Chapter 1 Introduction To Linux Linux+ Guide to Linux Certification Second Edition
Linux+ Guide to Linux Certification, 2e 2 Objectives Describe the origins of the Linux operating system Understand the term Opensource Software Identify the characteristics of various Linux distributions Common uses of Linux in industry today Key features of the Linux operating system
Linux+ Guide to Linux Certification, 2e 3 To understand this diagram we need to discuss some history first. Free Software Foundation AT & T
Linux+ Guide to Linux Certification, 2e 4 What is UNIX It is an operating system which has been commonly used for the past 30 years. It was created in 1969 - long before Microsoft existed. It was the 1st worldwide commercial operating system. Unix has always commonly been used on mainframes. Today it is also commonly being used on PCs. Today it runs the global network, commonly called the Internet 80% of the worlds Internet Web servers are using UNIX. The Internet was built on UNIX. TCP/IP is a native UNIX protocol.
In the beginning . 1960s The American government gave out huge grants to groups willing to do R&D, using their specifications for the needs of the new computer industry. 1965 3 companies AT&T, General Electric & MIT were jointly working on a project to design a new OS called Multics Which would provide multi-user, multi-tasking, multi-processor functions & would make use of a multi-level (hierarchical) file system 1969 - AT&T was unhappy with the progress. The development and the relevant costs were all unsatisfactory so they dropped out of the combined project.
BUT . The AT&T programmers in the group held onto a copy of Multics. They were Ken Thompson, Dennis Ritchie They put Multics on an unused mainframe - Digital PDP-7 AND they also renamed it to UNIX.
Linux+ Guide to Linux Certification, 2e 7 1970s - Unix History & Development 1971 -they developed the 1 st UNIX user program Which was as a text processing tool for the patent department at Bell Labs. the ability for user word processing and formatting. This 1 st real use of UNIX justified further R&D to be supported by AT&T for the UNIX programming group.
Linux+ Guide to Linux Certification, 2e 8 Unix was the first OS to supply: UNIX as an operating system caught on amongst the various industry system programmers because it was offered them an environment with the following standard features: 1. a simple programmers environment 2. a simple user interface 3. simple utilities or commands that can be combined to perform powerful functions 4. a permanent hierarchical file system 5. simple interface to connect the OS to devices using a consistent file format (device drivers) 6. multi-user functions 7. multi-process system functions 8. which was architecturally independent 9. All of which was permanent and transparent to the user.
1970s - Unix History & Development 1972 - Unix was re-written mostly in C, a new programming language developed by Dennis Ritchie. Being written in this high-level language greatly decreased the effort needed to port it to new machines. This made it very easy to run it as a cross platform operating system. Allowing more sites/programmers to pick it up. Unix as an OS, had truly started. 1974 - Thompson and Ritchie publish a paper in a Communications magazine describing the new Unix OS. This generated enthusiasm in the Academic community They saw its potential for a great teaching tool for their students who were starting to study programming and systems development. So AT&T gave it to the universities.
Thru the late 1970s Unix moves into the Unis 1974 - Berkeley University receives a copy of UNIX from AT&T. Many other universities also received a copy of UNIX This uptake of Unix into the universities ensured the further development & popularity of UNIX. Most universities were now using UNIX to teach their computer science students computer systems & programming. Each site had its own copy of the UNIX source code so they were able to keep developing it and were able to make modifications to the UNIX system they wanted. Whilst also sharing their code and ideas. 1977 - There are now about 500 Unix sites world-wide.
Berkeley University creates BSD 1978 - Berkeley University re-wrote most of the existing code and released their own version of UNIX called: BSD = Berkeley Software Development Berkeley has also made major enhancements to UNIX which made them a major distribution center for their new version of UNIX. They have created and added different and new utilities. The most important being a new network functionality. Called TCP/IP 1979 - A new small company called Microsoft releases its own version of unix called Xenix !
