Linux is a Unix-like computer operating system family which uses the Linux kernel. Linux is one of the most prominent examples of free software and open source development; typically all the underlying source code can be freely modified, used, and redistributed by anyone.
Predominantly known for its use in servers, it is installed on a wide variety of computer hardware, ranging from embedded devices and mobile phones to supercomputers.
The name "Linux" comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU operating system, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux.
History
The creation of the Linux kernel
In 1991, Torvalds began to work on a non-commercial replacement for MINIX while he was attending the University of Helsinki,[5] which would eventually become the Linux kernel.
Contributions from GNU
Linux was originally dependent on the MINIX user space which, due to license issues complicated distribution. With the user space from GNU freely available, it was in both in the Linux hobbyists and the GNU Project's interest if both could be distributed together. However, at the time Linux had a license that prohibited commercial distribution making it incompatible with the GNU General Public License. In 1992, with version 0.12 of the Linux kernel, Torvalds initiated a switch from his original license to the GPL. Various Linux distributions (Slackware, Debian, Red Hat, and others) combined Linux and GNU code to make a fully functional and free operating system.
Commercial and popular uptake
Today Linux is used in numerous domains, from embedded systems to supercomputers, and has secured a place in server installations with the popular LAMP application stack.Linux use in home desktop and enterprise desktop has been rapidly expanding and now claims a significant share of the desktop market.
Linux has also become popular with the newly founded netbook market, with many devices such as the ASUS Eee PC and Acer Aspire One shipping with customized Linux distributions pre-installed.
Current Development
Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work including kernel modules, libraries, and user applications. Linux vendors and communities combine and distribute the kernel, GNU components, and other components in the form of Linux distributions.
Design
Linux is a modular Unix-like operating system. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Linux uses a monolithic kernel, the Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel.
Much of Linux's higher-level functionality is provided by separate projects which interface with the kernel. The GNU userland is an important part of most Linux systems, providing the shell and Unix tools which carry out many basic operating system tasks. On top these tools form a Linux system with a graphical user interface that can be used, usually running in the X Window System.
User interface
Linux can be controlled by one or more of a text-based command line interface (CLI), graphical user interface (GUI) (usually the default for desktop), or through controls on the device itself (common on embedded machines).
On desktop machines, KDE, GNOME and Xfce are the most popular user interfaces, though a variety of other user interfaces exist. Most popular user interfaces run on top of the X Window System (X), which provides network transparency, enabling a graphical application running on one machine to be displayed and controlled from another.
Other GUIs include X window managers such as FVWM, Enlightenment and Window Maker. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system.
A Linux system typically provides a CLI of some sort through a shell, which is the traditional way of interacting with a Unix system. A Linux distribution specialized for servers may use the CLI as its only interface. A “headless system” run without even a monitor can be controlled by the command line via a protocol such as SSH or telnet.
Most low-level Linux components, including the GNU Userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. A graphical terminal emulator program is often used to access the CLI from a Linux desktop.
Development
A summarised history of Unix-like operating systems showing Linux's origins. Note that despite similar architectural designs and concepts being shared as part of the POSIX standard, Linux does not share any non-free source code with the original Unix or Minix.
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 the best-known and most widely used. Some free and open source software licences are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU GPL, is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU project.
As an operating system underdog competing with mainstream operating systems, Linux cannot rely on a monopoly advantage; in order for Linux to be convenient for users, Linux aims for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX, SUS, ISO and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.
Free software projects, although developed in a collaborative fashion, are often produced independently of each other. However, given that the software licenses explicitly permit redistribution, this provides a basis for larger scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a Linux distribution.
A Linux distribution, commonly called a “distro”, is a project that manages a remote collection of Linux-based software, and facilitates installation of a Linux operating system. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. They include system software and application software in the form of packages, and distribution-specific software for initial system installation and configuration as well as later package upgrades and installs. A distribution is responsible for the default configuration of installed Linux systems, system security, and more generally integration of the different software packages into a coherent whole.
distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list.
There are several technology websites with a Linux focus. Print magazines on Linux often include cover disks including software or even complete Linux distributions.
Although Linux is generally available free of charge, several large corporations have established business models that involve selling, supporting, and contributing to Linux and free software. These include Dell, IBM, HP, Sun Microsystems, Novell, Nokia. There are several corporations which built their entire business around Linux, notably Red Hat.
The free software licenses on which Linux is based explicitly accommodate and encourage commercialization; the relationship between Linux as a whole and individual vendors may be seen as symbiotic. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks. Another business model is to give away the software in order to sell hardware.
Uses
As well as those designed for general purpose use on desktops and servers, distributions may be specialized for different purposes including: computer architecture support, embedded systems, stability, security, localization to a specific region or language, targeting of specific user groups, support for real-time applications, or commitment to a given desktop environment. Furthermore, some distributions deliberately include only free software. Currently, over three hundred distributions are actively developed, with about a dozen distributions being most popular for general-purpose use. Linux is a widely ported operating system. The Linux kernel runs on the most diverse range of computer architectures: in the hand-held ARM-based iPAQ and the mainframe IBM System z9, in devices ranging from mobile phones to supercomputers.Specialized distributions exist for less mainstream architectures. The ELKS kernel fork can run on Intel 8086 or Intel 80286 16-bit microprocessors, while the µClinux kernel 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, PDAs, video game consoles, portable music players, and mobile phones.
0 Comments