Objectives In this lesson, you will learn to: Define operating systems

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The Linux Operating System: An Introduction

Lesson 1A / Slide 1 of 29Introduction To Linux

ObjectivesIn this lesson, you will learn to:

• Define operating systems

• Identify the functions of an operating system

• Trace the history of the Linux operating system

• Identify the components of Linux architecture

• Log on and log out from a Linux session

• Use the date command

• Identify the current users working on the system

• Find the uptime of the system

• Open the manual pages of the system

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Operating Systems• Operating system is a software program that manages the computer hardware,

system resources, memory, and interaction between the system and its users.

• Some popular operating systems are:

• Linux

• Unix-Solaris, SCO and Irix

• Microsoft DOS

• Microsoft Windows 95

• Microsoft Windows 98

• Microsoft Windows NT Server 4.0

• Microsoft Windows 2000 Server

• Microsoft Windows Server 2003

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Functions of an Operating System• The functions of an operating system are:

• Translates a command keyed in by a user to binary code for the CPU to understand the command

• Handles requests for memory from various applications running on the system

• Handles communication between the devices and the CPU

• Rations out the CPU time enabling programs to run concurrently

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Single-User System

• A single user system is a small, general-purpose system, used by one person at a time such as a personal computer (PC).

• The example of a single-user operating system is MS DOS.

Multi-User System

• A multi-user system can run multiple programs concurrently, share multiple resources such as printers and disks, and support multiple users working simultaneously on a system.

• The examples of multi-user operating systems are:

• Linux

• Unix

• Windows NT Terminal Server

• Windows 2000 Terminal Server

• Windows 2003 Terminal Server

Types of Systems

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Types of Systems (Contd.)• A multi-user system:

• Is a computer with several terminals attached to it

• Can consist of one CPU with high processing power

• Can have multiple CPUs to process multiple applications simultaneously

• Supports multi-programming and multi-tasking

• Has higher capacity hard disk to store large amount of data

• There are two types of terminals:

• Dumb terminal

• Smart terminal

• A terminal is an interface that accepts commands from users and sends them to the server for execution.

• A server is a computer that executes the requests sent by the client computers attached to it.

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History of Unix • In 1965, Bell Labs and Massachusetts Institute of Technology (MIT) along with

General Electric developed one of the first multi-user computer systems called Multiplexed Information and Computing Service (Multics).

• Around 1969 Ken Thompson and Dennis Ritchie, two Bell Labs engineers developed Uniplexed Information and Computing Service (Unics), which was later changed to Unix.

• In 1973, Ken Thompson and Dennis Ritchie re-wrote Unix using the C programming language.

• In 1983, an MIT scientist, Richard M. Stallman, launched the GNU’s not Unix (GNU) project to create Unix-like operating system but free from licensing charges.

• To organize the work on the GNU project, Stallman and other people created the Free Software Foundation (FSF).

• FSF developed the General Public License (GPL) to build a body of free software protected from those who would use it to create proprietary closed-source systems.

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Evolution of Linux• In 1991, Linus Torvalds, a student, while working on Minix wrote the source code

for the kernel, and named it Linux.

• Torvalds made the Linux kernel available on the Internet.

• The Linux kernel was combined with the GNU system resulting in a complete operating system called GNU/Linux because it was a combination of the GNU system and Linux as the kernel.

• Linux follows the open development model which means that the current development version of Linux is always open to everybody.

• Tux, the Linux penguin, is the official mascot.

