-inal on 2012-05-25. Retrieved September 29, 2009.

14 10 REFERENCES

[20] “Sony Open Source Code Distribution Service”. SonyElectronics. Retrieved October 8, 2011.

[21] “Sharp Liquid Crystal Television Instruction Manual”(PDF). Sharp Electronics. p. 24. Retrieved October 8,2011.

[22] IBM (October 2001). “Linux Watch (WatchPad)". Re-trieved June 18, 2015.

[23] Ritchie, D.M. (October 1984), “The UNIX System: TheEvolution of the UNIX Time-sharing System”,AT&TBellLaboratories Technical Journal 63 (8): 1577, However,UNIX was born in 1969 ...

[24] “Origins and History of Unix, 1969–1995”. Faqs.org. Re-trieved November 9, 2010.

[25] “About the GNU Project – Initial Announcement”.Gnu.org. 23 June 2008. Retrieved March 9, 2009.

[26] “Overview of the GNU System”. Gnu.org. RetrievedMarch 9, 2009.

[27] “Linus vs. Tanenbaum debate”. Archived from the origi-nal on 2012-10-03. Retrieved February 19, 2014.

[28] Linksvayer, Mike (1993). “The Choice of a GNU Gener-ation – An Interview With Linus Torvalds”. Meta maga-zine. Retrieved January 20, 2009.

[29] “MINIX is now available under the BSD license”, April 9,2000, minix1.woodhull.com

[30] Torvalds, Linus. “What would you like to see mostin minix?". Newsgroup: comp.os.minix. Usenet:1991Aug25.205708.9541@klaava.Helsinki.FI. Re-trieved September 9, 2006.

[31] Linus Torvalds (14 October 1992). “Chicken andegg: How was the first linux gcc binary cre-ated??". Newsgroup: comp.os.minix. Usenet:1992Oct12.100843.26287@klaava.Helsinki.FI. Re-trieved August 17, 2013.

[32] Torvalds, Linus (5 January 1992). “Release notes forLinux v0.12”. Linux Kernel Archives. Retrieved July 23,2007. The Linux copyright will change: I've had a coupleof requests to make it compatible with the GNU copyleft,removing the “you may not distribute it for money” con-dition. I agree. I propose that the copyright be changedso that it confirms to GNU ─ pending approval of thepersons who have helped write code. I assume this is go-ing to be no problem for anybody: If you have grievances(“I wrote that code assuming the copyright would stay thesame”) mail me. Otherwise The GNU copyleft takes ef-fect since the first of February. If you do not know the gistof the GNU copyright ─ read it.

[33] Torvalds, Linus and David Diamond, Just for Fun: TheStory of an Accidental Revolutionary, 2001, ISBN 0-06-662072-4

[34] Torvalds, Linus (March 1994). “Index of/pub/linux/kernel/SillySounds”. Retrieved 2009-08-03.

[35] Garfinkel, Simson; Spafford, Gene; Schwartz, Alan(2003). Practical UNIX and Internet Security. O'Reilly.p. 21.

[36] Santhanam, Anand; Vishal Kulkarni (1 March 2002).“Linux system development on an embedded device”. De-veloperWorks. IBM. Retrieved July 26, 2007.

[37] Schrecker, Michael. “Turn on Web Interactivity withLAMP”.

[38] Galli, Peter (8 August 2007). “Vista Aiding Linux Desk-top, Strategist Says”. eWEEK (Ziff Davis Enterprise Inc.).Retrieved November 19, 2007.

[39] Paul, Ryan (3 September 2007). “Linux market share setto surpass Win 98, OS X still ahead of Vista”. Ars Tech-nica (Ars Technica, LLC). Retrieved November 19, 2007.

[40] Beer, Stan (23 January 2007). “Vista to play second fiddleto XP until 2009: Gartner”. iTWire (iTWire). RetrievedNovember 19, 2007.

[41] “Operating System Marketshare for Year 2007”. MarketShare. Net Applications. 19 November 2007. RetrievedNovember 19, 2007.

[42] “Vista slowly continues its growth; Linux more aggres-sive than Mac OS during the summer”. XiTiMonitor(AT Internet/XiTi.com). 24 September 2007. RetrievedNovember 19, 2007.

[43] “Global Web Stats”. W3Counter. Awio Web ServicesLLC. 10 November 2007. Retrieved November 19, 2007.

[44] “June 2004 Zeitgeist”. Google Press Center. Google Inc.12 August 2004. Retrieved November 19, 2007.

[45] McMillan, Robert. “IBM, Brazilian government launchLinux effort”. www.infoworld.com. IDG News Service.Retrieved 16 February 2015.

[46] “The Linux Foundation; Staff”. Retrieved November 10,2011.

[47] “The Free Software Foundation Management”. RetrievedNovember 10, 2011.

[48] “Free software is a matter of liberty, not price — FreeSoftware Foundation — working together for free soft-ware”. Fsf.org. Retrieved July 12, 2012.

[49] “Why is Linux called a monolithic kernel?". stackover-flow.com. 2009. Retrieved October 16, 2013.

[50] “Anatomy of a Linux System” (PDF). O'Reilly. 2001.Retrieved October 16, 2013.

[51] “Mir: Welcome to Mir”. The leading OS for PC, tablet,phone and cloud | Ubuntu. Canonical Ltd. 10 October2014. Retrieved 11 October 2014.

[52] M. Tim Jones (2006-05-31). “Inside the Linux boot pro-cess”. IBM Developer Works. Retrieved October 16,2013.

[53] “Bash homepage”. GNU Project. Retrieved 29 July 2014.

15

[54] Jake Edge (8 June 2013). “The Wayland Situation: FactsAbout X vs. Wayland (Phoronix)". LWN.net. Retrieved11 October 2013.

[55] “Linux TV: Television with Linux”. linuxtv.org. Re-trieved October 16, 2013.

[56] Jonathan Corbet (2006-10-11). “The Video4Linux2 API:an introduction”. LWN.net. Retrieved October 16, 2013.

[57] “Part I. Video for Linux Two API Specification”. Chapter7. Changes. linuxtv.org. Retrieved October 16, 2013.

[58] Operating System Market Share (November 2009).“Operating System Market Share”. Retrieved December11, 2009.

[59] “POSIX.1 (FIPS 151-2) Certification”.

[60] “How source code compatible is Debian with other Unixsystems?". Debian FAQ. the Debian project.

[61] Eissfeldt, Heiko (1 August 1996). “Certifying Linux”.Linux Journal.

[62] “The Debian GNU/Linux FAQ – Compatibility issues”.Retrieved September 17, 2011.

[63] Linux Format. “Linux Format DVD contents”. Archivedfrom the original on 7 August 2007. Retrieved January17, 2008.

[64] linux-magazine.com. “Current Issue”. Retrieved January17, 2008.

[65] “75% of Linux code now written by paid developers”.APC. Retrieved January 22, 2010.

[66] Brockmeier, Joe. “A survey of Linux Web developmenttools”. Retrieved December 16, 2006.

[67] Advani, Prakash (8 February 2004). “If I could re-writeLinux”. freeos.com. Retrieved January 23, 2007.

[68] Bruce Byfield (August 14, 2007). “Is my hardware Linux-compatible? Find out here”. Linux.com. RetrievedSeptember 4, 2015.

