Linux

Linux This article is about the operating system. For the Distributions oriented toward desktop use typically inkernel, see Linux kernel. For other uses, see Linux clude X11, a Wayland implementation or Mir as the (disambiguation). windowing system, and an accompanying desktop environment such as GNOME or the KDE Software Compilation; some distributions may also include a less resourcei [4][5] Linux (pronounced /ˈlɪnəks/ LIN-əks or, less [5][6] frequently, /ˈlaɪnəks/ LYN-əks ) is a Unix-like and intensive desktop such as LXDE or Xfce. Distributions [7] mostly POSIX-compliant computer operating system intended to run on servers may omit all graphical environ(OS) assembled under the model of free and open-source ments from the standard install, and instead include other software development and distribution. The defining software to set up and operate a solution stack such as component of Linux is the Linux kernel,[8] an operating LAMP. Because Linux is freely redistributable, anyone system kernel first released on 5 October 1991 by Linus may create a distribution for any intended use. Torvalds.[9][10] The Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy.[11][12]

1 History

Linux was originally developed as a free operating system for personal computers based on the Intel x86 ar- Main article: History of Linux chitecture, but has since been ported to more computer hardware platforms than any other operating system.[13] Thanks to its dominance on smartphones, Android, which is built on top of the Linux kernel, has the largest installed 1.1 Antecedents base of all general-purpose operating systems.[14] Linux, in its original form, is also the leading operating system on servers and other big iron systems such as mainframe computers and supercomputers,[15][16] but is used on only around 1.5% of desktop computers[17] with Linux-based Chrome OS taking about 5% of the overall and nearly 20% of the sub-$300 notebook sales.[18] Linux also runs on embedded systems, which are devices whose operating system is typically built into the firmware and is highly tailored to the system; this includes smartphones and tablet computers running Android and other Linux derivatives,[19] TiVo and similar DVR devices, network routers, facility automation controls, televisions,[20][21] video game consoles, and smartwatches.[22] The development of Linux is one of the most prominent examples of free and open-source software collaboration. The underlying source code may be used, modified and distributed—commercially or non-commercially— by anyone under the terms of its respective licenses, such as the GNU General Public License. Typically, Linux is packaged in a form known as a Linux distribution, for both desktop and server use. Some of the popular mainstream Linux distributions are Debian, Ubuntu, Linux Mint, Fedora, openSUSE, Arch Linux and Gentoo, together with commercial Red Hat Enterprise Linux and SUSE Linux Enterprise Server distributions. Linux distributions include the Linux kernel, supporting utilities and libraries, and usually a large amount of application software to fulfill the distribution’s intended use.

Linus Torvalds, principal author of the Linux kernel

The Unix operating system was conceived and implemented in 1969 at AT&T's Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, 1

2

1 HISTORY

Douglas McIlroy, and Joe Ossanna.[23] First released in 1971, Unix was written entirely in assembly language as it was common practice at the time. Later, in a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie (with exceptions to the kernel and I/O). The availability of a high-level language implementation of Unix made its porting to different computer platforms easier.

kernel development took place on Linux systems.[31] GNU applications also replaced all MINIX components, because it was advantageous to use the freely available code from the GNU Project with the fledgling operating system; code licensed under the GNU GPL can be reused in other projects as long as they also are released under the same or a compatible license. Torvalds initiated a switch from his original license, which prohibited commercial redistribution, to the GNU GPL.[32] Developers worked to integrate GNU components with the Linux kernel, making a fully functional and free operating system.[26]

Due to an earlier antitrust case forbidding it from entering the computer business, AT&T was required to license the operating system’s source code to anyone who asked.[24] As a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs; freed of the legal obligation requiring free licensing, Bell Labs began 1.3 selling Unix as a proprietary product.

Naming

The GNU Project, started in 1983 by Richard Stallman, had the goal of creating a “complete Unix-compatible software system” composed entirely of free software. Work began in 1984.[25] Later, in 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete.[26] Linus Torvalds has said that if the GNU kernel had been available at the time (1991), he would not have decided to write his own.[27] Although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Torvalds has said that if 386BSD had been available at the time, he probably would not have created 5.25-inch floppy discs holding a very early version of Linux Linux.[28] MINIX was created by a computer science professor Linus Torvalds had wanted to call his invention Freax, a Andrew S. Tanenbaum and released in 1987 as a minimal portmanteau of “free”, “freak”, and “x” (as an allusion Unix-like operating system targeted at students and oth- to Unix). During the start of his work on the system, he ers who wanted to learn the operating system principles. stored the files under the name “Freax” for about half of a name “Linux,” Although the complete source code of MINIX was freely year. Torvalds had already considered the [33] but initially dismissed it as too egotistical. available, the licensing terms prevented it from being free software until the licensing changed in April 2000.[29]

1.2

Creation

In order to facilitate development, the files were uploaded to the FTP server (ftp.funet.fi) of FUNET in September 1991. Ari Lemmke, Torvald’s coworker at the Helsinki University of Technology (HUT) who was one of the volunteer administrators for the FTP server at the time, did not think that “Freax” was a good name. So, he named the project “Linux” on the server without consulting Torvalds.[33] Later, however, Torvalds consented to “Linux”.

In 1991, while attending the University of Helsinki, Torvalds became curious about operating systems[30] and frustrated by the licensing of MINIX, which at the time limited it to educational use only.[29] He began to work on his own operating system kernel, which eventually be- To demonstrate how the word “Linux” should be procame the Linux kernel. nounced ( i /ˈlɪnəks/ LIN-əks[4][5] ), Torvalds included an Torvalds began the development of the Linux kernel on audio guide ( listen ) with the kernel source code.[34] MINIX and applications written for MINIX were also Another variant of pronunciation is /ˈlaɪnəks/ LYNused on Linux. Later, Linux matured and further Linux əks.[5][6]

1.5

1.4

Current development

Commercial and popular uptake

3 wearables. Linux gaming is also on the rise with Valve showing its support for Linux and rolling out its own gaming oriented Linux distribution. Linux distributions have also gained popularity with various local and national governments, such as the federal government of Brazil.[45]

1.5 Current development Torvalds continues to direct the development of the kernel.[46] Stallman heads the Free Software Foundation,[47] which in turn supports the GNU components.[48] Finally, individuals and corporations develop third-party non-GNU components. These thirdUbuntu, a popular Linux distribution party components comprise a vast body of work and may include both kernel modules and user applications and Main article: Linux adoption Adoption of Linux in production environments, rather libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.

