1. Objectives In 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
Introduction To Linux

2. 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
Introduction To Linux

3. 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
Introduction To Linux

4. Types of Systems 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
Introduction To Linux

5. 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.
Introduction To Linux

6. 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.
Introduction To Linux

7. 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.
Introduction To Linux

8. 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
Introduction To Linux

9. Linux Architecture Components of Linux operating system
Introduction To Linux

10. 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
Introduction To Linux

11. 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
Introduction To Linux

12. 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
Introduction To Linux

13. Starting a Linux Session
After you boot the Linux system, the following prompt appears:
Fedora Core release 2 (Tettnang)
Kernel 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]$ _
Introduction To Linux

14. 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
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
Introduction To Linux

15. 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]$ passwd
Introduction To Linux

16. Viewing the System Date and Time
Users can display the current date and time using the date command.
steve]$ date
Thu Aug 12 15:56:21 IST 2004
steve]$ _
Introduction To Linux

17. 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]$ 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]$ 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.
Introduction To Linux

18. 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]$ who
root tty1 Sep 21 12:29
root tty2 Sep 21 14:54
andrew pts/0 Sep 21 11:36 ( )
tom pts/1 Sep 21 11:15 ( )
The ‘who am i’ command displays the name of the current user logged in.
steve]$ who am I
steve pts/0 Sep 22 18:08 ( )
Introduction To Linux

19. 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.
Introduction To Linux

20. 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]$ 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
Introduction To Linux

21. 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.
Introduction To Linux

22. 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
Introduction To Linux

23. 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.
Introduction To Linux

24. 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:
Connect to the Linux server remotely.
Identify the number of users logged on to the Linux server and their login time.
Identify the percentage CPU utilization of the system.
Change the password as it is the sixth day today.
Consolidate and submit the report.
Introduction To Linux

25. Summary In 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
Introduction To Linux

26. 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)
Introduction To Linux

27. 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
Introduction To Linux

28. 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
Introduction To Linux

29. 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
Introduction To Linux