[69] “The LWN.net Linux Distribution List”. LWN.net. Re-trieved March 18, 2015.

[70] What is Linux. Archived at Wayback Engine. Retrieved26 August 2013.

[71] Nathan Willis (2013-08-14). “Prompt-free security forGNOME”. LWN.net. Retrieved November 14, 2013.

[72] “Why I quit: kernel developer Con Kolivas”. APC Maga-zine. ACP Magazines. 24 July 2007. Archived from theoriginal on 2011-07-07. Retrieved August 15, 2011.

[73] “Wayland Architecture”. freedesktop.org. Retrieved Jan-uary 5, 2013.

[74] “The Global Desktop Project, Building Technology andCommunities”. Retrieved May 7, 2006.

[75] Dawe, Liam (2013-01-01). “A 2012 review and what’s instore for 2013?". GamingOnLinux. Retrieved January 2,2013.

[76] Kegel, Dan (14 February 2008). “Google’s support forWine in 2007”. wine-devel (Mailing list). Retrieved Jan-uary 3, 2009.

[77] “Open Source Patches: Wine”. Google. RetrievedSeptember 7, 2008.

[78] Advani, Prakash (27 October 2000). “Microsoft Officefor Linux?". FreeOS. FreeOS Technologies (I) Pvt. Ltd.Retrieved February 3, 2008.

[79] Smith-Heisters, Ian (11 October 2005). “Editing audioin Linux”. Ars Technica. Ars Technica, LLC. RetrievedFebruary 3, 2008.

[80] Lumma, Carl (April 2007). “Linux: It’s Not Just ForComputer Geeks Anymore”. Keyboard Magazine. NewBay Media, LLC. Retrieved February 3, 2008.

[81] James, Daniel (February 2004). “Using Linux ForRecording & Mastering”. Sound On Sound. SOS Pub-lications Group. Retrieved February 3, 2008.

[82] Schofield, Jack (28 May 2009). “Are netbooks losing theirshine?". TheGuardian (London). Retrieved June 2, 2010.

[83] “Introducing the Google Chrome OS”. Official GoogleBlog. Blogger. 7 July 2009. Retrieved 12 June 2014.

[84] Stein, Scott (11 May 2011). “First Take: Samsung Se-ries 5 Chromebook, the future of Netbooks?". Journal(CNET). Retrieved 12 June 2014.

[85] “Rackspace Most Reliable Hoster in September”.Netcraft. 7 October 2006. Retrieved November 1, 2006.

[86] “Aplus.Net is the Most Reliable Hosting Company Site inJune 2008”. Netcraft. 7 July 2008. Retrieved July 28,2008.

[87] “Most Reliable Hosting Company Sites in February2010”. Netcraft. 1 March 2010. Retrieved March 23,2010.

[88] SecuritySpace (1 June 2010). “Web Server Survey”. Se-curitySpace. Retrieved June 27, 2010.

[89] Timothy Prickett Morgan (11 December 2009). “IBMpunts Linux-only mainframes Big MIPS, deep discounts”.The Register. Retrieved July 2, 2009.

[90] “TOP500 Supercomputer Sites: Operating system Family/ Linux”. Top500.org. Retrieved 14 November 2014.

[91] “Sublist Generator”. Top500.org. Retrieved November2014.

[92] “Android Nears 80% Market Share In Global SmartphoneShipments, As iOS And BlackBerry Share Slides, PerIDC”.

[93] “Chapter 3 - maemo Platform Overview”. Wayback Ma-chine. Archived from the original on 2008-06-16. Re-trieved 12 June 2012.

[94] Grabham, Dan (15 February 2010). “Inter and Nokiamerge Moblin and Maemo to form MeeGo”. Retrieved12 June 2014.

16 10 REFERENCES

[95] Whitwam, Ryan (22 February 2014). “Samsung An-nounces Gear 2 and Gear 2 Neo Smart Watches RunningTizen, Available Worldwide In April”. Retrieved 12 June2014.

[96] Gibbs, Samuel (2 June 2014). “Samsung Z smartphoneditches Android for Tizen software”. Retrieved 12 June2014.

[97] “Mer Project”. Mer Project. Retrieved 12 June 2014.

[98] “Firefox OS architecture”. Mozilla Developer Network.Mozilla. Retrieved 13 June 2014.

[99] “App ecosystem”. Ubuntu. Canonical Ltd. Retrieved 13June 2014.

[100] “Tesla Model S Ethernet Network Explored”.

[101] “TiVo ─ GNU/Linux Source Code”. Archived from theoriginal on 19 May 2007. Retrieved December 12, 2006.

[102] “Case Study: How MontaVista Linux helped Yamaha de-velopers make a great product greater” (PDF). Archivedfrom the original (PDF) on 25 September 2007. RetrievedAugust 26, 2007.

[103] “Embedded Linux: FlyingPigs the WholeHogIII runs onLinux”.

[104] Cifaldi, Frank (14 February 2013). “Steam Box phase onecomplete: Steam’s Linux client is out now”. Retrieved 12June 2014.

[105] Larabel, Michael (5 June 2014). “There’s Now 500Games On Steam For Linux”. Journal (Phoronix). Re-trieved 12 June 2014.

[106] “SteamOS”. Steam. Valve. Retrieved 12 June 2014.

[107] Larabel, Michael (16 January 2014). “Valve’s VOGLOpenGL Debugger Should Be Great”. Journal(Phoronix). Retrieved 12 June 2014.

[108] Mattas, Jeff (25 April 2012). “Steam and Source Enginebeing ported to Linux”. Retrieved 13 June 2014.

[109] Buckley, Sean (21 July 2014). “NVIDIA Shield”.Engadget. Retrieved 13 June 2014.

[110] “What is Kali Linux?". Kali Linux. Retrieved 13 June2014.

[111] Svitak, Amy (2012-11-18). “Dragon’s “Radiation-Tolerant” Design”. Aviation Week. Archived from theoriginal on 2013-12-03. Retrieved 2012-11-22.

[112] Steven J. Vaughan-Nichols (May 6, 2013). “To the spacestation and beyond with Linux”. Retrieved 14 November2014.

[113] “Five Ways NASA is Using Linux OS to Run its SpaceProgram”. Retrieved 14 November 2014.

[114] Wheeler, David A. “Why Open Source Software/FreeSoftware (OSS/FS)? Look at the Numbers!". RetrievedApril 1, 2006.

[115] “Linux To Ring Up $35 Billion By 2008”. Retrieved April1, 2006.

[116] “The rise and rise of Linux”. Computer Associates Inter-national. 10 October 2005. Archived from the original on2007-02-17.

[117] Jeffrey S. Smith. “Why customers are flocking to Linux”.IBM. Archived from the original on 2008-06-03.

[118] “W3Cook FAQ”. W3Cook.com. Retrieved 30 June 2015.

[119] “OS Market Share and Usage Trends”. W3Cook.com. Re-trieved 30 June 2015.

[120] “Technologies Overview - methodology infomation”.W3Techs.com. Retrieved 30 June 2015.

[121] “Usage of operating systems for websites”. W3Techs.com.Retrieved 30 June 2015.