2 Design

Nexus 5 running Android

A Linux-based system is a modular Unix-like operating system, deriving much of its basic design from principles established in Unix during the 1970s and 1980s. Such a system uses a monolithic kernel, the Linux kernel, which handles process control, networking, access to the peripherals, and file systems. Device drivers are either integrated directly with the kernel, or added as modules that are loaded while the system is running.[49]

Separate projects that interface with the kernel provide much of the system’s higher-level functionality. The GNU userland is an important part of most Linux-based systems, providing the most common implementation of the C library, a popular CLI shell, and many of the common Unix tools which carry out many basic operating system tasks. The graphical user interface (or GUI) used by most Linux systems is built on top of an implementation of the X Window System.[50] More recently, the Linux community seeks to advance to Wayland as the new disToday, Linux systems are used in every domain, from play server protocol in place of X11; Ubuntu, however, embedded systems to supercomputers,[16][36] and have develops Mir instead of Wayland.[51] secured a place in server installations often using the Installed components of a Linux system include the popular LAMP application stack.[37] Use of Linux disfollowing:[50][52] tributions in home and enterprise desktops has been growing.[38][39][40][41][42][43][44] Linux distributions have • A bootloader, for example GNU GRUB, LILO, also become popular in the netbook market, with many SYSLINUX, Coreboot or Gummiboot. This is a devices shipping with customized Linux distributions inprogram that loads the Linux kernel into the comstalled, and Google releasing their own Google Chrome puter’s main memory, by being executed by the OS designed for netbooks. computer when it is turned on and after the firmware Linux’s greatest success in the consumer market is perinitialization is performed. haps the mobile device market, with Android being one • An init program, such as the traditional sysvinit and of the most dominant operating systems on smartphones and very popular on tablets and, more recently, on the newer systemd, OpenRC and Upstart. This is the than being used only by hobbyists, started to take off first in the mid-1990s in the supercomputing community, where organizations such as NASA started to replace their increasingly expensive machines with clusters of inexpensive commodity computers running Linux. Commercial use followed when Dell and IBM, followed by Hewlett-Packard, started offering Linux support to escape Microsoft's monopoly in the desktop operating system market.[35]

4

2

DESIGN

first process launched by the Linux kernel, and is at the root of the process tree: in other terms, all processes are launched through init. It starts processes such as system services and login prompts (whether graphical or in terminal mode). • Software libraries, which contain code that can be used by running processes. On Linux systems using ELF-format executable files, the dynamic linker that manages use of dynamic libraries is known as ld-linux.so. If the system is set up for the user to compile software themselves, header files will also be included to describe the interface of installed libraries. Beside the most commonly used software library on Linux systems, the GNU C Library (glibc), there are numerous other libraries. • C standard library is the library needed to run standard C programs on a computer system, with the GNU C Library being the most commonly used. Several alternatives are available, Bash, a shell developed by GNU[53] and widely used in Linux such as the EGLIBC (which was used by Debian for some time) and uClibc (which was designed for uClinux). desktop environments, such as the K Desktop Envi• Widget toolkits are the libraries used to build ronment (KDE), GNOME, Cinnamon, Unity, LXDE, graphical user interfaces (GUIs) for software Pantheon and Xfce, though a variety of additional user inapplications. Numerous widget toolkits are terfaces exist. Most popular user interfaces are based on available, including GTK+ and Clutter (soft- the X Window System, often simply called “X”. It proware) developed by the GNOME project, vides network transparency and permits a graphical appliQt developed by the Qt Project and led cation running on one system to be displayed on another by Digia, and Enlightenment Foundation Li- where a user may interact with the application; however, braries (EFL) developed primarily by the certain extensions of the X Window System are not capable of working over the network.[54] Several popular X Enlightenment team. display servers exist, with the reference implementation, • User interface programs such as command shells or X.Org Server, being the most popular. windowing environments. Several types of window managers exist for X11, includ-

2.1

User interface

The user interface, also known as the shell, is either a command-line interface (CLI), a graphical user interface (GUI), or through controls attached to the associated hardware, which is common for embedded systems. For desktop systems, the default mode is usually a graphical user interface, although the CLI is available through terminal emulator windows or on a separate virtual console. CLI shells are the text-based user interfaces, which use text for both input and output. The dominant shell used in Linux is the GNU Bourne-Again Shell (bash), originally developed for the GNU project. Most low-level Linux components, including various parts of the userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication.

ing tiling, dynamic, stacking and compositing. Window managers provide means to control the placement and appearance of individual application windows, and interact with the X Window System. Simpler X window managers such as dwm or ratpoison provide a minimalist functionality, while more elaborate window managers such as FVWM, Enlightenment or Window Maker provide more features such as a built-in taskbar and themes, but are still lightweight when compared to desktop environments. Desktop environments include window managers as part of their standard installations, such as Mutter (GNOME), KWin (KDE) or Xfwm (xfce), although users may choose to use a different window manager if preferred.

Wayland is a display server protocol intended as a replacement for the X11 protocol; as of 2014, Wayland has not received wider adoption. Unlike X11, Wayland does not need an external window manager and compositing manager. Therefore, a Wayland compositor takes the role of the display server, window manager and compositing manager. Weston is the reference implementation of On desktop systems, the most popular user interfaces Wayland, while GNOME’s Mutter and KDE’s KWin are are the GUI shells, packaged together with extensive being ported to Wayland as standalone display servers.

3.1

Community

5

Enlightenment has already been successfully ported to Linux based distributions are intended by developers Wayland since version 19. for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX,[59] SUS,[60] LSB, ISO, and ANSI standards where possible, although to date only one Linux distribu2.2 Video input infrastructure tion has been POSIX.1 certified, Linux-FT.[61][62] Main article: Video4Linux

Free software projects, although developed through collaboration, are often produced independently of each Linux currently has two modern kernel-userspace APIs other. The fact that the software licenses explicitly permit for handing video input devices: V4L2 API for video redistribution, however, provides a basis for larger scale streams and radio, and DVB API for digital TV projects that collect the software produced by stand-alone projects and make it available all at once in the form of a reception.[55] Linux distribution. Due to the complexity and diversity of different devices, and due to the large amount of formats and standards han- Many Linux distributions, or “distros”, manage a remote dled by those APIs, this infrastructure needs to evolve to collection of system software and application software better fit other devices. Also, a good userspace device packages available for download and installation through library is the key of the success for having userspace ap- a network connection. This allows users to adapt the opplications to be able to work with all formats supported erating system to their specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer by those devices.[56][57] organizations, and commercial entities. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more gener3 Development ally integration of the different software packages into a coherent whole. Distributions typically use a package manager such as apt, yum, zypper, pacman or portage to install, remove and update all of a system’s software from one central location. 1970

1980

1990

2000

9.1

NetBSD

BSD family

6.0.1

OpenBSD BSD (Berkeley Software Distribution) Bill Joy

SunOS

Time

2010

FreeBSD

5.3

4.4

4.1.4 Darwin NextStep 3.3

Mac OS X

Xenix OS

10.8.4

Apple

Microsoft/SCO

3.1 Community

GNU/Hurd K16

GNU Richard Stallman Minix

GNU/Linux

3.10.9

Linus Torvalds

3.2.1

Andrew S. Tanenbaum Research UNIX Bell Labs: Ken Thompson, Dennis Ritchie, et al.

