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The Linux Operating System

     Introduction      History      Linux      Why Linux?      Distros      Open Source      Footnotes      Documents in this Series

©2005 - material compiled by Bob Carnaghi, www.webpointmorpheus.com
Introduction     Top of Page
This collection of documents is a series of information that chronicles the Linux operating system. Please consider that this information is not intended to serve as a technical reference or a computer manual. These documents came about as the result of an intense study over a period of several weeks in preparation for the CompTIA Linux+ exam. This information has come from several sources, as listed:
Also please consider that the information contained in these pages is not assembled in an empirical manner. The information does not necessarily prepare the reader to become a 'kernel hacker' or a software developer. The information is offered as stand alone bits and pieces, to be taken as it exists, and integrated into the working knowledge base of the reader. The study of this information had for the author a desired goal of Linux+ certification, and worked to satisfy many strands of unresolved curiosity.
This document gives some background information on the Linux operating system. The information offered here will serve as a basis for the rest of the documents that follow. The birth of the Linux operating system affects its development and continuation today, and the trend will likely continue into the future. You will find below information on Linux history, Open Source Software, popular Linux distribution, and other tidbits.
Linux Operating System Early History     Top of Page
The Linux operating system has as it's most central moment the development of the first Linux kernel by Linus Torvalds in 1991. The impetus for that development was a history of the UNIX operating system that began in the 1960's, and matured through Bell AT&T Labs1 and many other 'hacker'2 type programmers. The UNIX system was (and still is) built from proprietary code, which means that the source code is not available to the general developer.
There were legal hassles in the early days of the UNIX operating system, and the code was released to several universities, one being the University of California at Berkley. From this beginning was created the BSD (Berkley Software Distribution). Typically, UNIX was used by large corporations on main frame computers which were accessed by 'dumb terminals'. The software was also distributed to Hewlett-Packard (HP-UX), IBM (AIX), and Sun Microsystems (Solaris), which created their own flavors of UNIX as listed.
Linus Torvalds was a Finnish student who was working on an improvement to the MINIX3 operating system, and developed the first Linux kernel as a university project. In effect, Linus was a rallying point whose time had come. He created his project and published it under the GNU license thereby paving the way for others to further improve the code. The rest, as they say, is history.
What Exactly is Linux?     Top of Page
The short answer: Linux is a computer operating system. An operating system is a collection of software that integrates human action with the hardware of the computer. More specifically, the actual essence of Linux is the kernel, which is the portion of the operating system software that sits between the user/user software and the computer hardware. There are several distributions of Linux, and they all have in common the Linux kernel. Further, Linux (as was UNIX) is a multi-tasking, multi-user, multi-processor capable kernel. What this means is that there can be several tasks or processes initiated and being used by several different users in action on a single machine (which may have more than one processor) at any given moment.
Why Use Linux?     Top of Page
One would be tempted to ask Why all the hype about Linux? Also, Why should I use Linux? What's in it for me? These are good questions. Most often, computer users make a choice - perhaps early on in their computing experience - which direction to go. While it's difficult to put a hard definition to the typical Linux/Open Source type person, there are some general guidelines. Some Linux users are politically motivated. They believe (generally) in a decentralized government system, or a non-capitalistic economy, and the Open Source approach fits well here. Others are more technically inclined, and the temptation to 'goof with the machine' are tempting beyond restraint. There are other reasons and motivations as well. Whatever may be ones intent, the Open Source system is strong, and the trend is likely to continue. In addition to the Open Source Linux operating systems that are available, the amount of software and other add-ons that are available are overwhelming. Among these are the following:
  • Scientific and Engineering Applications
  • Software development and emulation
  • Web server, browser, SSL, e-commerce, DNS, etc.
  • Desktop applications: word processors, spreadsheets, database applications, etc.
  • Graphics applications
  • Online database applications: MySQL, PostgreSQL, etc.
  • Security Applications
  • VPN systems, Router capability, Beowulf clustering software, etc.
  • There's more...
One would be tempted to think Is there really a free lunch? The answer is yes and no. On the yes side, there is an astounding network of support documentation and communities available for Open Source Software. Also, the number of FAQs and HOW-TOs are immense. One of the concepts involved is TCO - Total Cost of Ownership. This is the total cost of owning an object that includes what often come to be hidden costs at purchase time:
  • Maintenance costs
  • Educational costs
  • Upgrade costs
  • Transition costs
  • Production (loss) costs
  • Additional unforeseen costs
In general, if one is the type of person or collection of people who can take responsibility, don't mind rolling up their sleeves and digging into the workings, Linux & Open Source is the way to go. If not, then it's probably best to pay the piper, and go with a guaranteed, warranted solution.
Linux Distributions     Top of Page
A distribution of Linux is defined as a collection of software and applications that use the Linux kernel. What defines a specific distribution are the software packages that are included in the distribution installation. There about 250 different registered Linux distributions which are all running the same kernel (see link for details). Most typically, each distribution of Linux is tailored to perform a specific function or set of functions, or is targeted to a specific user set, and this defines the purpose of the distribution. Following this intent, the software packages and the capability of services offered by a specific distribution are what makes that distribution unique. Listed below are some of the most popular distriutions of Linux:
  • DistroWatch - Stay in touch with the current Linux & Open Source trends
  • Red Hat Linux - The most popular Linux distro
  • Fedora Core Linux - Published by Red Hat
  • Knoppix - CD bootable OS for use in emergencies or on a foreign computer
  • Slax - The portable OS
  • SuSE Linux - A popular European distro with excellent options and features
  • Debian - Free Linux Distro
  • TurboLinux - by Pacific Hitech (popular in Asia) the leader in clustering technology
  • BlueCat - distributed by Lynuxworks, tailored for embedded device development
  • Caldera OpenLinux - an open source OS (workstation or server) that comes with optional support from Caldera
  • Debian - a multi-platform distro that is favored by advanced users due to limited support
  • Gentoo - a not-so-popular easy-to-install OS with some nice features
  • Hard Hat Linux - the leading Linux distro for embedded applications
  • KRUD - a custom Red Hat Linux based distro that focuses on security and automatic updates
  • Slackware - a UNIX compliant distro that works across several platforms
  • Dream Linux - nice, sleek interface
  • Yellow Dog Linux - based on Redhat 7.0, installs only to PowerPC platform
  • System Rescue CD - a collection of excellent utilities
  • Trinity Rescue Kit