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Features and Advantages of Linux

• The features of Linux are:

• Multi-programming

• Time-sharing

• Multi-tasking

• Virtual memory

• Shared Libraries

• POSIX-Compliance

• Samba

• Network Information System (NIS)

• Cron Scheduler

• Office Suites

• Data archiving utilities

• Licensing

• Web server

• The advantages of Linux are:

• Reliability

• Backward compatibility

• Simple upgrade and installation process

• Low total cost of ownership

• Support for legacy devices

• GUI interface

• Multiple distributors

• Excellent security features

• Support for high user load

• Support for development libraries

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Linux ArchitectureComponents of Linux operating system

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Linux Architecture (Contd.)• The kernel:

• Is the core of Linux operating system program

• Controls the resources of the computer

• Interacts directly with the hardware

• The shell:

• Is a user interface providing services that a user wants

• Protects the user from knowing the intricate hardware details

• Linux utilities and application programs:

• Are a collection of programs that service day-to-day processing requirements

• Are invoked through the shell

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Comparing Linux with Unix

• Linux was developed keeping Unix as a reference model and continue to have the same basic architecture and features.

• Linux and Unix operating systems differ in:

• Hard disk space requirement

• Availability of shells

• Distributions or variants

• Licensing

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Distributors of Linux• All the distributors use the Linux kernel.

• The distributors add their own utilities and applications and sell these as a customized package.

• The following are the popular distributors of Linux:

• Red Hat and its variations, such as Linux ES, Linux AS, Linux WS, Desktop, and Fedora Core

• Mandrake

• Debian

• SuSE

• Slackware

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Starting a Linux Session• After you boot the Linux system, the following prompt appears:

Fedora Core release 2 (Tettnang)

Kernel 2.6.5-1.358 on an i686

linuxpc1 login: _

• At the login prompt, you can enter your login name and password: linuxpc1 login: tom

Password: [user enters password here]

• After successful login, you will see the following prompt on the screen:[tom@linuxpc1 tom]$ _

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Connecting to the Linux Server Remotely

• You can connect to a Linux server from any computer that has operating systems, such as Windows 9x and Windows NT or 2000, using the following utilities:

• Telnet: You can launch Telnet from the command line by typing the following command:

telnet 172.17.55.242

• PuTTY: Is a third-party program.

• Allows you to make ssh (Secure SHell) connections from the computer that has Windows operating system

• Runs as an executable application that does not need to be installed on your computer

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Security for the Linux User: Passwords• Linux ensures that only authorized users can access the system.

• Linux allows you to have a password associated with your login name as an additional measure of security.

• The Linux prompt appears only if you have entered both the user name and the password correctly, otherwise you are asked to re-enter the user name followed by the password.

• Passwords are not displayed on the screen while they are being entered.

• A user can change the password using the passwd command.

• The syntax to use the passwd command is:[steve@linuxpc1 steve]$ passwd

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Viewing the System Date and Time

• Users can display the current date and time using the date command. [steve@linuxpc1 steve]$ date

Thu Aug 12 15:56:21 IST 2004

[steve@linuxpc1 steve]$ _

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Modifying the Screen• Linux allows you some measure of screen manipulation with the clear and

tput commands.

• The clear command: Clears the terminal screen.[steve@linuxpc1 steve]$ clear

• The tput clear command: Clears the standard output device, the screen, and positions the cursor at the top left corner of the screen.

[steve@linuxpc1 steve]$ tput clear

• The tput cup command: Positions the cursor at the specified row and column.

• The tput smso command: Sets the screen to reverse video.

• The tput rmso command: Sets the screen back to normal.

• The tput blink command: Displays a blinking output.

• The tput reset command: Resets the screen to the default settings.

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Identifying the Current Users Working on a System

• The who command is used to display the names of all the users who are currently logged in.

[steve@linuxpc1 steve]$ who

root tty1 Sep 21 12:29

root tty2 Sep 21 14:54

andrew pts/0 Sep 21 11:36 (172.17.55.178)

tom pts/1 Sep 21 11:15 (172.17.55.133)

• The ‘who am i’ command displays the name of the current user logged in.[steve@linuxpc1 steve]$ who am I

steve pts/0 Sep 22 18:08 (172.17.55.167)

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Determining the Uptime of the System

• The uptime command is used to find the duration for which the system has been running.

