Linux Architecture - History

History

See also: History of Linux

In April 1991, Linus Torvalds, a 21-year-old student at the University of Helsinki, Finland started working on some simple ideas for an operating system. He started with a task switcher in Intel 80386 assembly language and a terminal driver. On 25 August 1991, Torvalds posted the following to comp.os.minix, a newsgroup on Usenet:

I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since April, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).

I've currently ported bash(1.08) and gcc(1.40), and things seem to work. This implies that I'll get something practical within a few months Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT portable (uses 386 task switching etc), and it probably never will support anything other than AT-harddisks, as that's all I have :-(.

It's mostly in C, but most people wouldn't call what I write C. It uses every conceivable feature of the 386 I could find, as it was also a project to teach me about the 386. As already mentioned, it uses a MMU, for both paging (not to disk yet) and segmentation. It's the segmentation that makes it REALLY 386 dependent (every task has a 64Mb segment for code & data - max 64 tasks in 4Gb. Anybody who needs more than 64Mb/task - tough cookies). Some of my "C"-files (specifically mm.c) are almost as much assembler as C. Unlike minix, I also happen to LIKE interrupts, so interrupts are handled without trying to hide the reason behind them.

After that, many people contributed code to the project. 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 operating system, but its own kernel, GNU Hurd, was incomplete and unavailable. The BSD operating system had not yet freed itself from legal encumbrances. Despite the limited functionality of the early versions, Linux rapidly accumulated developers and users.

By September 1991, Linux version 0.01 was released on the FTP server (ftp.funet.fi) of the Finnish University and Research Network (FUNET). 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 had not permitted commercial redistribution.

A newsgroup known as alt.os.linux was started, and on 19 January 1992, the first post to alt.os.linux was made. On 31 March 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 14 March 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 9 June 1996, was followed by additional major versions under the version 2 header:

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

Starting in 2004, the release process changed and new kernels started coming out on a regular schedule every 2-3 months, numbered 2.6.0, 2.6.1, up through 2.6.39.

On 21 July 2011 Linus Torvalds announced the release of Linux 3.0: "Gone are the 2.6. days". The version bump is not about major technological changes when compared to Linux 2.6.39; it marks the kernel's 20th anniversary. The time-based release process remained the same.

As of 2012, the Linux 3.2 release had 14,998,651 lines of code.