  • ***** Mini Distros *****
  • Astaro - light, security-oriented version
  • KYZO - LinuxROM Flash ROM OS
  • LEM - Mandrake based light install
  • NetMAX - Red Hat based custom distro
  • DSL - Damn Small Linux
Open Source Projects     Top of Page
What is Open Source Software (OSS)? Is it truly open, or are there some forms of stipulations and regulations? These questions are good to ponder when becoming familiar with Open Source Software. Linux is published under the GNU Public License (GPL) which is a product of the Free Software Foundation. This license stipulates that the source code for a system of software is provided free of charge, and can be modified, only if the software created in the process is also provided free of charge. This ensures that a system of software always remains free to the public. An additional type, albeit less common, is the artistic license. This license stipulates that software source code is provided and can be altered only at the discretion of the original author. See the License Types at the Free Software Foundation for more details.

Types of Software
Type Parameters & Implications
Open Source Software that is available free of charge along with the source code for the software. This does not mean that there is no license restriction. Most Open Source Software is published under the GNU license.
Closed Source Software that does not offer the source code. Although this software is sometimes offered for free, it is typically created and marketed for a profit and can often be expensive.
Freeware Closed source software that is distributed for free.
Shareware Closed source software that is distributed with a time or other type of limitation, after which a fee is typically required.

Additional     Top of Page
The website process, the way the web works, Search Engines, and other web & internet concepts are often very confusing, especially for the non-technical person. webpointmorpheus has assembled several documents hoping to simplify these topics. This series of documents are the result of a consistent set of questions posed by current, past, and potential webpointmorpheus clientele. The documents are listed below, and are available in printable/downloadable .pdf form.
Footnotes     Top of Page
  1. The UNIX operating system has a long, deep, and rich history. The history of UNIX is intertwined among computer icons such as Ken Thompson and Dennis Ritchie, Bell Labs, MULTICS, MIT, General Electric, the C programming language, and many more nameless hard working individuals and technology. See the Bell Labs version of UNIX history for further details.
  2. The term 'hacker' in computer programming circles means a person who works at, programs, or expands their knowledge of a computer. This term is to be distinguished from 'cracker' (parallel 'safe cracker') which defines a person who creates, uses, or imposes computer knowledge and programming talents for illegal, immoral, or unethical intent or gain. It is the opinion of this author (albeit possibly slanted) that the term 'hacker' has a severly misunderstood context. For clarification or further understanding, please see The New Hacker's Dictionary
  3. MINIX was a small educational version of UNIX that was developed for the Intel86 platform. Read about or download MINIX.
 
  1. Introduction and History
  2. Installation, Advanced Installation, and Usage
  3. The Linux Kernel and the Boot Process
  4. Filesystems - Management & Administration
  5. The BASH and Other Shells
  6. System Initialization and the X Environment
  7. Linux Processes
  8. Linux Administration, Peripherals, and Hardware
  9. Software Installation and Management
  10. Backups and Log Files
  11. Performance and Problems
  12. Network Configuration
  13. Security
  14. Key Linux Commands
  15. Essential Linux Definitions
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