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The Gnu Linux Connection
An operating system is the low-level software that schedules tasks, allocates storage, and handles the interfaces to peripheral hardware, such as printers, disk drives, the screen, keyboard, and mouse. An operating system has two main parts: the kernel and the system programs. The kernel allocates machine resources, including memory, disk space, and CPU (page 869) cycles, to all other programs that run on the computer. The system programs perform higher-level housekeeping tasks, often acting as servers in a client/server relationship. Linux is the name of the kernel that Linus Torvalds presented to the world in 1991 and that many others have worked on since then to enhance, stabilize, expand, and make more secure.
The History of Gnu Linux
This section presents some background on the relationship between GNU and Linux.
Fade to 1983
Richard Stallman (www.stallman.org) announces the GNU Project for creating an operating system, both kernel and system programs, and presents the GNU Manifesto, which begins as follows:
Some years later Stallman added a footnote to the preceding sentence when he realized that it was creating confusion:
In the manifesto, after explaining a little about the project and what has been accomplished so far, Stallman continues:
Next Scene, 1991
The GNU Project has moved well along toward its goal. Much of the GNU operating system, except for the kernel, is complete. Richard Stallman later writes:
Today the GNU "operating system" runs on top of the FreeBSD (www.freebsd.org) and NetBSD (www.netbsd.org) kernels with complete Linux binary compatibility and on top of Hurd pre-releases and Darwin (developer.apple.com/darwin) without this compatibility.
The Code is Free
The tradition of free software dates back to the days when UNIX was released to universities at nominal cost, which contributed to its portability and success. This tradition died as UNIX was commercialized and manufacturers regarded the source code as proprietary, making it effectively unavailable. Another problem with the commercial versions of UNIX related to their complexity. As each manufacturer tuned UNIX for a specific architecture, it became less portable and too unwieldy for teaching and experimentation.
Two professors created their own stripped-down UNIX look-alikes for educational purposes: Doug Comer created XINU (www.cs.purdue.edu/research/xinu.html) and Andrew Tanenbaum created MINIX (www.cs.vu.nl/~ast/minix.html). Linus Torvalds created Linux to counteract the shortcomings in MINIX. Every time there was a choice between code simplicity and efficiency/features Tanenbaum chose simplicity (to make it easy to teach with MINIX), which meant that this system lacked many of features people wanted. Linux goes in the opposite direction.
You can obtain Linux at no cost over the Internet. You can also obtain the GNU code via the U.S. mail at a modest cost for materials and shipping. You can support the Free Software Foundation by buying the same (GNU) code in higher-priced packages, and you can buy commercial packaged releases of Linux (called distributions) that include installation instructions, software, and support.
Linux and GNU software are distributed under the terms of the GNU General Public License (GPL, www.gnu.org/licenses/licenses.html). The GPL says you have the right to copy, modify, and redistribute the code covered by the agreement. If you redistribute the code, you must also distribute the same license with the code, making the code and the license inseparable. If you get the source code off the Internet for an accounting program that is under the GPL, modify the code, and then redistribute an executable version of the program, you must also distribute the modified source code and the GPL agreement with it. Because this is the reverse of the way a normal copyright works (it gives rights instead of limiting them), it has been termed a copyleft. (This paragraph is not a legal interpretation of the GPL; it simply gives you an idea of how it works. Refer to the GPL itself when you want to make use of it.)
Two key words for Linux are "Have Fun!" These words pop up in prompts and documentation. The UNIX now Linux culture is steeped in humor that can be seen throughout the system. For example, less is more GNU has replaced the UNIX paging utility named more with an improved utility named less. The utility to view PostScript documents is named ghostscript, and one of several replacements for the vi editor is named elvis. While machines with Intel processors have "Intel Inside" logos on their outside, some Linux machines sport "Linux Inside" logos. And Torvalds himself has been seen wearing a T-shirt bearing a "Linus Inside" logo.
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