   #copyright

Linux

2007 Schools Wikipedia Selection. Related subjects: Software

   CAPTION: Linux

   Tux the penguin, mascot of Linux
   Tux the penguin, based on an image created by Larry Ewing in 1996, is
   the mascot of Linux.
   OS family: Unix-like
   Latest stable release: 2.6.18.3 ( kernel) / November 19, 2006
   Kernel type: Monolithic kernel
   License: GNU General Public License
   Working state: Current

   Linux (also known as GNU/Linux) is a Unix-like computer operating
   system. It is one of the most prominent examples of open source
   development and free software; its underlying source code is available
   for anyone to use, modify, and redistribute freely.

   Initially developed and used primarily by individual enthusiasts on
   personal computers, Linux has since gained the support of corporations
   such as IBM, Sun Microsystems, Hewlett-Packard, and Novell, Inc., and
   has risen to prominence as an operating system for servers; eight of
   the ten most reliable internet hosting companies now run Linux on their
   web servers.

   Linux has been more widely ported to different computing platforms than
   any other operating system. It is used in devices ranging from
   supercomputers to mobile phones, and is gaining popularity in the
   personal computer market.

History

Early

   Linus Torvalds, creator of the Linux kernel.
   Enlarge
   Linus Torvalds, creator of the Linux kernel.

   In 1983, Richard Stallman founded the GNU Project, with the goal of
   developing a complete Unix-like operating system composed entirely of
   free software. By the beginning of the 1990s, GNU had produced or
   collected most of the necessary components of this system — libraries,
   compilers, text editors, a Unix shell — except for the core component,
   the kernel. The GNU project began developing a kernel, the GNU Hurd, in
   1990, based on the Mach microkernel, but the development of this
   Mach-based design proved difficult and proceeded slowly.

   Meanwhile, in 1991, another kernel was begun as a hobby by Finnish
   university student Linus Torvalds while attending the University of
   Helsinki. Torvalds originally used Minix on his own computer, a
   simplified Unix-like system written by Andrew Tanenbaum for teaching
   operating system design. However, Tanenbaum did not permit others to
   extend his operating system, leading Torvalds to create a replacement
   for Minix.

   Originally, Torvalds called his kernel "Freax" for "free" and "freak"
   and with the often-used X in the names of Unix-like systems. The name
   "Linux" was coined by Ari Lemmke, who administered an FTP server
   belonging to the Finnish University Network; he invented the name Linux
   for the directory from which Torvalds' project was first available for
   download.
   A graphic history of Unix systems. Linux is a Unix-type system but its
   source code does not descend from the original Unix.
   Enlarge
   A graphic history of Unix systems. Linux is a Unix-type system but its
   source code does not descend from the original Unix.

   At first a computer running Minix was necessary in order to configure
   and install Linux. Initial versions of Linux also required another
   operating system to be present in order to boot from a hard disk, but
   soon there were independent boot loaders such as LILO. The Linux system
   quickly surpassed Minix in functionality; Torvalds and other early
   Linux kernel developers adapted their work for the GNU components and
   user-space programs to create a complete, fully functional, and free
   (as in freedom) operating system.

   Today, Torvalds continues to direct the development of the kernel,
   while other subsystems such as the GNU components continue to be
   developed separately. Other groups and companies combine and distribute
   these components with additional application software in the form of
   Linux distributions.

Linux and the GNU Project

   Richard Stallman, founder of the GNU project for a free operating
   system.
   Enlarge
   Richard Stallman, founder of the GNU project for a free operating
   system.

   The goal of the GNU project is to produce a Unix-compatible operating
   system consisting entirely of free software, and most general-purpose
   Linux distributions rely on GNU libraries and tools written to that
   effect. The Free Software Foundation views these Linux distributions as
   "variants" of the GNU system, and asks that such operating systems be
   referred to as GNU/Linux or a Linux-based GNU system. While some
   distributions make a point of using the combined form - notably Debian
   GNU/Linux - its use outside of the enthusiast community is limited, and
   Linus Torvalds has said that he finds calling Linux in general
   GNU/Linux "just ridiculous". The distinction between the Linux kernel
   and distributions based on it is a source of confusion to many
   newcomers, and the naming remains controversial.

SCO litigation

   In March 2003, the SCO Group filed a lawsuit against IBM, claiming that
   IBM had contributed portions of SCO's copyrighted code to the Linux
   kernel in violation of IBM's license to use Unix. Additionally, SCO
   sent letters to a number of companies warning that their use of Linux
   without a license from SCO may be actionable, and claimed in the press
   that they would be suing individual Linux users. This controversy has
   involved lawsuits by SCO against DaimlerChrysler (dismissed in 2004),
   and AutoZone, and by Red Hat and others against SCO. Furthermore,
   whether SCO even owns the relevant Unix copyrights is currently
   disputed by Novell.

   As per the Utah District Court ruling on July 3, 2006; 182 claims out
   of 294 claims made by SCO against IBM have been dismissed.

   SCO's claims have varied widely. As of 2006, no proof of SCO's claims
   of copied code in Linux has been provided.

