FOSS A General Introduction/Linux
What is Linux? 
Linux is the most frequently heard FOSS buzzword in the mass media today. However, because of its common usage, the term Linux has been used to refer to broader and broader definitions. It is important to understand the different definitions of Linux to be able to follow the discussions on FOSS.
Linux as the kernel 
Linux was originally the name of the kernel, initially, created by Linus Torvalds. A kernel is the critical center point of an operating system that controls CPU usage, memory management and hardware devices. It also mediates communication between the different programs running within the operating system. There are other FOSS kernels, including the Mach kernel that is the core of some of the BSD distributions.
Kernels are to a certain extent interchangeable. Most FOSS applications will run on a Mach kernel, Linux kernel or even the experimental GNU Hurd kernel, without too much difficulty. However, the kernel type greatly influences performance and the hardware platforms that the FOSS system can run on. For instance, the less mature GNU Hurd kernel can run only on the x86 (PC) architecture. The Linux kernel has been ported to run on almost any computing architecture, including the PlayStation 2 , mainframes and embedded devices.
Linux as a distribution 
The more common usage of Linux today refers to a Linux distribution, which includes far more than the kernel. The Linux distribution (sometimes referred to as the GNU/Linux distribution in recognition of the GNU Project’s significant contribution) contains the Linux kernel at its heart and all the FOSS components required to produce full operating system functionality. This includes the system libraries, GUI, various databases, web servers, email utilities, and others. These same components are also often found on other FOSS and even on proprietary operating systems. For instance, XFree86 is the default GUI foundation in Linux and BSD. XFree86 is also used on proprietary Unix systems such as Solaris, HP-UX and IBM’s AIX system.
Reports that say “Munich May Opt for Linux After All” refer to the Linux distribution, including word processing, printing and email software. Even though the Linux kernel forms less than 0.25 percent (binary file size) of a Linux distribution, its functionality is critical enough to allow the entire distribution to be called Linux.
There is no single Linux distribution. While all distributions contain the Linux kernel at its heart, the FOSS applications included and the configurations supported vary. There are multiple commercial distributions, several freely available, and numerous customized distributions that are targeted to the unique needs of different users. While the FOSS contents of different Linux distributions are mostly identical, they are optimized for different uses such as for high-end servers, user-friendly desktops or even embedded systems. Localized distributions at a minimum include the fonts, input methods and menu translations necessary to use the software in the regional language.
Is Linux FOSS? 
The Linux kernel is FOSS, licensed under the GNU General Public License. However, different distributions of Linux contain different components, some of which are not FOSS. For example, the German SuSE Linux distribution includes the non-FOSS YaST (Yet another Setup Tool) installation program.
Where can one obtain Linux? 
FOSS, in binary and source code format, is free and downloadable from the Internet. The Linux kernel itself can be downloaded from http://www.kernel.org and other applications from their respective websites. However, most users tend to obtain distributions of Linux. The following is a table of some of the most popular distributors of Linux:
- Download time: The Linux operating system and complementary software involve large files and long download times. A standard 56kbps modem would take at least 45 days to download a standard 3 CD distribution. Vendors also provide bundled software—browsers, server applications, office suite, etc.—that saves the users from the tedious work of hunting and downloading individual software packages.
- Installation and compiling time: Many FOSS packages are downloadable only as source code. Users are required to compile and install the software themselves, assuming they are competent enough to do so. On a slow computer, compilation of source code may take days or even weeks. Vendor distributions of Linux often come precompiled and packaged with an easy installation system that takes less than an hour to install on most modern systems.
- Quality assurance: Vendors typically perform extensive testing to ensure that all of the components work well together. Since FOSS projects are developed independently, there is always the chance that changes in one package have outdated another package. Vendors resolve these dependencies for the user, supplying an integrated package that works “out of the box”.
- Learning time: Vendors provide manuals and publish reference material (for sale) for their products, making Linux much easier for the average user to learn.
- “Linux for Playstation 2 Community” [home page online]; available from http://playstation2-linux.com/; Internet; accessed on November 9, 2003.
- Proffitt, Brian, “Munich May Opt for Linux After All”, 26 May 2003, Linuxtoday.com [home page online]; available from http://linuxtoday.com/infrastructure/2003052600126NWSWPB; Internet; accessed on November 9, 2003.
- “Debian GNU/Linux -- The Universal Operating System“ [home page online]; available from http://www.debian.org; Internet; accessed on November 9, 2003.