10.5 Commercial UNIX

See also: Free software community and Linux User Group

UnixWare Univel/SCO

AT&T

Solaris Sun Microsystems

11 11/11

A distribution is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis, Debian being a wellknown example. Others maintain a community version Simplified history of Unix-like operating systems. Linux shares of their commercial distributions, as Red Hat does with similar architecture and concepts (as part of the POSIX standard) Fedora and SUSE does with openSUSE. System III & V family

11i v3

HP-UX

7.1 TL1

AIX IBM

IRIX

6.5.30

SGI

but does not share non-free source code with the original Unix or MINIX.

Main articles: Linux distribution and Free software

In many cities and regions, local associations known as Linux User Groups (LUGs) seek to promote their preferred distribution and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. Many Internet communities also provide support to Linux users and developers. Most distributions and free software / open-source projects have IRC chatrooms or newsgroups. Online forums are another means for support, with notable examples being LinuxQuestions.org and the various distribution specific support and community forums, such as ones for Ubuntu, Fedora, and Gentoo. Linux distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list.

The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open-source software. Linux is not the only such operating system, although it is by far the most widely used.[58] Some free and open-source software licenses are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU General Public License (GPL), is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU Project. There are several technology websites with a Linux

6

4

HARDWARE SUPPORT

focus. Print magazines on Linux often include in terms of terminal programming or QuickBASIC or cover disks including software or even complete Linux Turbo BASIC programming in the form of QB64. distributions.[63][64] A common feature of Unix-like systems, Linux includes Although Linux distributions are generally available with- traditional specific-purpose programming languages tarout charge, several large corporations sell, support, and geted at scripting, text processing and system configuracontribute to the development of the components of the tion and management in general. Linux distributions supsystem and of free software. An analysis of the Linux ker- port shell scripts, awk, sed and make. Many programs nel showed 75 percent of the code from December 2008 also have an embedded programming language to support to January 2010 was developed by programmers working configuring or programming themselves. For example, for corporations, leaving about 18 percent to volunteers regular expressions are supported in programs like grep, and 7% unclassified.[65] Major corporations that provide or locate, while advanced text editors, like GNU Emacs, contributions include Dell, IBM, HP, Oracle, Sun Mi- have a complete Lisp interpreter built-in. crosystems (now part of Oracle), SUSE, and Nokia. A Most distributions also include support for PHP, Perl, number of corporations, notably Red Hat, Canonical, and Ruby, Python and other dynamic languages. While not as SUSE, have built a significant business around Linux dis- common, Linux also supports C# (via Mono), Vala, and tributions. Scheme. A number of Java Virtual Machines and develThe free software licenses, on which the various software packages of a distribution built on the Linux kernel are based, explicitly accommodate and encourage commercialization; the relationship between a Linux distribution as a whole and individual vendors may be seen as symbiotic. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks.

opment kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM’s J2SE RE, as well as many open-source projects like Kaffe and JikesRVM.

GNOME and KDE are popular desktop environments and provide a framework for developing applications. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated development environments available including Anjuta, Code::Blocks, CodeLite, Eclipse, Geany, ActiveState Komodo, KDevelop, Lazarus, MonoDevelop, NetBeans, Another business model is to give away the software in and Qt Creator, while the long-established editors Vim, order to sell hardware. This used to be the norm in the nano and Emacs remain popular.[66] computer industry, with operating systems such as CP/M, Apple DOS and versions of Mac OS prior to 7.6 freely copyable (but not modifiable). As computer hardware 4 Hardware support standardized throughout the 1980s, it became more difficult for hardware manufacturers to profit from this tactic, Hardware as the OS would run on any manufacturer’s computer that Linux kernel shared the same architecture. Human-MachineInterface

Distributed Computing

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

3.2

Programming on Linux

Linux distributions support dozens of programming languages. The original development tools used for building both Linux applications and operating system programs are found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for Ada, C, C++, Go and Fortran. Many programming languages have a cross-platform reference implementation that supports Linux, for example PHP, Perl, Ruby, Python, Java, Go, Rust and Haskell. First released in 2003, the LLVM project provides an alternative cross-platform open-source compiler for many languages. Proprietary compilers for Linux include the Intel C++ Compiler, Sun Studio, and IBM XL C/C++ Compiler. BASIC in the form of Visual Basic is supported in such forms as Gambas, FreeBASIC, and XBasic, and

Touch-Display Attitude sensor, Motion sensor, Speech recognition

Speech recognition Attitude sensor Motion sensor

Display, Sound Vibration

Desktop Computer Workstation Home Computer Desktop replacement laptop Thin client

Mobile computer Note-/ Net-/ Smartbook Tablet Smartphone PDA / Handheld game console

Wearable Computer Wristwatch Virtual Retina Display Head-mounted display

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

Real-time computing (RTC)

Customer-premises equipment Measurement Equipment Laboratory Equipment Layer3-Switches other embedded systems

Linux Process Scheduler Linux Security Modules Linux Network scheduler Network stack Netfilter Linux device drivers Linux file system drivers

Routing daemons

Software Development Package management systems

CAD, CAM & CAE Software Office Image Processing Desktop Publishing (DTP)

Windowing Systems

Distributed computing

High-performance computing (HPC)

Graphical User Interfaces (Shells)

(SSH, HTTP, ...)