[122] "─ IDC Q1 2007 report”. Linux-watch.com. 29 May2007. Retrieved March 9, 2009.

[123] Niccolai, James (September 2008). “Ballmer Still Search-ing for an Answer to Google”. Retrieved June 4, 2009.

[124] Egham (3 March 2014). “Gartner Says Worldwide TabletSales Grew 68 Percent in 2013, With Android Capturing62 Percent of the Market”. Retrieved 13 June 2014.

[125] “Mobile/Tablet Operating System Market Share”. Net-marketshare.com. Retrieved 7 December 2014.

[126] Strauss, Daryll. “Linux Helps Bring Titanic to Life”. Re-trieved July 28, 2011.

[127] Rowe, Robin. “Linux and Star Trek”. Retrieved July 28,2011.

[128] “Industry of Change: Linux Storms Hollywood”. Re-trieved March 11, 2009.

[129] “Tux with Shades, Linux in Hollywood”. RetrievedMarch 11, 2009.

[130] “Weta Digital – Jobs”. Retrieved November 17, 2010.

[131] “LinuxMovies.org – Advancing Linux Motion PictureTechnology”. Retrieved March 16, 2012.

[132] “Brazil’s love of Linux”. Retrieved February 21, 2009.

[133] Ashurst, Mark (1 February 2004). “Brazil falls in lovewith Linux”. BBC News. Retrieved February 21, 2009.

[134] “LV: Minister: “Open standards improve efficiency andtransparency"". Retrieved February 21, 2009.

[135] “Linux Spreads its Wings in India”. Retrieved February21, 2009.

[136] “Kerala shuts windows, schools to use only Linux”. Re-trieved June 22, 2009.

[137] “China’s Microprocessor Dilemma”. Microprocessor Re-port. Retrieved April 15, 2009.

[138] Krane, Jim (30 November 2001). “Some countries arechoosing Linux systems over Microsoft”. Seattle Post-Intelligencer. Retrieved February 21, 2009.

[139] “GNU General Public License, version 2”. GNU Project.1991-06-02. Retrieved December 5, 2013.

17

[140] Torvalds, Linus (26 January 2006). “Re: GPL V3 andLinux ─ Dead Copyright Holders”. Linux Kernel MailingList.

[141] Torvalds, Linus (25 September 2006). “Re: GPLv3 Posi-tion Statement”. Linux Kernel Mailing List.

[142] Brett Smith (2013-07-29). “Neutralizing Laws That Pro-hibit Free Software — But Not Forbidding DRM”. AQuick Guide to GPLv3. GNU Project. Retrieved Decem-ber 5, 2013.

[143] “Keeping an Eye on the Penguin”. Linux-watch.com. 7February 2006. Retrieved November 9, 2010.

[144] Wheeler, David A (29 July 2002). “More Than a Giga-buck: Estimating GNU/Linux’s Size”. Retrieved May 11,2006.

[145] Amor, Juan José; et al. (17 June 2007). “Measuring Etch:the size of Debian 4.0”. Retrieved September 16, 2007.

[146] “Linux Timeline”. Linux Journal. 31 May 2006.

[147] Neil McAllister (5 September 2005). “Linus gets toughon Linux trademark”. InfoWorld. Retrieved February 24,2008.

[148] “Linux Mark Institute”. Retrieved February 24, 2008.LMI has restructured its sublicensing program. Our newsublicense agreement is: Free – approved sublicense hold-ers pay no fees; Perpetual – sublicense terminates only inbreach of the agreement or when your organization ceasesto use its mark; Worldwide – one sublicense covers youruse of the mark anywhere in the world

[149] Richard Stallman (1996-04-28). “The FSF is no longersponsoring Debian”. tech-insider.org. Retrieved February8, 2014.

[150] “About Debian”. debian.org. 2013-12-08. Retrieved Jan-uary 30, 2014.

[151] Andrew D. Balsa; Coauthors. “The linux-kernel mail-ing list FAQ”. The Linux Kernel Archives. Kernel.org.Archived from the original on 2012-10-01. Retrieved2013-06-13. ...we have tried to use the word “Linux” orthe expression “Linux kernel” to designate the kernel, andGNU/Linux to designate the entire body of GNU/GPL'edOS software,... ...many people forget that the linux ker-nel mailing list is a forum for discussion of kernel-relatedmatters, not GNU/Linux in general...

[152] Côrte-Real, Pedro (31 May 2011). “How much GNU isthere in in GNU/Linux?". Split Perspective. RetrievedJanuary 28, 2014. (self-published data)

11 External links• Linux at DMOZ

• Graphical map of GNU/Linux OS Internals

• Linux kernel website and archives

• Linux.org

• The History of Linux in GIT Repository Format1992–2010

• A list of free Linux distributions, provided by theFree Software Foundation

18 12 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

12 Text and image sources, contributors, and licenses

12.1 Text• Linux Source: https://en.wikipedia.org/wiki/Linux?oldid=684942562 Contributors: Damian Yerrick, AxelBoldt, Magnus Manske, The