Thru the 1980s UNIX went Commercial Lots of computer companies had used the UNIX source code to develop their own proprietary versions of UNIX. Which they now sold to run on their own proprietary H/W So now, many different versions of proprietary unix existed. AT&T - System V Release 4 Berkeley University - BSD 4.4 Sun - SunOS, Solaris IBM - CPIX, AIX Honeywell - GCOS Hewlett Packard - HP/UX Digital DEC - Ultrix Compaq - VMS, Tru64 Microsoft - Xenix
Linux+ Guide to Linux Certification, 2e 13 Different Proprietary OSs are run by different vendors on their own CPU.
As many Unix variations went commercial they also went proprietary and stopped supplying the sourcecode with their version of the UNIX operating system. NOW - users could no longer view or modify the source code. This locked users into their type of H/W architecture and also gave the vendor total control over their own proprietary versions of UNIX. Software had started being copyrighted. 1980 Hobbyist started to make people take the new concept of micro-processing seriously 1981 IBM releases a new micro-processing PC running Microsoft DOS Thru the 1980s Proprietary Vendors started controlling the IT industry.
But some people didnt agree and still wanted to keep the source code open and free to all users. Richard Stallman tried to ensure this freedom. He was a systems software developer at MIT and disillusioned with the fragmentation of UNIX and the industrys turn to propriety OS systems. So he resigned and started an alternative. Richard Stallman creating the Free Software Foundation To ensure continued co-operation within the IT industry He started writing his own free OS based on UNIX. Which he called GNU = GNUs Not Unix He also developed the idea of a copyleft software license and started the GPL license.
The Free Software Foundation FSF Free Software Foundation FSF is a non profit organization designed to protect and promote: freedom for both the user and the IT industry. The term free software, refers to S/W freedom, not price. FREEDOM of Distribution NOT Free price People who put there software under the GPL believe in Free Distribution meaning that they believe that the source code for the software cannot be withheld. It does not mean that they or companies cannot charge for it.
GPL Software License Software which is placed under the GPL are designed to give people the right to . receive the source code or have the right to get it if you want it. They can charge for this service if they wish. And the new user can copy or change the existing software code to suit their needs. Or even use pieces of it, in any new GPL free programs they design. But because it originally came from a GPL software they are now obligated to place their new S/W under GPL as well and make their sourcecode available for others. Software which is put under the GPL Software License is called Opensource Software
Linux+ Guide to Linux Certification, 2e 18 Now lets discuss this diagram. Free Software Foundation AT & T
Linux+ Guide to Linux Certification, 2e 19 Today there are many Software Models Table 1-2: Software types
Linux+ Guide to Linux Certification, 2e 20 The Opensource Community This is the name given to the group of IT industry members who believe and follow the concepts of the GPL software license and opensource. Today most of the major IT companies belong to this opensource community. Companies such as: Cisco Sun IBM Compaq HP CompTIA Netscape Adobe Oracle etc etc
Linux+ Guide to Linux Certification, 2e 21 The Opensource Community Its philosophy is based on the FSF philosophy. They believe in open and distributed computing amongst the IT industry With free IT industry communication in open peer-to-peer exchanges. They believe in open & available sourcecode. They place some or all of their products under the GPL license making them opensource products. They believe in the combined development & evolution of the IT industry for all. http://www.opensource.org
1991 - Welcome to Linux Linux is a clone of UNIX. Created by Linus Torvalds who had used Unix at Uni and wanted it at home but could not afford the cost of proprietary hardware on which to run a UNIX system. The PC existed but it was commonly running the Microsoft operating systems and used the Intel chip which did not support commonly unix. DOS didnt meet his needs - Linus had developed an interest in minix. A small very basic UNIX-like system which was compatible with the Intel platform, being used in the universities for teaching. 1991 - So he created one based on minix. Linuss Pengin
The Creation of Linux Linus wrote a full complete version of a unix kernel. Which he called Linux. With the assistance of many other developers around the world. Linus believes in the opensource philosophy The Linux Kernel is written and distributed under the GPL license Its main advantage is its - Compatibility for Intel systems. This meant it could be run on generic PC computer systems. He chose a Penguin to represent his kernel Linux is part of the opensource community which believe in the open development & distribution of all sourcecode.