Pool of free and open-source and proprietary software

remote

Web server solution stacks (LAMP)

Supercomputer Computer Cluster Mainframe computer

Desktop UI Touch UI

Wearable UI

Video processing software 3D computer graphics Computer animation Motion graphics

Digital Audio Workstation DJ Mixing Software Video games Home cinema solutions

Debian software archives: 37,000 software packages

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 architectures, including the hand-held ARM-based iPAQ and the IBM mainframes System z9 or System z10 – covering devices ranging from mobile phones to supercomputers.[67] Specialized distributions and kernel forks exist for less mainstream architectures; for example, the ELKS ker-

5.1

Desktop

7

nel fork can run on Intel 8086 or Intel 80286 16-bit microprocessors, while the µClinux kernel fork may run on systems without a memory management unit. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as Macintosh computers (with both PowerPC and Intel processors), PDAs, video game consoles, portable music players, and mobile phones.

default GNOME Shell and Ubuntu Unity), and the KDE Plasma Desktop. No single official Linux desktop exists: rather desktop environments and Linux distributions select components from a pool of free and open-source software with which they construct a GUI implementing some more or less strict design guide. GNOME, for example, has its human interface guidelines as a design guide, which gives the human–machine interface an important role, not just when doing the graphical design, but also when considering people with disabilities, and even when focusing on security.[71]

There are several industry associations and hardware conferences devoted to maintaining and improving support for diverse hardware under Linux, such as FreedomHEC. Over time, support for different hardware has improved in Linux, resulting in any off-the-shelf pur- The collaborative nature of free software development alchase having a “good chance” of being compatible.[68] lows distributed teams to perform language localization of some Linux distributions for use in locales where localizing proprietary systems would not be cost-effective. For 5 Uses example, the Sinhalese language version of the Knoppix distribution became available significantly before Microsoft translated Windows XP into Sinhalese. In this See also: Linux range of use case the Lanka Linux User Group played a major part in developing the localized system by combining the knowlBeside the Linux distributions designed for generaledge of university professors, linguists, and local develpurpose use on desktops and servers, distributions may opers. be specialized for different purposes including: computer architecture support, embedded systems, stability, security, localization to a specific region or language, target- 5.1.1 Performance and applications ing of specific user groups, support for real-time applications, or commitment to a given desktop environment. The performance of Linux on the desktop has been a Furthermore, some distributions deliberately include only controversial topic; for example in 2007 Con Kolivas acfree software. As of 2015, over four hundred Linux dis- cused the Linux community of favoring performance on tributions are actively developed, with about a dozen dis- servers. He quit Linux kernel development out of frustributions being most popular for general-purpose use.[69] tration with this lack of focus on the desktop, and then

Desktop

Desktop widgets

Plasma 2

Enlight. DR19

Cinnamon

2D Application

Media Application

3D Application

possibly adaptations to Wayland/Mir

possibly adaptations to Wayland/Mir

possibly adaptations to Wayland/Mir

User Interface Toolkits (in the form of libraries):

Cairo-Dock

GNOME Shell

Desktop Shells:

GTK+ Pango ATK Clutter Cairo (Xr)

Widgets for Unity and Plasma Ubuntu

Qt

EFL

SDL

libwayland-client

libwayland-client

libwayland-client

GNUstep wxWidgets FLTK ...

Android

Unity

5.1

libwayland-client libX/libXCB

libwayland / COGL

gave a “tell all” interview on the topic.[72] Since then a significant amount of development has focused on improving the desktop experience. Projects such as Upstart and systemd aim for a faster boot time; the Wayland and Mir projects aim at replacing X11 while enhancing desktop performance, security and appearance.[73]

Many popular applications are available for a wide variety of operating systems. For example, Mozilla Firefox, OpenOffice.org/LibreOffice and Blender have downloadLinux kernel, able versions for all major operating systems. FurtherLinux kernel more, some applications initially developed for Linux, CPU & GPU Hardware such as Pidgin, and GIMP, were ported to other operating systems (including Windows and Mac OS X) due to their Visible software components of the Linux desktop stack include the display server, widget engines, and some of the more popularity. In addition, a growing number of proprietary [74] such widespread widget toolkits. There are also components not di- desktop applications are also supported on Linux, as Autodesk Maya, Softimage XSI and Apple Shake in rectly visible to end users, including D-Bus and PulseAudio. the high-end field of animation and visual effects; see the See also: Desktop environment and Linux adoption: List of proprietary software for Linux for more details. Measuring desktop adoption There are also several companies that have ported their own or other companies’ games to Linux, with Linux also The popularity of Linux on standard desktop computers being a supported platform on both the[75]popular Steam and laptops has been increasing over the years.[70] Cur- and Desura digital-distribution services. rently most distributions include a graphical user envi- Many other types of applications available for Microsoft ronment, with the two most popular environments being Windows and Mac OS X also run on Linux. Commonly, GNOME (which can utilize additional shells such as the either a free software application will exist which does the kms (Kernel Mode Setting) drm (Direct Rendering Manager)

? kdbus ?

unetwork

NetworkManager

packagekitd

GLib

GObject Glib GModule GThread GIO

Alternative display servers:

PulseAudio-d

libinput

evdev

glibc µClibc

systemd

libwayland-server

Wayland Compositor

(contains udev)

weston, clayton, mutter, KWin

udisks

System daemons:

avahi-daemon

System libraries:

D-Bus-Daemon

Display server:

kmod-fs-ext4

libxserver

X-Server

window manager

X.Org Xfree86 X-Win32 X11.app

metacity mutter KWin Compiz

netfilter

device drivers & other modules

radeon nouveau lima etna_viv freedreno tegra-re

Keyboard & Mouse Touch-Screen BrailleDisplay

cache coherent L2-Caches main memory

ALSA: emu20k1, ctxfi, hda... kmod-ltq-atm-vr9

ath9k

UMTS/CDMA/LTE GPS-receiver G-sensor

libmir-serv

mir mir

SF

window manager

SurfaceFlinger

Compiz

SELinux TOMOYO Smack AppArmor

Ethernet 802.11-(abc) Bluetooth

libhybris

window manager AWM

libbionic

binder ashmem pmem wakelocks logger ...