Cunctator, Lee Daniel Crocker, Brion VIBBER, Eloquence, Uriyan, Zundark, The Anome, Tarquin, Stephen Gilbert, Koyaanis Qatsi, DavidMerrill, Malcolm Farmer, Ffaker, Amillar, Youssefsan, XJaM, Arvindn, Christian List, Matusz, Phil Bordelon, Fubar Obfusco, MadSur-geon, William Avery, Roadrunner, SolKarma, Shii, Sharuzzaman, Hannes Hirzel, Drbug, Ellmist, Ark~enwiki, Jaknouse, Dwheeler,Modemac, Metz2000, Chuq, Stevertigo, Hfastedge, DennisDaniels, Nevilley, Frecklefoot, Edward, Nealmcb, Ghyll~enwiki, MichaelHardy, Kwertii, JakeVortex, Isomorphic, Dante Alighieri, Ronincyberpunk, Norm, Nixdorf, Collabi, Wwwwolf, Wapcaplet, Ixfd64,Bcrowell, Gaurav, Graue, Dcljr, Sannse, Tomi, TakuyaMurata, Delirium, Skysmith, (, 7265, Minesweeper, Pagingmrherman, CesarB,Egil, Mdebets, Ahoerstemeier, TomK32, Haakon, Mac, Stevenj, Nanshu, Baylink, Theresa knott, Snoyes, CatherineMunro, 5ko, An-gela, Den fjättrade ankan~enwiki, Jebba, LittleDan, Julesd, Salsa Shark, Ugen64, Glenn, Kvintadena, Acooley, Whkoh, AugPi, Nikai,Susurrus, Cimon Avaro, Kaihsu, Shammack, Evercat, Jordi Burguet Castell, Rl, Darkonc, Dwo, Hashar, Coren, Barak~enwiki, Tarka,Emperorbma, Crusadeonilliteracy, Guaka, Timwi, Dcoetzee, Nohat, Andrevan, RickK, Dmsar, Ww, Mac c, Slathering, Sepper, Paul Stan-sifer, Dysprosia, Hydnjo, Jay, Enigmasoldier, Zoicon5, Hdk, DJ Clayworth, CBDunkerson, Lotas, Halmonster, Maximus Rex, JeffreySmith, Grendelkhan, Morwen, Saltine, Wwheeler, Populus, Fibonacci, Omegatron, Ed g2s, Ann O'nyme, Wernher, Samsara, Thue, Bevo,Traroth, Topbanana, Earthsound, Joy, Fvw, Stormie, Raul654, AnonMoos, Baffclan, Chrisjj, Pakaran, Jusjih, Johnleemk, Flockmeal,D8uv, Anjouli, Guppy, Finlay McWalter, Francs2000, Aenar, Chuunen Baka, AlexPlank, Robbot, Pfortuny, Ke4roh, Chealer, Noldoaran,Wanion, Sander123, Astronautics~enwiki, Fredrik, Kizor, Chris 73, R3m0t, Vespristiano, RedWolf, Dittaeva, Klanda, Romanm, Nbarr,Phatsphere, Tim Ivorson, Markcollinsx, Mirv, Stewartadcock, Wjhonson, Merovingian, Pingveno, Ashdurbat, RossA, Henrygb, Clngre,Rursus, Texture, Meelar, Ckorff, Jondel, Paul G, Hadal, Dehumanizer, JesseW, Victor, Cbm, Ianml, Michael Snow, Fuelbottle, Mushroom,Boarder8925, Isopropyl, Diberri, Mattflaschen, Pengo, Dina, Tobias Bergemann, Mlk, Alan Liefting, David Gerard, Cedars, Psb777, Cen-trx, Giftlite, Julianp, Mshonle~enwiki, DavidCary, Elf, Sj, Jtg, Axeman, Nichalp, Markvs, Massysett, Tobiah, Kenny sh, Ævar ArnfjörðBjarmason, Netoholic, Lethe, Tom harrison, Lupin, Tubular, Herbee, Dissident, Neuro, Bradeos Graphon, Jonabbey, Curps, NeoJustin,Michael Devore, Nomad~enwiki, Jfdwolff, Sdfisher, RatOmeter, Maroux, Energiza, Guanaco, Masken, Daniel Brockman, Alan Chang,Sinclair44, AlistairMcMillan, Gugilymugily, Cjensen, Darrien, Jaan513, MikaelSorlin, Python eggs, Alvestrand, Pne, Lakefall~enwiki,Bobblewik, AlanCox, Mobius, Ryanaxp, Peter Ellis, Utcursch, SoWhy, Shibboleth, CryptoDerk, Cbraga, SarekOfVulcan, Yath, Yard-cock, Quadell, Emphazy, Antandrus, Demonslave, Onco p53, Joeblakesley, Estel~enwiki, Robert Brockway, Quarl, Melikamp, Bong-bang, Am088, Bonethugnd, Jossi, Wehe, Hackeron, AlexanderWinston, Rdsmith4, MAxImUs ReX, Maximus Rex is a FAGOT!!!, Vbs,Bumm13, Bornslippy, Kbrooks, Daniel11, Halo, Bk0, Goh wz, Sam Hocevar, Talrias, Eanschuessler, Cynical, Stilroc, Troels Arvin, Gsc-shoyru, Gnu~enwiki, Meb, Oknazevad, Imjustmatthew, Goobergunch, Kevin Rector, StephanDoerner, Jiel.B, Now3d, Chmod007, Zondor,Trevor MacInnis, Squash, Intrigue, Moxfyre, Praveer, Grunt, RandalSchwartz, DmitryKo, Jfpierce, Kate, Daxkelson, J.B. Nicholson-Owens, Corti, Ta bu shi da yu, Wanted, Daviis~enwiki, Rfl, Tom X. Tobin, Imroy, Sysy, MM23, Felix Wiemann, Trypa, Discospin-ster, Rich Farmbrough, Rhobite, Guanabot, Sladen, Bedel23, Hydrox, FT2, Invictus~enwiki, Cfailde, Drano, Magic5ball, Rama, Jpk,Iswm, Andrewferrier, Zen-master, Wk muriithi, EliasAlucard, Smyth, Will2k, Mjpieters, Michael Zimmermann, Paul August, Gronky,Stereotek, Shlomif, Lachatdelarue, Bender235, ESkog, Rokcathang, Moa3333, Kbh3rd, Dcabrilo, Kjoonlee, Kaisershatner, Elykyllek,Plugwash, BACbKA, Elwikipedista~enwiki, Evice, PlasmaDragon, RobyWiki~enwiki, CanisRufus, Kop, Pt, Shad0, Kiand, Miraceti,Kloy1334, Kwamikagami, Mwanner, Richard W.M. Jones, Tverbeek, Jantangring, Shanes, Spearhead, Mr. Strong Bad, Raidenmaru,Matteh, Pikestaff, Eltomzo, Mqduck, Migozared, Causa sui, Bobo192, Nigelj, Alegna~enwiki, Mike Schwartz, Rhoppenrath, Mrdelayer,StarFucks, John Vandenberg, Ch1pman, RAM, GTubio, Jericho4.0, Spug, ParticleMan, SoulJuice, Scott Ritchie, SpeedyGonsales, Ra-jah, Alexs letterbox, Franl, Jaguar2k, RichardNeill, Minghong, Towel401, Bobby Digital, James Foster, Npc, Obradovic Goran, Idleguy,Sam Korn, Mattl, Sean Kelly, Impro v, Zachlipton, Djspiewak, Rernst, Poweroid, Alansohn, JYolkowski, Onursendag~enwiki, Proteus71,Jamyskis, Sheehan, Fadookie, Njaard, Eric Kvaalen, Conan, Atlant, A.M.