Linux

Linux
Larry Ewing, Simon Budig, Garrett LeSage · CC0 · source
Name	Linux
Developer	Linus Torvalds, GNU Project, numerous contributors
Source model	Open source
Kernel type	Monolithic
Userland	GNU, BusyBox, others
Ui	CLI and GUI (via X Window System, Wayland)
License	GPLv2 (kernel)
Working state	Current

Linux. It is a family of Unix-like operating systems based on the Linux kernel, a monolithic kernel first released on September 17, 1991, by Linus Torvalds. Typically packaged as a Linux distribution, which includes the kernel and supporting system software and libraries, many of which are provided by the GNU Project. These distributions are used widely, from embedded devices and supercomputers to servers and desktop computers.

History

The development of the kernel was initiated by Linus Torvalds while he was a student at the University of Helsinki. Inspired by MINIX, an educational system created by Andrew S. Tanenbaum, Torvalds sought to create a free alternative. He announced his project in a famous post to the Usenet newsgroup comp.os.minix in August 1991. The kernel's early growth was fueled by collaboration over the early Internet, with developers contributing code via platforms like FTP and email lists. A pivotal moment was the adoption of the GNU General Public License (GPL) for version 0.12, aligning its legal framework with the Free Software Foundation's GNU Project, which had created many essential components but lacked a working kernel. This combination of the Linux kernel and GNU utilities formed the basis of a complete, free operating system, often called GNU/Linux. Major milestones include its adoption by corporations like IBM and Oracle in the late 1990s, and its dominance in web server markets, famously powering sites like Google and Amazon.

Design and principles

The system is built around a monolithic kernel that handles process control, networking, and access to hardware devices. Unlike microkernels, it runs most services in kernel space for performance, though it supports loadable kernel modules for extensibility. A fundamental principle is its adherence to the Unix philosophy, emphasizing small, modular programs that do one thing well. The kernel is designed to be highly portable, originally written for the Intel i386 architecture but now running on a vast array of platforms including ARM, PowerPC, and RISC-V. The overall system design relies heavily on the GNU Core Utilities, the GNU C Library (glibc), and init systems like systemd or OpenRC for booting and service management. User interfaces are separated, with the kernel interacting with graphical servers like the X Window System or Wayland.

Development and distribution

Kernel development is overseen by Linus Torvalds and a group of key maintainers, including Greg Kroah-Hartman. Contributions flow through a hierarchical model, with patches being merged from subsystem maintainers into the mainline kernel tree hosted on kernel.org. Development follows a time-based release model, with new versions arriving approximately every nine to ten weeks. The kernel source is managed using the Git version control system, also created by Torvalds. End-users typically obtain Linux through distributions, which curate the kernel, software, and provide installers. Major distributions include Red Hat (and its community fork Fedora), SUSE, Debian, and Ubuntu. Specialized distributions exist for various purposes, such as Kali Linux for security, Raspberry Pi OS for embedded use, and Android for mobile devices. Commercial support is offered by companies like Red Hat, Canonical, and IBM.

Applications and uses

It is the dominant operating system in several critical sectors. It powers the vast majority of the world's supercomputers, as tracked by the TOP500 list, and is foundational to cloud infrastructure from providers like AWS, Microsoft Azure, and Google Cloud Platform. The LAMP stack (Linux, Apache, MySQL, PHP) has been a standard for web hosting for decades. In embedded systems, it runs on devices from smart televisions and routers to automotive infotainment systems. The Android mobile operating system, developed by Google, uses a modified Linux kernel, making it the most widely deployed kernel on smartphones. It is also prevalent in server rooms, running critical infrastructure for finance, telecommunications, and scientific research at organizations like NASA and CERN.

Licensing and legal aspects

The kernel is primarily licensed under version 2 of the GNU General Public License (GPLv2), a Copyleft license that guarantees end users the freedom to run, study, share, and modify the software. This license requires that any distributed modified versions must also be released under the same terms. The licensing model has led to significant legal discussions and cases, such as the dispute between the Free Software Foundation and The SCO Group in the early 2000s. Some kernel components, like drivers, may be under different licenses such as the BSD licenses or the LGPL. The use of GNU software throughout most distributions means the overall system is governed by a mix of GPL and other open-source licenses. Compliance with these licenses is a major consideration for commercial distributors and embedded device manufacturers, often managed through tools and processes for tracking software provenance.

Category:Free software Category:Operating systems Category:Software using the GPL license