• It gives a one‑line display of the current time, how long the system has been running, how many users are currently logged on, and the system load averages for the percentage CPU utilization in the last 1, 5, and 15 minutes respectively.

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Displaying the Manual Pages

• Linux provides two commands for displaying reference on commands:• man: Displays pages of the specified command from the Linux

reference manual. For example, to get detailed information about the ls command, you can use the following command:

[steve@linuxpc1 steve]$ man ls

• info: Provides detailed information about a command. The syntax to use the info command is:

$ info [options] [menu item]

For example, you can use the following command to display detailed information about the emacs editor:

$ info emacs

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Ending a Linux Session

• Typing exit or logout at the shell prompt ends your current Linux session.

• The system then displays the login: prompt on the screen to initiate another login session in Linux.

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Demonstration-Initiating a Linux Session

• Problem Statement

• Deez Telecommunications Inc. is a call center operating in three shifts per day. Tom is the system administrator with Deez Telecommunications for the morning shift. He needs to perform the following routine tasks:

• Report the daily attendance of each shift

• Check the load on the Linux server through the shift

• Change the password, once every week, for security reasons

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Demonstration-Initiating a Linux Session (Contd.)

• Problem Statement (Contd.)

• Tom submits a report to the management, on all the above issues, by the end of the shift. Today, Tom has received several complaints about the server being slow. The users are facing difficulty accessing and working on the server over the network. Help Tom to identify the load average in the system and submit the same in his daily report.

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Demonstration-Initiating a Linux Session (Contd.)

• Solution

• To identify the clogging in the network and to prepare the daily report, Tom needs to perform the following tasks: 1. Connect to the Linux server remotely.2. Identify the number of users logged on to the Linux server

and their login time.3. Identify the percentage CPU utilization of the system.4. Change the password as it is the sixth day today. 5. Consolidate and submit the report.

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SummaryIn this lesson, you learned:

• Software is categorized into:

• System software

• Application software

• The functions of an operating system include:

• Command interpretation

• Memory management

• Peripheral management

• Process management

• Operating systems can be classified as:

• Single-user operating systems

• Multi-user operating systems

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Summary (Contd.)• A multi-user system consists of a central server connected to several

terminals that could be either:

• Dumb terminals

• Smart terminals

• UNIX was the first multi-user operating system.

• Linux follows the open development model.

• Linux has the following features:

• Multi-programming

• Time-sharing

• Multi-tasking

• Virtual memory

• Shared libraries

• POSIX compliance

• Samba

• Network Information Service (NIS)

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Summary (Contd.)• CRON scheduler

• Office suites

• Various data archiving utilities

• Licensing

• Linux has the following advantages:

• Reliability

• Backward compatibility

• Simple upgrade and installation process

• Low TCO

• Support for legacy devices

• GUI through the X Window system

• Multiple Distributions

• No known viruses

• Excellent security features

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Summary (Contd.)• Can support a high user load

• Has a number of development libraries

• You can start a Linux session by logging on to the Linux server or by connecting to the Linux server remotely.

• You can log out from a Linux session with the logout or exit command.

• You can remotely log on to a Linux server using the following utilities:

• Telnet

• PuTTY

• Security for a Linux user is offered in the form of a unique username and password that is known to the user only.

• Some other commonly used commands are:• date: Used to view and change the current system date and time• tput clear: Clears the contents of the screen• tput cup: Used to position the cursor on a specified row and column

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Summary (Contd.)• tput smso: Sets the screen to reverse video• tput rmso: Sets the screen back to normal• tput blink: Used for a blinking output• tput reset: Resets the screen back to the default settings• who: Displays the information of all the users currently logged on the

Linux system• uptime: Finds the duration for which the system has been running• man: Displays help on any Linux command• info: Displays detailed help on any Linux command in form of

hyperlinks

Documents

Objectives In this lesson, you will learn to: Define operating systems