~enwiki, Pravs, AzaToth, Yamla, Axl, AeneasMacNeill, Swift,Dkennert, Mysdaao, Mrholybrain, Malo, VladimirKorablin, Ashlux, Wtmitchell, Velella, Ronark, Gbeeker, SidP, Jrleighton, Suruena,Aka, Evil Monkey, 2mcm, Tony Sidaway, Gpvos, Geraldshields11, LFaraone, Zoohouse, Chevelle572, Deadworm222, P Ingerson, Josh-brez, Bestiarosa, Pauli133, Versageek, K3rb, Netkinetic, Voxadam, Btornado, Kbolino, Andyault, Dismas, Bruce89, Oleg Alexandrov,Mahanga, Kmself, Dejvid, INic, Weyes, Xanthar, Evolve75, Kelly Martin, Simetrical, Firsfron, OwenX, Woohookitty, Brazil4Linux,TigerShark, GVOLTT, Jesse Hannah, Timo Laine, LOL, Thorpe, Saragc, Uncle G, Borb, Gherald, Snodnipper, Scott.wheeler, Roblinux,Pages, MattGiuca, Ruud Koot, Dodiad, JeremyA, Mms, Hdante, Tedneeman, Rtdrury, Acerperi, Cy21, Wces423, Bkwillwm, Dmol, Bbat-sell, TreveX, Frungi, El Suizo, Rchamberlain, CharlesC, Waldir, Crucis, Toussaint, Prashanthns, Gimboid13, Wisq, Karam.Anthony.K,Teemu Leisti, Omega21, Turnstep, Havocted, Rgbea, Marudubshinki, LeoO3, LimoWreck, Kesla, Graham87, Cuvtixo, Magister Mathe-maticae, Hillbrand, Ilya, BD2412, Qwertyus, Kbdank71, Lanoitarus, Haikupoet, JIP, Island, Reisio, Jshadias, Stdout, Phoenix-forgotten,Josh Parris, Ryan Norton, Canderson7, Rjwilmsi, Tizio, Koavf, DucoNihilum, Jake Wartenberg, Eddypoon, Buck09, Strait, Mjm1964,Bob A, MarSch, XP1, Quiddity, Linuxbeak, CDCAA18D, JHMM13, Tangotango, Bruce1ee, Fifty, Mitul0520, Gudeldar, Scorchsaber,Ligulem, Boccobrock, Graibeard, Muj0, The wub, Bhadani, Dar-Ape, BirdbrainedPhoenix, FlavrSavr, Jakers3200, Sango123, Svaksha,Yamamoto Ichiro, Austrian, SNIyer12, Leithp, SLi, Titoxd, StuartBrady, RicKk, TrinkerBell, Toresbe, SchuminWeb, Vizion, Lolroxors,Loggie, Ysangkok, Godlord2, Crazycomputers, Harmil, Nivix, Chanting Fox, Soulnoise, Jsheehy, Flowerparty, Superchad, RexNL, Scot-trainey, Intgr, Jagginess, Wingsandsword, ZScout370, Clockwork Soul, Alphachimp, Bmicomp, Greenpenguin~enwiki, Kedadi, Ahunt,Exe, Theshibboleth, Butros, King of Hearts, CStyle, Bornhj, DVdm, Actown, Korg, Bgwhite, Jpkotta, Mysekurity, Gwernol, Tone, Robotode Ajvol, Siddhant, Lunarcloud, Wavelength, Eraserhead1, Sceptre, I need a name, Hairy Dude, Charles Gaudette, Mclayto, StuffOfIn-terest, Adam1213, Simoncpu, BruceDLimber, Hyad, Sakurina, Jtkiefer, John Quincy Adding Machine, The Storm Surfer, Splash, Hen-drixski, Limulus, Gardar Rurak, SpuriousQ, Ansell, Akamad, Dotancohen, Archelon, Gaius Cornelius, Rsrikanth05, Yvovandoorn, Bovi-neone, Pelago, Tarheelcoxn, Draeco, Anomalocaris, Srini81, Antidrugue, Capi, Linuxguy3827, NawlinWiki, Stephen Burnett, Green-lead, Wiki alf, Mipadi, CrackMonster McFuckDemon, Msikma, Ozarfreo, Jaxl, Julien Deveraux, Mkouklis, Barberio, Dureo, Musteval,Saoshyant, Retired username, Aaron Brenneman, PrologFan, Randolf Richardson, ThomasChung, D. F. Schmidt, Jpbowen, Sekelsen-mat, Raven4x4x, Fuck Linux, Dementedd, Off!, Voidxor, Vipsta, Beanyk, Tony1, Aaron Schulz, User-green, Leotohill, Suso, Mysid, Psyguy, MathNT, Jeremy Visser, T-rex, Jhinman, Hosterweis, Elkman, Dan Austin, Mike92591, Wknight94, The Halo, Mugunth Kumar,Rwxrwxrwx, FF2010, Sandstein, Zerathidune, Kenguest, Emijrp, Masatran, KingKane, Zzuuzz, Harrisonmetz, Encephalon, Nfreader,Mike Dillon, Ahmednh, IsUsername, Danudey, Petri Krohn, GraemeL, JoanneB, Kingkiki217, Janizary, Fram, Smurrayinchester, Pe-ter, Kevin, JLaTondre, Gorgan almighty, WormNut, ViperSnake151, Katieh5584, Simxp, Kungfuadam, Camje lemon, DCEvoCE, RG2,Kuzain, Rwwww, Infinity0, Airconswitch, Ajross, Mardus, Arnabbh, Quadpus, Blastwizard, Hal peridol, DrJolo, Sardanaphalus, Sarah,SmackBot, John Lunney, Macorovi, Fireman biff, Sparkyf1, Kbedell, Historian932, Mihai cartoaje, Faisal.akeel, Andras23, Coq Rouge,