(Android-forked)

8

5

USES

functions of an application found on another operating • KDE Plasma (KDE 4) system, or that application will have a version that works • LXDE on Linux, such as with Skype and some video games like Dota 2 and Team Fortress 2. Furthermore, the Wine • MATE (GNOME 2) project provides a Windows compatibility layer to run unmodified Windows applications on Linux. It is spon• Pantheon sored by commercial interests including CodeWeavers, • Sugar which produces a commercial version of the software. Since 2009, Google has also provided funding to the • Trinity (KDE 3) Wine project.[76][77] CrossOver, a proprietary solution based on the open-source Wine project, supports run• Unity ning Windows versions of Microsoft Office, Intuit appli• Xfce cations such as Quicken and QuickBooks, Adobe Photoshop versions through CS2, and many popular games such as World of Warcraft. In other cases, where there is no 5.2 Netbooks Linux port of some software in areas such as desktop pub[78] [79][80][81] lishing and professional audio, there is equivLinux distributions have also become popular in the alent software available on Linux. netbook market, with many devices such as the ASUS Eee PC and Acer Aspire One shipping with customized Linux distributions installed.[82] 5.1.2 Components and installation Besides externally visible components, such as X window managers, a non-obvious but quite central role is played by the programs hosted by freedesktop.org, such as DBus or PulseAudio; both major desktop environments (GNOME and KDE) include them, each offering graphical front-ends written using the corresponding toolkit (GTK+ or Qt). A display server is another component, which for the longest time has been communicating in the X11 display server protocol with its clients; prominent software talking X11 includes the X.Org Server and Xlib. Frustration over the cumbersome X11 core protocol, and especially over its numerous extensions, has led to the creation of a new display server protocol, Wayland. Installing, updating and removing software in Linux is typically done through the use of package managers such as the Synaptic Package Manager, PackageKit, and Yum Extender. While most major Linux distributions have extensive repositories, often containing tens of thousands of packages, not all the software that can run on Linux is available from the official repositories. Alternatively, users can install packages from unofficial repositories, download pre-compiled packages directly from websites, or compile the source code by themselves. All these methods come with different degrees of difficulty; compiling the source code is in general considered a challenging process for new Linux users, but it is hardly needed in modern distributions and is not a method specific to Linux. • Samples of graphical desktop environments • Cinnamon • Common Desktop Environment (CDE) • Enlightenment • GNOME Shell (GNOME 3)

In 2009, Google announced its Google Chrome OS, a minimal Linux based operating system which application consists only of the Google Chrome browser, a file manager and a media player.[83] The netbooks that shipped with the operating system, termed Chromebooks, started appearing in the market in June 2011.[84]

5.3 Servers, mainframes and supercomputers Web cache

Linux kernel

Squid Polipo Traffic server

AppArmor SELinux Smack TOMOYO

Process Scheduler

Web server Apache Cherokee Lighttpd Nginx

CGI scripting Perl PHP Python

Database MariaDB MySQL Drizzle

Netfilter

Environment: CCC

Hardware CPU & RAM

Crackers Botnets for DDoS-attacks cracking attempts ...

Attacks stave off

Network scheduler NIC device driver kmod-fs-ext4 kmod-fs-btrfs Lustre ...

Competitors

& Requests

Linux network stack

compete for customers

serve

Networking hardware

Internet Responses

Customers

low latency

Storage SATA SAS RAID iSCSI NAS

want attendance

Botnets DDoS-Attacks

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

Linux distributions have long been used as server operating systems, and have risen to prominence in that area; Netcraft reported in September 2006, that eight of the ten most reliable internet hosting companies ran Linux distributions on their web servers.[85] Since June 2008, Linux distributions represented five of the top ten, FreeBSD three of ten, and Microsoft two of ten;[86] since February 2010, Linux distributions represented six of the top ten, FreeBSD two of ten, and Microsoft one of ten.[87] Linux distributions are the cornerstone of the LAMP server-software combination (Linux, Apache,

5.5

Embedded devices

9

MariaDB/MySQL, Perl/PHP/Python) which has vor of Tizen, an operating system targeted at mobile deachieved popularity among developers, and which is one vices as well as in-vehicle infotainment (IVI). Tizen is a of the more common platforms for website hosting.[88] project within The Linux Foundation. Several Samsung Samsung Gear 2 beLinux distributions have become increasingly popular on products are already running Tizen, [95] ing the most significant example. Samsung Z smartmainframes in the last decade partly due to pricing and [96] phones will use Tizen instead of Android. [16] the open-source model. In December 2009, computer giant IBM reported that it would predominantly market As a result of MeeGo’s termination, the Mer project and sell mainframe-based Enterprise Linux Server.[89] forked the MeeGo codebase to create a basis for mobile[97] In July 2012, Jolla anLinux distributions are also commonly used as operating oriented operating systems. nounced Sailfish OS, their own mobile operating system systems for supercomputers; in the decade since Earth built upon Mer technology. Simulator supercomputer, all the fastest supercomputers have used Linux. As of November 2014, 97% of the Mozilla’s Firefox OS consists of the Linux kernel, a world’s 500 fastest supercomputers run some variant of hardware abstraction layer, a web standards based runLinux,[90] including the top 80.[91] time environment and user interface, and an integrated web browser.[98]

5.4

Smart devices

Canonical has released Ubuntu Touch, its own mobile operating system that aims to bring convergence to the user experience on the operating system and its desktop counterpart, Ubuntu. The operating system also provides a full Ubuntu desktop when connected to an external monitor.[99]

5.5 Embedded devices See also: Embedded Linux and Linux devices Due to its low cost and ease of customization, Linux

Android smartphones

Several operating systems for smart devices, such as smartphones, tablet computers, smart TVs, and in-vehicle infotainment (IVI) systems, are based on Linux. Major platforms for such systems include Android, Firefox OS, Mer and Tizen. Android has become the dominant mobile operating system 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, and Android smart TVs and in-vehicle infotainment systems have also appeared in the market.