Portability

   The Linux kernel was originally designed only for Intel 80386
   microprocessors, but now supports a wide variety of computer
   architectures. Linux is one of the most widely ported operating
   systems, running on a diverse range of systems from the hand-held
   ARM-based iPAQ to the mainframe IBM System z9. Specialized
   distributions exist for less mainstream architectures. The ELKS kernel
   fork can run on Intel 8086 or 286 16-bit microprocessors. There are
   even ports to atypical devices such as iPods and consoles.

Copyright, licensing, and the Linux trademark

   The Linux kernel and most GNU software are licensed under the GNU
   General Public License. The GPL requires that all distributed source
   code modifications and derived works also be licensed under the GPL,
   and is sometimes referred to as a "share and share-alike" or "
   copyleft" license. In 1997, Linus Torvalds stated, "Making Linux GPL'd
   was definitely the best thing I ever did." Other software may use other
   licenses; many libraries use the GNU Lesser General Public License
   (LGPL), a more permissive variant of the GPL, and the X Window System
   uses the MIT License.

   In the United States, the name Linux is a trademark registered to Linus
   Torvalds. Initially, nobody registered it, but on August 15, 1994,
   William R. Della Croce, Jr. filed for the trademark Linux, and then
   demanded royalties from Linux distributors. In 1996, Torvalds and some
   affected organizations sued to have the trademark assigned to Torvalds,
   and in 1997 the case was settled. The licensing of the trademark is now
   handled by the Linux Mark Institute. Torvalds has stated that he only
   trademarked the name to prevent someone else from using it, but was
   bound in 2005 by United States trademark law to take active measures to
   enforce the trademark. As a result, the LMI sent out a number of
   letters to distribution vendors requesting that a fee be paid for the
   use of the name, and a number of companies have complied.

Pronunciation

   In 1992, Torvalds explained how he pronounces the word Linux ( IPA:
   /'lɪnʉks/)

   “ 'li' is pronounced with a short [ee] sound: compare prInt, mInImal
      etc. 'nux' is also short, non-diphthong, like in pUt {IPA /ʊ/}. It's
     partly due to minix: linux was just my working name for the thing, and
       as I wrote it to replace minix on my system, the result is what it
                        is... linus' minix became linux.                   „

                  —Linus Torvalds, comp.os.linux newsgroup

   An audio file of Torvalds saying "Hello, this is Linus Torvalds, and I
   pronounce Linux as Linux" can be found here. Note that in English,
   "Linux" and "Minix" are usually pronounced with a short i ( IPA: /ɪ/)
   sound that is different from Torvalds' Finland Swedish pronunciation of
   these words.

Development

   More Than a Gigabuck: Estimating GNU/Linux's Size, a 2001 study of Red
   Hat Linux 7.1, found that this distribution contained 30 million source
   lines of code. Using the Constructive Cost Model, the study estimated
   that this distribution required about eight thousand man-years of
   development time. According to the study, if all this software had been
   developed by conventional proprietary means, it would have cost about
   1.08 billion dollars (year 2000 U.S. dollars) to develop in the United
   States.

   The majority of the code (71%) was written in the C programming
   language, but many other languages were used, including C++, Lisp,
   assembly language, Perl, Fortran, Python and various shell scripting
   languages. Slightly over half of all lines of code were licensed under
   the GPL. The Linux kernel was 2.4 million lines of code, or 8% of the
   total.

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

Distributions

   A KDE desktop on the SUSE Linux distribution.
   Enlarge
   A KDE desktop on the SUSE Linux distribution.

   Linux is predominantly used as part of a Linux distribution (commonly
   called a "distro"). These are compiled by individuals, loose-knit
   teams, and commercial and volunteer organizations. They commonly
   include additional system and application software, an installer system
   to ease initial system setup, and integrated management of software
   installation and upgrading. Distributions are created for many
   different purposes, including computer architecture support,
   localization to a specific region or language, real-time applications,
   and embedded systems, and many deliberately include only free software.
   Currently, over three hundred distributions are actively developed,
   with about a dozen distributions being most popular for general-purpose
   use.

   A typical general-purpose distribution includes the Linux kernel, some
   GNU libraries and tools, command-line shells, the graphical X Window
   System and an accompanying desktop environment such as KDE or GNOME,
   together with thousands of application software packages, from office
   suites to compilers, text editors, and scientific tools.

Desktop usage

   A GNOME desktop running from the GNOME LiveCD.
   Enlarge
   A GNOME desktop running from the GNOME LiveCD.

   The high level of access granted to Linux's internals has led to Linux
   users traditionally tending to be more technologically oriented than
   users of Microsoft Windows and Mac OS, sometimes revelling in the tag
   of " hacker" or " geek". Linux and other free software projects have
   been frequently criticized for not going far enough to ensure ease of
   use.