12.1 Text 19

Bobet, ThreeDee912, Rtc, State of Love and Trust, InverseHypercube, KnowledgeOfSelf, NaiPiak, Bd84, Lantianer, Pgk, Cutter, Vald,Elsewhere~enwiki, Gary Kirk, Wegesrand, Phaldo, KVDP, Actin, Delldot, Darklock, GeneralAntilles, Kangy, Arny, Tiberious726, Capi-talSasha, Vilerage, Kintetsubuffalo, Kslays, Hbackman, BiT, Lucohami, 42istheanswer, HalfShadow, Flankk, Echimu, Tommstein, Gaff,Jmendez, Xaosflux, Diegotorquemada, 1c3d0g, Unforgettableid, KennethJ, PeterSymonds, Gilliam, Brianski, Ohnoitsjamie, Coplan, Os-carthecat, Richfife, Geronimooo, JorgePeixoto, Ioprwe, Jared0x90, Fetofs, Saros136, Westsider, LinuxDemos, Redk0de, Persian Poet Gal,JDCMAN, Thumperward, Morte, Snori, Rogerhc, Jojo 1, SchfiftyThree, Donnie Love, Akanemoto, Jerome Charles Potts, Imagine1989,Marc321, Wolf0403, Letdorf, Baronnet, Duneatreides, JGXenite, Gyrobo, Modest Genius, Dethme0w, Can't sleep, clown will eat me,Harumphy, 1(), Mohnke, Hildanknight, Frap, Sunnan, Klacquement, Juancnuno, Skidude9950, JonHarder, Adomas, Vegard, MrBobla,Zvar, Jcravens42, Cyber rigger, Edivorce, Rpgdude, Soosed, Krich, Zrulli, Emre D., Spectrogram, Cybercobra, Decltype, MureninC,Makemi, Nakon, Akulkis, Brithackemack, MichaelBillington, Blake-, Chargh, Orbitalwow, Localzuk, Monotonehell, Shadow1, Dread-star, Dave-ros, Marc-André Aßbrock, Warren, Anoriega, Onlinej, Binary2k5, Markhobley, Weregerbil, Seven Days, CristianoMacaluso,Fitzhugh, Wisco, Freedom to share, SpiderJon, Phoenix314, Kotjze, James Mohr, Where, Sigma 7, Gurklurk, Curly Turkey, Pilotguy,Kukini, AnK, Ged UK, Ohconfucius, LN2, Caleb Parks, Liquidtenmillion, Nishkid64, Dr genestealer, ArglebargleIV, Rory096, AThing,Staalmannen, Guyjohnston, Axem Titanium, JzG, HeroTsai, Wtwilson3, Jaganath, Djwings, Sir Nicholas de Mimsy-Porpington, Shadow-lynk, Tim Q. Wells, Zyqwux, CaptainVindaloo, Zarniwoot, Gnevin, MonstaPro, Mr. Lefty, Beefball, EvanR, Intiendes, Thomas Gilling,Ben Moore, Anguis, Plato2006, Aav, Agathoclea, Slakr, Hvn0413, 81120906713, Ems2, Thekittenofterra, SQGibbon, Subiet, Arkrishna,Optakeover, FourDollarsAndFiftyTwoCents, Սահակ, Waggers, Sasabune, Spiel496, Cbruno, Jose77, Peyre, LaMenta3, Thatcher, Galac-tor213, Inquisitus, Galadh, DanConnolly, Liquidat, Hu12, Lucid, Fasach Nua, JYi, Emx~enwiki, Jparshall, Iridescent, Bradojev, Bmuller,Ronius, JoeBot, Thepizzaking, Wiki man sam, Andrew Hampe, Tony Fox, Beno1000, Momet, Courcelles, Linkspamremover, Htmlland,Knirirr, Fdp, Tawkerbot2, Alegoo92, RaviC, Inkybutton, Lahiru k, AdrianTM, SkyWalker, Zealotgi, Ruykava, Nintendomania, Linuxerist,Sakurambo, Gebbun, CRGreathouse, Boborok, Raysonho, Mgumn, Ithuwakaga, Xose.vazquez, CWY2190, MonstrousBone, Tjkiesel, Cu-riousEric, Vbv4, Jaxad0127, Xakuzzah, DanielRigal, Requestion, Lentower, Lyoko is Cool, Avillia, Michael B. Trausch, Tim1988, Karenjc,Skybon, Rmallins, Inzy, Beowulf.1000, Cydebot, Karimarie, Bill (who is cool!), ChristTrekker, Scofield Boy, Asmitford, UncleBubba,Gogo Dodo, Red Director, Ttiotsw, ST47, A Softer Answer, Chasingsol, Huysman, Pascal.Tesson, RitBit, Tawkerbot4, Quibik, Enigmafoundry, HitroMilanese, Msnicki, Codetiger, Nikopoley, Torc2, DumbBOT, Michaelbarnes, Brumar59, Blb9t, Jmartin678, Akcarver,Kozuch, Bsmntbombdood, Neustradamus, AVIosad, Gregvw, Daniel Olsen, Instaurare, Danhm, Epbr123, Barticus88, Mercury~enwiki,FromanylanD, Bytebear, KimDabelsteinPetersen, Edupedro, Cain Mosni, TZM, Sagaciousuk, Frozenport, Jdm64, Mojo Hand, Head-bomb, Hugh G. Rection, Dddelfin, Blkf, James086, Java13690, Mr pand, X201, Turkeyphant, OtterSmith, Dfrg.msc, Aleksanteri, NigelR,TurboForce, Mlogic, Ranunculoid, Big Bird, Kohlrabi, Evmilker, Santoshsnayak, Rtoris288, Dawnseeker2000, Urdutext, CowardX10,AlefZet, Escarbot, Mentifisto, Hmrox, The prophet wizard of the crayon cake, AntiVandalBot, Luna Santin, Widefox, Clarenceville Tro-jan, Guy Macon, Wildboy211, Stephenx77, Prolog, Hectard, Robzz, SmokeyTheCat, DivineOmega, TimVickers, Tmopkisn, Scepia,Isilanes, Bakabaka, Dylan Lake, Coviti, Obsessiveatbest, Mutt Lunker, WChess, LéonTheCleaner, Dmerrill, Neur0X, Ioeth, JAnDbot,Deflective, Kigali1, Aibara, Kaobear, DuncanHill, Skridge, NapoliRoma, Barek, Dustin gayler, MER-C, Lino Mastrodomenico, Archdude, Fetchcomms, Jephir, THEBLITZ1, Nickvikeras, Reverendnathan, ANTROPOCENTRIO, Amcleodx, Jpolster2005, Danwri, Al-liance1911, Acroterion, SteveSims, I80and, Plamoa, Joebengo, Caronteycerbero~enwiki, Magioladitis, Chevy20Man, Canjth, Bongwar-rior, VoABot II, Kamran Riaz Khan, Rhwawn, LOLDSFAN, Wikidudeman, Hasek is the best, JNW, JamesBWatson, Marko75, JéskéCouriano, Stuart