The Jolla Phone has the Linux-based Sailfish OS

is often used in embedded systems. In the nonmobile telecommunications equipment sector, the majority of customer-premises equipment (CPE) hardware Cell phones and PDAs running Linux on open-source runs some Linux-based operating system. OpenWrt is platforms became more common from 2007; examples a community driven example upon which many of the include the Nokia N810, Openmoko's Neo1973, and the OEM firmwares are based. Motorola ROKR E8. Continuing the trend, Palm (later For example, the popular TiVo digital video recorder acquired by HP) produced a new Linux-derived operat- also uses a customized Linux,[101] as do several network ing system, webOS, which is built into its line of Palm firewalls and routers from such makers as Cisco/Linksys. Pre smartphones. The Korg OASYS, the Korg KRONOS, the Yamaha Nokia's Maemo, one of the earliest mobile operating systems, was based on Debian.[93] It was later merged with Intel's Moblin, another Linux-based operating system, to form MeeGo.[94] The project was later terminated in fa-

Motif XS/Motif XF music workstations,[102] Yamaha S90XS/S70XS, Yamaha MOX6/MOX8 synthesizers, Yamaha Motif-Rack XS tone generator module, and Roland RD-700GX digital piano also run Linux. Linux

10

5

USES

5.6 Gaming Main article: Linux gaming There had been several games that run on traditional desktop Linux, and many of which originally written for desktop OS. However, due to most game developers not paying attention to such a small market as desktop Linux, only a few prominent games have been available for desktop Linux. On the other hand, as a popular mobile platform, Android has gained much developer interest and there are many games available for Android. In-car entertainment system of the Tesla Model S is based on Ubuntu[100]

On 14 February 2013, Valve released a Linux version of Steam, a popular game distribution platform on PC.[104] Many Steam games were ported to Linux.[105] On 13 December 2013, Valve released SteamOS, a gaming oriented OS based on Debian, for beta testing, and has plans to ship Steam Machines as a gaming and entertainment platform.[106] Valve has also developed VOGL, an OpenGL debugger intended to aid video game development,[107] as well as porting its Source game engine to desktop Linux.[108] As a result of Valve’s effort, several prominent games such as DotA 2, Team Fortress 2, Portal, Portal 2 and Left 4 Dead 2 are now natively available on desktop Linux. On 31 July 2013, Nvidia released Shield as an attempt to use Android as a specialized gaming platform.[109]

5.7 Specialized uses Due to the flexibility, customizability and free and opensource nature of Linux, it becomes possible to highly tune Linux for a specific purpose. There are two main methods for creating a specialized Linux distribution: building from scratch or from a general-purpose distribution as a base. The distributions often used for this purpose include Debian, Fedora, Ubuntu (which is itself based on Debian), Arch Linux, Gentoo, and Slackware. In contrast, Linux distributions built from scratch do not have general-purpose bases; instead, they focus on the JeOS philosophy by including only necessary components and avoiding resource overhead caused by components considered redundant in the distribution’s use cases. 5.7.1 Home theater PC

Nokia X, a smartphone that runs Linux kernel

A home theater PC (HTPC) is a PC that is mainly used as an entertainment system, especially a Home theater system. It is normally connected to a television, and often an additional audio system.

OpenELEC, a Linux distribution that incorporates the media center software Kodi, is an OS tuned specifically for an HTPC. Having been built from the ground up adis also used in stage lighting control systems, such as the hering to the JeOS principle, the OS is very lightweight WholeHogIII console.[103] and very suitable for the confined usage range of an

11 HTPC.

5.7.5 Teaching

There are also special editions of Linux distributions Linux distributions have been created to provide handsthat include the MythTV media center software, such as on experience with coding and source code to students, Mythbuntu, a special edition of Ubuntu. on devices such as the Raspberry Pi. In addition to producing a practical device, the intention is to show students “how things work under the hood”. 5.7.2 Digital security Kali Linux is a Debian-based Linux distribution designed for digital forensics and penetration testing. It comes preinstalled with several software applications for penetration testing and identifying security exploits.[110] 5.7.3

6 Market share and uptake Main article: Linux adoption See also: Usage share of operating systems

System rescue

Many quantitative studies of free/open-source software focus on topics including market share and reliability, with numerous studies specifically examining Linux.[114] The Linux market is growing rapidly, and the revenue of servers, desktops, and packaged software running Linux was expected to exceed $35.7 billion by 2008.[115] Analysts and proponents attribute the relative success of Linux to its security, reliability, low cost, and freedom • GParted Live – a Debian-based distribution devel- from vendor lock-in.[116][117] oped by the GParted project.

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

Desktops and laptops According to web server statistics, as of March 2015, the estimated market share • SystemRescueCD – a Gentoo-based distribution of Linux on desktop computers is around 1.5%. In with support for editing Windows registry. comparison, Microsoft Windows has a market share of around 91.5%, while Mac OS covers around 7%.[17] 5.7.4 In space • Parted Magic – a commercial Linux distribution.

stats that use the top SpaceX uses multiple redundant flight computers in a Web servers W3Cook publishes[118] one million Alexa domains, which as of May fault-tolerant design in the Falcon 9 rocket. Each Merlin 2015 estimate that 96.55% of web servers run engine is controlled by three voting computers, with two Linux, 1.73% run Windows, and 1.72% run physical processors per computer that constantly check [119] FreeBSD. W3Techs publishes stats that use the each other’s operation. Linux is not inherently faulttop ten million Alexa domains, which is updated evtolerant (no operating system is, as it is a function of the [120] ery month and as of May 2015 estimates that whole system including the hardware), but the flight com32.6% of web servers run Windows, with the rest [111] puter software makes it so for its purpose. For flex[121] being Linux or Unix. IDC's Q1 2007 report inibility, commercial off-the-shelf parts and system-wide dicated that Linux held 12.7% of the overall server “radiation-tolerant” design are used instead of radiation market at that time;[122] this estimate was based on hardened parts.[111] As of June 2015, SpaceX has made the number of Linux servers sold by various compa19 launches of the Falcon 9 since 2010, out of which nies, and did not include server hardware purchased 18 have successfully delivered their primary payloads separately that had Linux installed on it later. In to Earth orbit, including some support missions for the September 2008, Microsoft’s CEO Steve Ballmer International Space Station. stated that 60% of web servers ran Linux, versus In addition, Windows was used as an operating system 40% that ran Windows Server.[123] on non-mission critical systems—laptops used on board the space station, for example—but it has been replaced Mobile devices Android, which is based on the Linux with Linux; the first Linux-powered humanoid robot is kernel, has become the dominant operating system also undergoing in-flight testing.[112] for smartphones. During the second quarter of The Jet Propulsion Laboratory has used Linux for a number of years “to help with projects relating to the construction of unmanned space flight and deep space exploration"; NASA uses Linux in robotics in the Mars rover, and Ubuntu Linux to “save data from satellites”.[113]

2013, 79.3% of smartphones sold worldwide used Android.[92] Android is also a popular operating system for tablets, being responsible for more than 60% of tablet sales as of 2013.[124] According to web server statistics, as of December 2014 Android has a