   This stereotype has begun to be dispelled in recent years. Linux may
   now be used with a user interface that is very similar to those running
   on other operating systems. However users may have to switch to
   alternative application software, and there are often fewer "known"
   software choices (as in the case of computer games) but there exist
   replacements for all general-purpose software, and general applications
   like spreadsheets, word processors, and browsers are available for
   Linux in profusion. Additionally, a growing number of proprietary
   software vendors are supporting Linux, and compatibility layers such as
   Wine or NdisWrapper allow some Windows application software and drivers
   to be used on Linux without requiring the vendor to adapt them.

   Linux's roots in the Unix operating system mean that in addition to
   graphical configuration tools and control panels available for many
   system settings and services, plain-text configuration files are still
   commonly used to configure the OS and can readily be made accessible
   (or not) to users, at the administrator's will.

   The Berlin-based organization Relevantive concluded in 2003 that the
   usability of Linux for a set of desktop-related tasks was "nearly equal
   to Windows XP." Since then, there have been numerous independent
   studies and articles which indicate that a modern Linux desktop using
   either GNOME or KDE is on par with Microsoft Windows in a business
   setting.

Enterprise usage

   Linux has historically been used mainly as a server operating system,
   but its low cost, flexibility, and Unix-like architecture make it
   suitable for a variety of applications. Linux is the cornerstone of the
   " LAMP" server-software combination (Linux, Apache, MySQL,
   Perl/PHP/Python) which has achieved popularity among developers, and
   which is one of the more common platforms for website hosting.

   Due to its low cost and its high configurability, Linux is often used
   in embedded systems such as television set-top boxes, mobile phones,
   and handheld devices. Linux has become a major competitor to the
   proprietary Symbian OS found in many mobile phones, and it is an
   alternative to the dominant Windows CE and Palm OS operating systems on
   handheld devices. The popular TiVo digital video recorder uses a
   customized version of Linux. Several network firewall and router
   standalone products, including several from Linksys, use Linux
   internally, using its advanced firewalling and routing capabilities.

   Linux is increasingly common as an operating system for supercomputers.
   For example, in the November 2005 TOP500 list of supercomputers, seven
   of the top ten supercomputers in the world, including the two fastest,
   ran Linux. Of the 500 systems, 371 (74.2%) ran Linux.

Market share and uptake

   According to the market research company IDC, 25% of servers and 2.8%
   of desktop computers ran Linux as of 2004. Proponents and analysts
   attribute the success of Linux to its security, reliability, low cost,
   and freedom from vendor lock-in. The frictional cost of switching and
   lack of support for some hardware and many application programs
   designed for Windows, especially games or uncommon business software,
   are two important factors inhibiting adoption.

   The Linux market is rapidly growing and the revenue of servers,
   desktops, and packaged software running Linux is expected to exceed
   $35.7 billion by 2008. The actual installed user base may be higher
   than indicated by this figure, as most Linux distributions and
   applications are freely available and redistributable.

   The paper Why Open Source Software / Free Software (OSS/FS)? Look at
   the Numbers! identifies many quantitative studies of open source
   software on topics including market share and reliability, with many
   studies specifically examining Linux.

Installation

   The most common method of installing Linux on a personal computer is by
   booting from a CD-ROM that contains the installation program and
   installable software. Such a CD can be burned from a downloaded ISO
   image, purchased alone for a low price, obtained as part of a box set,
   or in a few cases shipped for free by request. A box set may also
   include manuals and additional proprietary software. Mini CD images
   allow Linux to be installed from a disk with a small form factor.

   As with servers, personal computers that come with Linux already
   installed are available from vendors including Hewlett-Packard and
   Dell, although generally only for their business desktop line.

   Alternatives to traditional desktop installation include thin client
   installation and running directly from a Live CD. In a thin client
   installation, the operating system is loaded and run from a centralised
   machine over a network connection. In a Live CD setup, the computer
   boots the entire operating system from CD without first installing it
   on the computer's hard disk.

   On embedded devices, Linux is typically held in the device's firmware
   and may or may not be consumer-accessible.

Programming on Linux

   The GNU Compiler Collection (GCC) is the standard compiler family for
   most Linux systems. Amongst others, GCC provides frontends for C, C++
   and Java. Most distributions come installed with interpreters for Perl,
   Python and other scripting languages, and several now include C# via
   the Mono project.

   There are a number of Integrated development environments available
   including MonoDevelop, KDevelop, Anjuta, NetBeans, and Eclipse while
   the traditional editors Emacs and Vim remain popular.

   The two main widget toolkits used for contemporary GUI programming are
   Qt and the Gimp Toolkit, known as GTK+.

   As well as these free and open source options, there are proprietary
   compilers and tools available from a range of companies such as Intel,
   PathScale, Micro Focus COBOL,, Franz Inc, and the Portland Group.

Support

   Technical support is provided by commercial suppliers and by other
   Linux users, usually in online forums, IRC, newsgroups, and mailing
   lists. Linux User Groups have traditionally been organized to provide
   support for Linux in specific cities and regions.

   The business model of commercial suppliers is generally dependent on
   charging for support, especially for business users. A number of
   companies 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.

   Retrieved from " http://en.wikipedia.org/wiki/Linux"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