Morrow, Tedickey, Jancikotuc, Twsx, Loqi, Rootxploit, Aka042, Avicennasis, JMBryant, Trapped2, Indon, PanserBorn, Troykitch, 28421u2232nfenfcenc, Ciaccona, Sirsai, Allstarecho, LorenzoB, Zaid85, OpenAdvantage, Bugtrio, Alansing, Xavierorr,TehBrandon, Chris G, DerHexer, Esanchez7587, Nankai, ChaosE, Pax:Vobiscum, Patstuart, Calltech, Fluteflute, Wikinger, Pikolas, Mur-raypaul, Gwern, Aliendude5300, S3000, AVRS, Jerem43, Etinin, Conquerist, MartinBot, LiamUK, Pádraig Coogan, EyeSerene, Bet-Bot~enwiki, Janolder, Arjun01, Faazshift, Aladdin Sane, Draconicus, Rettetast, Paunaro, Trevorp, Filksinger, Peco4, Dominic7848, R'n'B,CommonsDelinker, KTo288, Fattymcbluff, Senthryl, TinaSDCE, LouDogg, TLF1981, Leson2403, Slash, Exarion, J.delanoy, Priscill-aBerry, Trusilver, Lord Samael, Deep Alexander, Kulshrax, Uncle Dick, Public Menace, Lonjers, Man123123, Jascha00, NerdyNSK,Footballfan42892, Cpiral, Arite, WikiTorch, Barts1a, Bogods, Dispenser, Katalaveno, Firedraikke, McSly, Nemo bis, Ignatzmice, Gross-cha, Crakkpot, Starnestommy, Touisiau, SUOERMAX, NiGHTS into Dreams..., AntiSpamBot, RoboMaxCyberSem, Shaka908, NewEng-landYankee, Gelasius, Diego.viola, MKoltnow, Mufka, Rekiwi, Memmke, Orrs, BigHairRef, Mocoloco311, 2help, Bob, Cometstyles,Jamesontai, Remember the dot, GregJackP, Gwen Gale, Uluboz, Ilya Voyager, Phiv, Natl1, Rugby471, Bonadea, Nat682, Starnessonny,PowerSp00n, Xlunchboxtbx, Czarbender, Belegur, Jarry1250, Chris Pickett, HighKing, Raunaak, Mark the ma3, Butholer, Rémih, Ste03,Idioma-bot, Spellcast, Davidr89, Sagar bhatia26, Nomaxxx, Omglinuxrulez, Jyoungxxxx, Fultus, VolkovBot, Jrasmuss, Jeff G., Indu-bitably, Alexandria, Cadby Waydell Bainbrydge, Lear’s Fool, Philip Trueman, Fran Rogers, TXiKiBoT, WatchAndObserve, Jkstark,Raty2hotty, Tagno25, Shne, Ensign Q, Couilles007, Eastoff, Comrade Graham, Technopat, A4bot, Xerxesnine, GDonato, MrFirewall,Qxz, DaBest1, DFSwiki, Seraphim, Pikidalto, Martin451, Virtual11234, Nibsthomas, Leafyplant, Jackfork, LeaveSleaves, Sgbirch, Josepy,Tb33, Ilyushka88, Thomas419ca, Merctio, TJollans, ShedPlant, Craiggyb, Nonsequitor, Andy Dingley, Dougbertram, Henrysukumar,Dirkbb, Rbuicki, Meters, Lamro, Synthebot, Altermike, Prestondocks, Tomaxer, Enviroboy, EleFlameMax, Kalan, Chachy18, AlanS,Fr0dofraggins, The Devil’s Advocate, Nibios, Brianga, Treyfury, Monty845, HiDrNick, Twooars, Shdw.puppet, Michelleem, Thunder-bird2, Logan, Darxus, Jeremiah Griffin, Slidexd, EmxBot, Arne Brasseur, RedChinaForever, H92, Kbrose, Diah ayu, The Random Editor,Biscuittin, Qwertydvorak, Ewewfws, Wumingzi, Terryjones130, SieBot, TJRC, Dusti, Anhimgr8, Milnivri, Scatteredpixels, 0bj3c7i0n,Psbsub, Fanra, Blusme1, Krawi, Josh the Nerd, H.7004.Vx, Parhamr, Dawn Bard, Caltas, RJaguar3, Swaq, Radof94, Yintan, I LovePi, ThomasJensenDaugaard, Boxxertrumps, Mr. Maka, Martinsanders, Mrmister001, Thejackisback, Pitilessbronze, Ham Pastrami, Jer-ryobject, Purbo T, Krishna.91, Cjayakumar, PookeyMaster, Acet0ne, Mattkicksbottomnomsayin, Android Mouse, Flyer22, Tiptoety,Radon210, Exert, Moosemanx, Momo san, Nopetro, Askild, Hiddenfromview, Narkou, Carazo~enwiki, Chemtype, Nslater, Oxymoron83,Majojohnson, Harry~enwiki, Shayolar, Poindexter Propellerhead, KathrynLybarger, Nicuro, Hobartimus, Astrale01, Iamnotyouami, Mill-stream3, Macy, Hatster301, Jorgen W, Pascal Steger, Nancy, KritonK, Svick, Maelgwnbot, Aa00076765aa, Rkarlsba, Soleedges, Red-Blade7, Kentynet, Openiworld, Tcrow777, Maralia, Sapeli, Ascidian, Haris.tv, Dabomb87, Treekids, Baosheng, Jean pierreCamu5, Iccdel,Kanonkas, TuxDistro, PsyberS, Tuntable, StewartMH, Tranalogic~enwiki, Dav7, Missing Ace, Smashville, Martarius, Rfvuhbtg, ClueBot,Mapiwef, Smart Viral, Kevanv, Binksternet, GrandDrake, The Thing That Should Not Be, Aohara1986, Number774, Freed42, Imper-fectlyInformed, Homelessboxman, Ryannelson714, Czarkoff, Arakunem, Rockonbon, Kl4m-AWB, Der Golem, Jamie Bates, Perkster,Wwood28, Alvarokr, Wikijens, CounterVandalismBot, Blanchardb, Mhmondragon 1, Tnchris, Ramif 47, Melizg, Carsoman, Chmpoure,Bald Eeagle, NotSuspicious, DragonBot, Damon S Lucas, Awickert, Excirial, Propeng, Bproffitt, Alexbot, Kanguole, Tuxthepenguin933,Eeekster, Vivio Testarossa, Lightedbulb, Lartoven, Technobadger, Cenarium, Nikesh.jauhari, Jotterbot, WalterGR, Barretboy, Rcsteve93,Dekisugi, Tempmj, Noxia, SchreiberBike, Mewtu, DanielPharos, Bald Zebra, Sdrtirs, Andy16666, TomoFR, Error −128, Gremoldo,Aitias, Count Truthstein, Scalhotrod, Wmadavis, Versus22, GameSlaveX-13, Callinus, Multikty~enwiki, SoxBot III, Somekindofuser-name, W4otn, SF007, Valdis.vitolins, DumZiBoT, Templarion, Steveozone, Chris1834, Hogman500, XLinkBot, Blaznspadz, Fleeson,

