Linux
Linux is a Unix-like and mostly POSIX-compliant computer operating system assembled under the model of free and open source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on 5 October 1991 by Linus Torvalds. The Free Software Foundation uses the name GNU/Linux, which has led to some controversy.
Linux was originally developed as a free operating system for Intel x86-based personal computers. It has since been ported to more computer hardware platforms than any other operating system. It is a leading operating system on servers and other big iron systems such as mainframe computers and supercomputers. More than 95% of the world's 500 fastest supercomputers run some variant of Linux, including all the 44 fastest. 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 mobile phones, tablet computers, network routers, facility automation controls, televisions and video game consoles. Android, which is a widely used operating system for mobile devices, is built on top of the Linux kernel.
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 licenses such as the GNU General Public License. Typically, Linux is packaged in a format known as a Linux distribution for desktop and server use. Some popular mainstream Linux distributions include Debian, Ubuntu, Linux Mint, Fedora, Arch Linux, and the commercial Red Hat Enterprise Linux and SUSE Linux Enterprise Server. 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.
A distribution oriented toward desktop use will typically include X11, Wayland or Mir as the windowing system, and an accompanying desktop environment such as GNOME or the KDE Software Compilation. Some such distributions may include a less resource intensive desktop such as LXDE or Xfce, for use on older or less powerful computers. A distribution intended to run as a server may omit all graphical environments from the standard install, and instead include other software to set up and operate a solution stack such as LAMP. Because Linux is freely redistributable, anyone may create a distribution for any intended use.
NSA request
Linus Torvalds, the founder of Linux kernel joked during a LinuxCon keynote 18 September 2013, that the NSA, who is the founder of SELinux, wanted a backdoor in the original kernel. However later, Linus' father, Member of the European Parliament (MEP), revealed that the NSA actually did this.
When my oldest son [Linus Torvalds] was asked the same question: “Has he been approached by the NSA about backdoors?” he said “No”, but at the same time he nodded. Then he was sort of in the legal free. He had given the right answer, [but] everybody understood that the NSA had approached him. -- Nils Torvalds, LIBE Committee Inquiry on Electronic Mass Surveillance of EU Citizens - 11th Hearing, 11 November 2013
