Linux is an operating system kernel used by a family of Unix-like operating systems. These are popularly termed Linux operating systems and the name is also used for the various Linux distributions built on top of the operating system.

The Linux kernel is released under the GNU General Public License version 2 (GPLv2) and developed by contributors worldwide; Linux is one of the most prominent examples of Open Source software.

The Linux kernel was initially conceived and created by Finnish software engineer Linus Torvalds in 1991. Early on, the MINIX community contributed code and ideas to the Linux kernel. At the time, the GNU Project had created many of the components required for a free software operating system, but its own kernel, GNU Hurd, was incomplete and unavailable. The BSD operating system had not yet freed itself from legal encumbrances. This meant that despite the limited functionality of the early versions, Linux rapidly accumulated developers and users who adopted code from those projects for use with the new operating system. Today the Linux kernel has received contributions from thousands of programmers.

History

In April 1991, Linus Torvalds, then 21 years old, started working on some simple ideas for an operating system. He started with a task switcher in Intel 80386 assembly and a terminal driver. Then, on 26 August 1991, Torvalds posted to comp.os.minix:

After that, many people contributed code to the project. By September 1991, Linux version 0.01 was released. It had 10,239 lines of code. In October 1991, Linux version 0.02 was released.

In December 1991, Linux 0.11 was released. This version was the first to be self-hosted - Linux 0.11 could be compiled by a computer running Linux 0.11. When he released version 0.12 in February 1992, Torvalds adopted the GNU General Public License (GPL) over his previous self-drafted license, which did not permit commercial redistribution.

A newsgroup alt.os.linux was started, and on January 19 1992, the first post to alt.os.linux was made. On March 31 1992, alt.os.linux became comp.os.linux.

The X Window System was soon ported to Linux. In March 1992, Linux version 0.95 was the first to be capable of running X. This large version number jump (from 0.1x to 0.9x) was due to a feeling that a version 1.0 with no major missing pieces was imminent. However, this proved to be somewhat overoptimistic, and from 1993 to early 1994, 15 development versions of version 0.99 appeared.

On March 14 1994, Linux 1.0.0 was released, with 176,250 lines of code. In March 1995, Linux 1.2.0 was released (310,950 lines of code).

Version 2 of Linux, released on June 9, 1996, was followed by additional major versions under the version 2 header:

• January 25 1999 - Linux 2.2.0 was released (1,800,847 lines of code).
• December 18 1999 - IBM mainframe patches for 2.2.13 were published, allowing Linux to be used on enterprise-class machines.
• January 4 2001 - Linux 2.4.0 was released (3,377,902 lines of code).
• December 17 2003 - Linux 2.6.0 was released (5,929,913 lines of code).
• April 16 2008 - Linux 2.6.25 was released (9,232,484 lines of code)."Linux Kernel Data."