Technically speaking, Linux is a kernel. The term "kernel" properly refers to the system software which provide a hardware abstraction layer, disk and filesystem control, multi-tasking, load-balancing, networking and security enforcement. A kernel is not a complete operating system.
Complete systems built around the Linux kernel use the GNU System which provides a shell, utilities, libraries, compilers and tools, as well as miscellaneous programs such as the Emacs editor. For this reason, Richard Stallman of the GNU Project asks users to refer to the entire system as GNU/Linux. Some people do; most do not.
Most systems also include tools and utilities from BSD backgrounds and typically use XFree86 to provide a GUI interface.
Today Linux is a [hybrid monolithic kernel]?. [Device drivers]? and kernel extensions typically run in [ring 0]?, with full access to the hardware, although some run in [user space]?. Unlike standard monolithic kernels, [device drivers]? are easily configured as modules, and loaded or unloaded while running the system. Also unlike standard monolithic kernels, device drivers can be pre-empted under certain conditions. This latter feature was added to correctly handle [hardware interrupts]?, and to improve support for [symmetric multiprocessing]?.
The fact that Linux is not a micro-kernel? was the topic of a famous flame war between Linus and Andy Tanenbaum, a summary of which can be found at http://www.dina.dk/~abraham/Linus_vs_Tanenbaum.html
While Linus Torvalds didn't originally set out to make Linux a portable operating system, it has evolved in that direction. Linux is now in fact one of the most widely ported operating system kernels, running on systems as diverse as the iPaq? (a handheld computer) to the [IBM S/390]? (a massive, hugely expensive mainframe).
However, it is important to note that Linus's efforts were also directed successfully at a different sort of portability. Portability, according to Linus, was the ability to easily compile applications from a variety of sources on his system; thus Linux originally became popular in part because it required the least effort to get everybody's favorite GPL'd and other open source applications running.
Initially, Torvalds released Linux under a license which forbade any commercial exploitation. This was soon changed to the GNU General Public License (version 2 exclusively). This license allows distribution and even sale of possibly modified versions of Linux but requires that all those copies be released under the same license and be accompanied by source code.
A complete Linux Operating System (a "Linux distribution") is a collection of free and sometimes non-free software created by individuals, groups and organizations from around the world and having the Linux kernel at its core. Companies such as Red Hat, SuSE, MandrakeSoft?, as well as the community Debian project, compile the software and provide it as a complete system ready to install and use.
Linux distributions started to enjoy limited popularity in the mid to late 1990s as a free alternative to the Microsoft Windows operating systems and MacOS on the desktop, mostly among people used to Unix from work or school. It has proven more popular in the server market, primarily for Web and database servers.
General Purpose Linux Distributions:
Some groups compile special purpose Linux distributions as turnkey firewalls, for embedded systems, and for other special purposes.
Special Purpose Linux Distributions:
See the distribution list on [The Linux Weekly News].
Linux users, who traditionally had to install and configure their own system, have been more technologically oriented than those of Microsoft Windows and MacOS, often revelling in the tag of "hacker" or "geek". With the adoption of Linux by several large PC manufacturers, computers with Linux distributions pre-installed have become available, and Linux has begun to make slow inroads in the wider desktop market.
With [desktop managers]? such as KDE and GNOME, Linux offers a graphical user interface more like MacOS/Windows than the traditional Unix command line interface, and many no-cost (though not always open source) software packages offer the functionality of programs available on the other desktop operating systems.
The Simple End User Linux organization (SEUL), is an advocacy group for adoption of Linux and end user programs for the OS. (See OS Advocacy).
![[Home]](wikipedia.png)