20 12 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

Aaron north, Fastily, Ptfbending, Koolabsol, Xray7224, Marriottn, PseudoOne, SakJur, Estemi, Rror, Bradv, Dthomsen8, Btvideo, Leoro-jas82, Little Mountain 5, Klungel, SilvonenBot, Olegthezenon, Gazimoff, Bit Lordy, Soulzone, Zodon, Dwilso, Ryuinfinity, RyanCross,Dsimic, Gggh, Kgoetz, Kodster, Dr. Robotnic, Tayste, Addbot, Proofreader77, Man with one red shoe, Pyfan, Archerman2000, Grayfell,LPfi, Some jerk on the Internet, Titanramones, Msanguino, Tcncv, Okoura, Thomas888b, AlbinoFerret, Superw4w, Xicer14, Tothwolf,Grandscribe, Fieldday-sunday, Hoax99, Scientus, CanadianLinuxUser, ThinkMark, Leszek Jańczuk, GrrlPower, Jcgrob, Thunderpen-guin, Laskdfj456, Michael2346, Pclunixos, Debresser, LinkFA-Bot, Jasper Deng, Jake7401, Fireaxe888, Tsange, Peter Napkin DanceParty, AgadaUrbanit, Darkanimematt, Irvanis, Numbo3-bot, Danutzdobrescu, Issyl0, R3ap3R, Tide rolls, Lightbot, Club5566~enwiki,Gail, Zorrobot, Jarble, Felisone, CountryBot, Team4Technologies, Blablablob, Yobot, CFeyecare, Legobot II, Darfellan, Ogredeschnique,DeluxNate, Mirosamek, Golftheman, QueenCake, Luizdl, Jerebin, Kailasisonline, Davidjohn1969, Knownot, Punctilius, Nightfire001,Xeku~enwiki, Steveux, Spammer64, South Bay, Tempodivalse, Magog the Ogre, Szajci, AnomieBOT, KDS4444, 1exec1, Götz, In-cidentalPoint, Rjanag, Jose278, Royote, Keithbob, AdjustShift, Earizon, Flewis, Aaron dub, Mann jess, Frebel93, Skkamath, Materi-alscientist, Kr0n05931, The High Fin Sperm Whale, Citation bot, Carlsotr, Maxis ftw, Kellogg257~enwiki, Neurolysis, ArthurBot, Que-bec99, Diddy29, The Firewall, MauritsBot, Xqbot, ChicagoDilettante, Timir2, Capricorn42, Y.P.Y, CoolingGibbon, 4twenty42o, Miracle-worker5263, Smk65536, Foxcow, Person1936, Teddks, Alaaanwar, Wiki-Saboteur, Anna Frodesiak, Locos epraix, Someslowly, Taruean,GRAPEMAPLESYREP, Shadowrpg, Hi878, Noscope101, Jamie Bunting, Homyakchik, Socaltechboy, Shirik, Uniwersalista, RibotBOT,SassoBot, Kernel.package, Dalesc, Amaury, WilliamTheaker, Kpm0310, Doulos Christos, AlasdairEdits, GhalyBot, Minorworlder, 2ndAc-count, Shadowjams, Tuxman, KFV101, Milanix, Josemanimala, Hiimluke, Dougofborg, Swatnio~enwiki, Cachorro Podre, Texasranger9,Vlad003, FrescoBot, 0imagination, Lagelspeil, IvarTJ, W Nowicki, Mhadi.afrasiabi, Srbobranac, Aperson5654236, Gaddarca, HJ Mitchell,L1ttleTr33, Mynam690, Tetraedycal, Grohlerg, Nobodys Fool, DivineAlpha, HamburgerRadio, Pinged007, Pshent, Busukxuan, SimpleBob, Viralmeme, WQUlrich, Pinethicket, I dream of horses, Farazv, Bolatan, Tóraí, 10metreh, Jonesey95, Martin Raybourne, Smuckola,Skyerise, Boston rider, BRUTE, RedBot, Houbysoft, 124Nick, SpaceFlight89, Jeliekbigbusanas, Σ, Doppelback, Jandalhandler, Footwar-rior, Woona, Lineslarge, Full-date unlinking bot, ZxPezz, Travisman26, Wenet~enwiki, PixelRGB, Herakleitoszefesu, Dinmammaerfet,FoxBot, TobeBot, Diblidabliduu, Econtechie, Lexischemen~enwiki, Yunshui, Wolfehhgg, DicksForSale, André Caldas, Bendib, Lotje,Michael9422, Zvn, SeoMac, Iamsocool97, Drknkn, Aoidh, Saneeth.pr, David Hedlund, Diannaa, Ivanvector, Sniperdude0, Jimb0onwheelz,Knightmeepo, Lysander89, Sandhiav, Suffusion of Yellow, Nascar1996, Tbhotch, Jesse V., DARTH SIDIOUS 2, PaulFrields, SawyerL,RjwilmsiBot, Viper dove, Iliaskr, Benman557, DRAGON BOOSTER, Provehuman, Elium2, Florianwardell, Balph Eubank, Bimanpilot,Husseinmoien, ThDavidRuk, Kerrick Staley, Tomvanbraeckel, Nyxaus, Piotrek54321, Roney.thomas.0, EmausBot, Nikhil1234567890,Nima1024, Hrjohnson10, WikitanvirBot, Immunize, Zollerriia, Thelinuxkid, Hecta, GoingBatty, Collinrocks26, Curtis8712, Ballofstring,ZxxZxxZ, Drfrjenkins, Compsciguy1988, Huctwitha, Zaixionito, Dcirovic, Мирослав Ћика, K6ka, Bgismyfriend, Regression Tester,Icewalker~enwiki, Alisha.4m, Kkm010, ZéroBot, Cogiati, Checkingfax, Killertux666, Bollyjeff, Skiddielv1, Kennethaar, Bryce Car-mony, Krd, Iajrz, RussellGee, TheAmericanizator, Cullero, H3llBot, Babkock, Logangorence, Demonkoryu, Funkiyak, Wayne Slam,Cosman246, Alperoguz, Capricorn4049, JasePow1968, Blackwidowhex, L Kensington, Lxr1234, Palosirkka, Wikiloop, HenriqueRocha,Operation Ubuntu, RedRabbit, Mescaicedo, Wei2912, ChuispastonBot, Lioncash, Kenny Strawn, Creopterouis, JustinC474, Oshidash,Mjbmrbot, Georgy90, Ultrabud, Petrb, Jwaked, Mnicolosi, Kenny4427, ClueBot NG, Pantergraph, Maclinwright, Iamiyouareyou, LogX,This lousy T-shirt, Wikinium, Satellizer, Lostick, Strcat, Yourmomblah, Baseball Watcher, Mjt365, RocketLauncher2, Frietjes, Delusion23,Rahulghose, MrMinarion, C. Jeremy Wong, O.Koslowski, ScottSteiner, I epic win fail, Josemonmaliakal, Blakedog, Linuxpl0x, Xeno-phonix, Jebethe, Alaukikyo, TurnspitDawg, Sanketg86, Gavin.perch, Kracethekingmaker, Anupmehra, Prejeeshp, Crazymonkey1123,Mtking, Mimarsapple, Gavinstubbs09, Helpful Pixie Bot, Squidwardrocs, BubbaTLC, Kezar12356, GRANYEBOY, ProtoFire, Ndavi-dow, Exeva, Ahme t 151, Karabulutis252, Bozkurte, BG19bot, Island Monkey, Linuxsux, Rijinatwiki, Puramyun31, Franciso Linux,XXAutisticJeezusXx, Thand3, AlphaSly, Kendall-K1, StuGeiger, Byu68, Vikingwarrior5678, Acpipower5678, Kavins92, Fallacy of theMasses, Trevayne08, ASCIIn2Bme, Applelinux, RadicalRedRaccoon, Medende, Jayadevp13, Ioanthecomputerguy, Svnpenn, Lux2545,Isokiho, Merritttttt, Isacdaavid, Rubinkumar, Carliitaeliza, MeanMotherJr, Tkbx, Abhilash Mhaisne, HueSatLum, Zhaofeng Li, Inops,Cyberbot II, Angela MacLean, Timothy Gu, EuroCarGT, Tow, Dexbot, Rezonansowy, Spameliminator, MirandaStreeter, Mogism, TwoT-woHello, Jc86035, Calinou1, Rotlink, Palmbeachguy, RicardAnufriev, Aweasd, Hnfiurgds, Ruby Murray, I am One of Many, The EditorialVoice, Theemathas, Jakec, EvergreenFir, Fsandlinux, Jacob.halsey1, Myconix, Flat Out, ElHef, DavidLeighEllis, Comp.arch, Jop2~enwiki,Haminoon, Huihermit, Ant.ton.t, Kharkiv07, Buffbills7701, NorthBySouthBaranof, The Herald, OliverBel, PrivateMasterHD, My nameis not dave, Williamt5120, FDMS4, MattyWinder, Quenhitran, Paulo Jorge Tomé, Saniya2090, Jackmcbarn, Tronedit, DatEditorPen-guin, AddWittyNameHere, WallnutKraken, ScotXW, Sashaursic98, Lucky7-phool, DwellingDreamr, Tetriminos, Ariel Lindo, Sofia Luci-fairy, CarnivorousBunny, Lagoset, Monkbot, Sudsbuds, Stefenev, Helworld, Filedelinkerbot, Vieque, Jarrod lawrence69, Patelaarti2393,Ketansingh123, BethNaught, Mit Romney, OMPIRE, Aste9974, Hitechcomputergeek, Peter238, Amortias, DWIZKID10, Maulik1512,Blablabli~enwiki, Mario Castelán Castro, Fleivium, Iamahashtag, ChamithN, DarrenRainey, MuhammadSohail03, Kazoza404, Khoi D.Dinh, JAYAVAISHU, Knowledgebattle, Jeremy.rican, Orduin, Kethrus, Hchaudh3, Linuxtinkerer, SupertemplarDX, RagsGamingGamer,Pikachu9501, Godsy, Davidnotcoulthard, Sizeofint, Zoomoow, Kb333, Amit Bongir, Robinjons1515, Notarock, Uareafag, Dheer chu-dasama, Arandombunnyrabbit, Recharged, Ashmita Bichoury, Thediamondgames, KasparBot, Leowonderful, Meepermeepster, Cmat-teri, Aznashwan, Qp0qp0qp0, Grammarindian, Firejuggler86, Alex98, Edwinbubble, Fire2222, Popstheannoying, SpiffyAnarchist, Pan-cake2345 and Anonymous: 2640

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22 12 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

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