12

7

COPYRIGHT, TRADEMARK, AND NAMING

market share of about 46%, with iOS holding 45%, It would also be impractical to obtain permission from all and the remaining 9% attributed to various niche the copyright holders, who number in the thousands.[143] platforms.[125] A 2001 study of Red Hat Linux 7.1 found that this distribution contained 30 million source lines of code.[144] UsFilm production For years Linux has been the plat- ing the Constructive Cost Model, the study estimated that form of choice in the film industry. The first this distribution required about eight thousand man-years major film produced on Linux servers was 1997’s of development time. According to the study, if all this Titanic.[126][127] Since then major studios includ- software had been developed by conventional proprietary ing DreamWorks Animation, Pixar, Weta Digital, means, it would have cost about $1.48 billion (2015 US and Industrial Light & Magic have migrated to dollars) to develop in the United States.[144] Most of the Linux.[128][129][130] According to the Linux Movies source code (71%) was written in the C programming Group, more than 95% of the servers and desktops language, but many other languages were used, includat large animation and visual effects companies use ing C++, Lisp, assembly language, Perl, Python, Fortran, Linux.[131] and various shell scripting languages. Slightly over half of all lines of code were licensed under the GPL. The Linux Use in government Linux distributions have also kernel itself was 2.4 million lines of code, or 8% of the [144] gained popularity with various local and national total. governments. The federal government of Brazil In a later study, the same analysis was performed is well known for its support for Linux.[132][133] for Debian version 4.0 (etch, which was released in News of the Russian military creating its own 2007).[145] This distribution contained close to 283 milLinux distribution has also surfaced, and has come lion source lines of code, and the study estimated that it to fruition as the G.H.ost Project.[134] The Indian would have required about seventy three thousand manstate of Kerala has gone to the extent of mandating years and cost US$8.16 billion (in 2015 dollars) to dethat all state high schools run Linux on their velop by conventional means. computers.[135][136] China uses Linux exclusively as the operating system for its Loongson processor family to achieve technology independence.[137] In Spain, some regions have developed their own Linux distributions, which are widely used in education and official institutions, like gnuLinEx in Extremadura and Guadalinex in Andalusia. France and Germany have also taken steps toward the adoption of Linux.[138]

7

Copyright, trademark, and naming

See also: GNU/Linux naming controversy and SCOLinux controversies Linux kernel is licensed under the GNU General Public License (GPL), version 2. The GPL requires that anyone who distributes software based on source code under this license, must make the originating source code (and any modifications) available to the recipient under the same terms.[139] Other key components of a typical Linux distribution are also mainly licensed under the GPL, but they may use other licenses; many libraries use the GNU Lesser General Public License (LGPL), a more permissive variant of the GPL, and the X.org implementation of the X Window System uses the MIT License.

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

In the United States, the name Linux is a trademark registered to Linus Torvalds.[3] Initially, nobody registered it, but on 15 August 1994, William R. Della Croce, Jr. filed for the trademark Linux, and then demanded royalties from Linux distributors. In 1996, Torvalds and some affected organizations sued him to have the trademark assigned to Torvalds, and, in 1997, the case was settled.[146] The licensing of the trademark has since been handled by the Linux Mark Institute. Torvalds has stated that he trademarked the name only to prevent someone else from using it. LMI originally charged a nominal sublicensing [147] Torvalds states that the Linux kernel will not move from fee for use of the Linux name as part of trademarks, favor of offering a free, perpetual version 2 of the GPL to version 3.[140][141] He specifically but later changed this in [148] worldwide sublicense. dislikes some provisions in the new license which prohibit the use of the software in digital rights management.[142] 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 GNU operating system, initiated in 1983 by Richard Stallman, president of the Free Software Foundation.[11][12] A minority of public figures and software projects other than Stallman and the Free Software Foundation, notably Debian (which had been sponsored by the Free Software Foundation up to 1996[149] ), also use GNU/Linux when referring to the operating system as a whole.[101][150][151] Most media and common usage, however, refers to this family of operating systems simply as Linux, as do many large Linux distributions (for example, SUSE Linux and Red Hat). As of May 2011, about 8% to 13% of a modern Linux distribution is made of GNU components (the range depending on whether GNOME is considered part of GNU), as determined by counting lines of source code making up Ubuntu’s “Natty” release; meanwhile, about 9% 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 environments • Criticism of Linux • Linux Documentation Project

• List of games released on Linux

[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 Linux Standard Base”. opengroup.org. 2003-07-29. Retrieved 2014-04-27. [8] Eckert, Jason W. (2012). Linux+ Guide to Linux Certification (Third ed.). Boston, Massachusetts: Cengage Learning. p. 33. ISBN 978-1111541538. Retrieved April 14, 2013. The shared commonality of the kernel is what defines Linux; the differing OSS applications that can interact with the common kernel are what differentiate Linux distributions. [9] Linus Benedict Torvalds (5 October 1991). “Free minix-like kernel sources for 386-AT”. Newsgroup: comp.os.minix. Retrieved September 30, 2011. [10] “What Is Linux: An Overview of the Linux Operating System”. Linux Foundation. April 3, 2009. Retrieved August 15, 2011.

[13] Barry Levine (26 August 2013). “Linux' 22th [sic] Birthday Is Commemorated - Subtly - by Creator”. Simpler Media Group, Inc. Retrieved 10 May 2015. Originally developed for Intel x86-based PCs, Torvalds’ “hobby” has now been released for more hardware platforms than any other OS in history.

• List of operating systems • Loadable kernel module • Linus Torvalds § Possible NSA approach

[14] "NetMarketShare:Mobile/Tablet Operating System Market Share”.

• Usage share of operating systems

10

[4] “Re: How to pronounce Linux?". Newsgroup: comp.os.linux. 23 April 1992. Usenet: [email protected]. Retrieved January 9, 2007.

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

• List of Linux distributions

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

Notes

[1] “Linux” trademark is owned by Linus Torvalds ministered by the Linux Mark Institute.

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

[11] “GNU/Linux FAQ”. Gnu.org. Retrieved 1 September 2013.

• Linux Foundation

9

[2] “The Linux Kernel Archives: Frequently asked questions”. kernel.org. September 2, 2014. Retrieved September 4, 2015.

[3]

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[16] Lyons, Daniel (March 15, 2005). “Linux rules supercomputers”. Forbes. Retrieved February 22, 2007. [17] “Desktop Operating System Market Share”. Netmarketshare.com. Retrieved March 15, 2015. [18] Steven J. Vaughan-Nichols. “Chromebook shipments leap by 67 percent”. ZDNet. Retrieved September 29, 2015. [19] Linux Devices (January 2010). “Trolltech rolls “complete” Linux smartphone stack”. Archived from the original on 2012-05-25. Retrieved September 29, 2009.