Linux+ Guide to Linux Certification, 2e 24 Understanding Kernel Versions Linux kernel versions are composed of: Major number Minor number If odd, referred to as a developmental kernel If even, referred to as a production kernel Revision number
Linux+ Guide to Linux Certification, 2e 25 The History of Linux is linked to UNIX Figure 1-4: Timeline of UNIX and Linux development
History of Linux 1990 Richard Stallman had nearly completed his new GNU system based on the UNIX system. He had most of the modules but was still missing the main part ! The kernel. Linus Torvalds was developing a new kernel for the Intel architecture based on the UNIX system. 1991 Linus Torvalds put the kernel he was working on out on an internet FTP server for everyone elses opinion & help. Linux was released under the GPL license. Slowly but steadily news of Linux spread and work continued. 1992 Combined with the toolkit of GNU modules & utilities, the Linux kernel had now become a fully useable operating system. Different distributions of Linux start appearing. There are now about 1000 Linux Users
Linux+ Guide to Linux Certification, 2e 27 Putting it all into Perspective
The 1990s 1993 Internet explosion starts and theres also an ISP explosion which causes the 1st viable Linux commercial application. The Apache Web Server. 1994 Mark Ewing creates a new distribution called Red Hat There are now about 500,000 Linux Users 1997 Eric Raymond writes a paper called the Catheral & Baazar in which he analyzes the development & differences of the proprietary software model verse the opensource software models. The article takes the IT industry by storm. Eric Raymond becomes the defacto front man for the new opensource movement. Netscape is the 1 st large company to go opensource. Their director reads the article and in direct response freely releases the source code of the Navigator software. There are now about 800,000 Linux Users
The 1990s 1998 Linus, Linux & the opensource movement starts becoming commonly known. And gaining momentum. Linus appears on TV and on the front of the Forbes Business Magazine. IBM, Oracle, Compaq, SAP + others announce their support for Linux. There are now about 1.5 million Linux Users 1999 1 st Linux World Conference 6000 people attend Linus delivers the opening and keynote presentation. Red Hat goes public
The 2000s 2003 Red Hat splits into 2 versions An enterprise version with which you purchase support And a Home version with no free support 2003 Novell buys SuSE Linux for $210 million Novell also buys Ximian a desktop Linux software specialist. These purchases dramatically alter the Linux landscape. IBM now the most powerful backer of Linux. To counterbalance the world of Linux they make a 50 million dollar investment in Novell. SuSE becomes the major competitor to Red Hat. Red Hat = No 1 Linux distribution SuSE = No 2 Linux distribution
Linux Today 2007 Today Linux has grown from being a hacker / home developed OS to being accepted world wide. As a commercially viable OS in the IT industry. It is highly regarded and runs many many major enterprises. Many sites are now also using it on their client machines. Linux has gone mainstream !!! Linux currently has an estimated user figures ranging from 20 to 30 million. And growing!
Linux+ Guide to Linux Certification, 2e 32 Today MOST proprietary equipment also uses Linux
Linux Distributions Remember Linus Torvalds only created the kernel Many different groups of programmers have all used this kernel and added user functionality to it then released it as a package These different packages of LINUX software' are known as distributions. There are many different distributions of Linux. Although these distributions often have their own unique flavour they are internally essentially the same due to the kernel. In most cases, they are available at no charge via FTP and in other cases they may be purchased on CD for a relatively low cost, or as a companion to a Linux book.FTPpurchasedbook
Linux+ Guide to Linux Certification, 2e 34 Table 1-4: Common Linux distributions