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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 Format 1992–2010 • A list of free Linux distributions, provided by the Free Software Foundation

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12 12.1

TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

Text and image sources, contributors, and licenses 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, David Merrill, Malcolm Farmer, Ffaker, Amillar, Youssefsan, XJaM, Arvindn, Christian List, Matusz, Phil Bordelon, Fubar Obfusco, MadSurgeon, 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, Michael Hardy, 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, Angela, 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 Stansifer, Dysprosia, Hydnjo, Jay, Enigmasoldier, Zoicon5, Hdk, DJ Clayworth, CBDunkerson, Lotas, Halmonster, Maximus Rex, Jeffrey Smith, 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, Centrx, Giftlite, Julianp, Mshonle~enwiki, DavidCary, Elf, Sj, Jtg, Axeman, Nichalp, Markvs, Massysett, Tobiah, Kenny sh, Ævar Arnfjörð Bjarmason, 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, Yardcock, Quadell, Emphazy, Antandrus, Demonslave, Onco p53, Joeblakesley, Estel~enwiki, Robert Brockway, Quarl, Melikamp, Bongbang, 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, Gscshoyru, 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. 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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, Thunderbird2, 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 Love Pi, ThomasJensenDaugaard, Boxxertrumps, Mr. Maka, Martinsanders, Mrmister001, Thejackisback, Pitilessbronze, Ham Pastrami, Jerryobject, 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, Millstream3, Macy, Hatster301, Jorgen W, Pascal Steger, Nancy, KritonK, Svick, Maelgwnbot, Aa00076765aa, Rkarlsba, Soleedges, RedBlade7, 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, ImperfectlyInformed, 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, Somekindofusername, W4otn, SF007, Valdis.vitolins, DumZiBoT, Templarion, Steveozone, Chris1834, Hogman500, XLinkBot, Blaznspadz, Fleeson,

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TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

Aaron north, Fastily, Ptfbending, Koolabsol, Xray7224, Marriottn, PseudoOne, SakJur, Estemi, Rror, Bradv, Dthomsen8, Btvideo, Leorojas82, 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, Thunderpenguin, Laskdfj456, Michael2346, Pclunixos, Debresser, LinkFA-Bot, Jasper Deng, Jake7401, Fireaxe888, Tsange, Peter Napkin Dance Party, 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, IncidentalPoint, Rjanag, Jose278, Royote, Keithbob, AdjustShift, Earizon, Flewis, Aaron dub, Mann jess, Frebel93, Skkamath, Materialscientist, Kr0n05931, The High Fin Sperm Whale, Citation bot, Carlsotr, Maxis ftw, Kellogg257~enwiki, Neurolysis, ArthurBot, Quebec99, Diddy29, The Firewall, MauritsBot, Xqbot, ChicagoDilettante, Timir2, Capricorn42, Y.P.Y, CoolingGibbon, 4twenty42o, Miracleworker5263, 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, 2ndAccount, 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, Simple Bob, 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, Footwarrior, 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 Carmony, 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, Xenophonix, Jebethe, Alaukikyo, TurnspitDawg, Sanketg86, Gavin.perch, Kracethekingmaker, Anupmehra, Prejeeshp, Crazymonkey1123, Mtking, Mimarsapple, Gavinstubbs09, Helpful Pixie Bot, Squidwardrocs, BubbaTLC, Kezar12356, GRANYEBOY, ProtoFire, Ndavidow, 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 the Masses, 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, TwoTwoHello, Jc86035, Calinou1, Rotlink, Palmbeachguy, RicardAnufriev, Aweasd, Hnfiurgds, Ruby Murray, I am One of Many, The Editorial Voice, 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 name is not dave, Williamt5120, FDMS4, MattyWinder, Quenhitran, Paulo Jorge Tomé, Saniya2090, Jackmcbarn, Tronedit, DatEditorPenguin, AddWittyNameHere, WallnutKraken, ScotXW, Sashaursic98, Lucky7-phool, DwellingDreamr, Tetriminos, Ariel Lindo, Sofia Lucifairy, 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 chudasama, Arandombunnyrabbit, Recharged, Ashmita Bichoury, Thediamondgames, KasparBot, Leowonderful, Meepermeepster, Cmatteri, Aznashwan, Qp0qp0qp0, Grammarindian, Firejuggler86, Alex98, Edwinbubble, Fire2222, Popstheannoying, SpiffyAnarchist, Pancake2345 and Anonymous: 2640

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Images

• File:Bash_demo.png Source: https://upload.wikimedia.org/wikipedia/commons/8/84/Bash_demo.png License: GPL Contributors: Own work Original artist: Chealer • File:Commons-logo.svg Source: https://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: ? Contributors: ? Original artist: ? • File:Folder_Hexagonal_Icon.svg Source: https://upload.wikimedia.org/wikipedia/en/4/48/Folder_Hexagonal_Icon.svg License: Cc-bysa-3.0 Contributors: ? Original artist: ? • File:Free_Software_Portal_Logo.svg Source: https://upload.wikimedia.org/wikipedia/commons/6/67/Nuvola_apps_emacs_vector.svg License: LGPL Contributors: • Nuvola_apps_emacs.png Original artist: Nuvola_apps_emacs.png: David Vignoni • File:Free_and_open-source-software_display_servers_and_UI_toolkits.svg Source: https://upload.wikimedia.org/wikipedia/ commons/7/7b/Free_and_open-source-software_display_servers_and_UI_toolkits.svg License: CC BY-SA 3.0 Contributors: Own work Original artist: ScotXW

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• File:Jolla_smartphones.jpg Source: https://upload.wikimedia.org/wikipedia/commons/2/2c/Jolla_smartphones.jpg License: CC BY 2.0 Contributors: Flickr: Jolla smartphone Original artist: pestoverde • File:LAMP_software_bundle.svg Source: https://upload.wikimedia.org/wikipedia/commons/8/82/LAMP_software_bundle.svg License: CC BY-SA 3.0 Contributors: This image includes elements that have been taken or adapted from this: Tux-shaded.svg. Original artist: ScotXW • File:Linus_Torvalds_(cropped).jpg Source: https://upload.wikimedia.org/wikipedia/commons/5/5c/Linus_Torvalds_%28cropped% 29.jpg License: CC-BY-SA-3.0 Contributors: • Linus_Torvalds.jpeg Original artist: • derivative work: thumperward Thumperward'>talk)

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