Introduction To Linux Operating System

Introduction to the Linux Operating System

©NIIT Linux/Lesson 1/Slide 1 of 32

Objectives

In this lesson, you will learn to:

Identify the functions of an operating system

Differentiate between single-user and multi-user operating systems

Identify the inception, growth, features, and architecture of Linux

Identify the various shells available in Linux

Start a Linux session

List the users who are currently logged in



Objectives(contd.)

Assign passwords to a Linux user using the passwd command

End a Linux session

Identify the features of the Linux filesystem

Create a directory using the mkdir command

Delete a directory using the rmdir command

List the contents of a directory using the ls command

Copy a file using the cp command



Objectives(contd.)

Move a file using the mv command

Delete a file using the rm command

Use man command to get online help



Getting Started

Operating Systems

An operating system (OS) is a software program that acts as an interface between a user and a computer, e.g Linux, Unix, Microsoft DOS etc

Functions of an Operating System

Command Interpretation

Process Management

Memory Management

I/O Operations and Peripheral Management

File management



Getting Started(contd.)

Types Of Systems

Single-User Systems

A single-user system was designed for use by one person at a time. A personal computer (PC) is a popular single-user system

Single–User Operating Systems

MS DOS (Disk Operating System) is an example of a single-user operating system




Types Of Systems(contd.)

Multi-User Systems

More than one user can work simultaneously on a multi-user system

Printer Communication Lines

System Unit -Processor -Disk(s) -Tape(s) -Floppy Disk(s)

System ConsoleGraphical or text

TerminalsRemote User

Terminals

Multi-user System




Types Of Systems(contd.)

Multi–User Operating Systems

Linux, Unix, and Windows NT Terminal Server are examples of multi-user operating systems

More than one user can connect to the system and work concurrently at any point in time



Flavours of Linux

Distributor Name Website

Red Hat http://www.redhat.com

Caldera http://www.caldera.com

Mandrake http://www.linux-mandrake.com

Debian http://www.debian.org

SuSE http://www.suse.com

Slackware http://www.slackware.com



The Linux Architecture

The Linux operating system consists of the following:

Kernel

Shell

Utilities and Application Programs



Shells Available in Linux

Bourne Shell (sh)

C Shell (csh)

Korn Shell (ksh)

Restricted Shell (rsh)

Bash Shell (bash)

Tcsh Shell (tcsh)

A Shell (ash)

Z Shell (zsh)



Starting a Linux Session: Logging on

Connect to a computer running the Linux operating system from any other computer using the telnet program

telnet <hostname or IP address>

The administrator assigns each user a HOME directory when a new logon account is created. When you log on, you are taken directly to your HOME directory



Listing the Users Currently Logged In

A list of users who are currently logged in can be found by using the who command

who [options]



Security for the Users: Passwords

Linux provides an additional measure of security by allowing you to have a password associated with your login name

The combination of the login name and password is checked by Linux to verify if it is an authorized user

Changing the User Password

Passwords can be changed using the passwd command

The passwd command asks for the old password to ensure that only the authorized user is trying to change the password



Root user:

The root user (also known as the superuser) is the administrator of the Linux operating system

Ending a Linux Session: Logging out

Typing exit or logout at the command prompt ends your current Linux session. You can also press <CTRL>+d to end the Linux session



The Linux Filesystem

Defaul t

Star t

/

bin boot home etc dev

tom michael user3

Desktop Templates program1

program2

cat cp chmod

ls

usr

Legend

File

Directory



The Linux Filesystem (contd.)

The /bin directory stores many utilities of Linux

The /dev directory stores all the device-related files for the system

The /etc directory stores the operating system-related data which users and the operating system need to refer to, such as the passwd file

The /lib directory contains libraries of data for the compilers installed in the Linux operating system, for example, the C language routines

The /home directory generally contains all the HOME directories of users



The Linux Filesystem (contd.) The /usr directory stores the operating system files

that are not involved in the boot process

The /var directory has information specific to different utilities of Linux



In Linux, File Names: Can be up to 256 characters long

Can contain special characters, except for ‘/’

Can contain both uppercase and lowercase letters of alphabets

Are case-sensitive

Should not have a blank or a tab



Types of Files in Linux

Character Device files

File Types

Block Device files

Hard links Symbolic links

Ordinary files Directory files Special files



Types of Users in Linux

System Administrator

A System Administrator (SA) is primarily responsible for the smooth operation of the Linux operating system

File Owner

The user who creates a file is said to be its owner

Group Owner A group of users is also given a name, just as a

user is given a name

Other Users

These are users who do not belong to a particular group



Directory Commands in Linux

Identifying the Current Directory Path

The pwd (print working directory) command is used to display the full path name of the current directory

Changing the Current Directory

The cd (change directory) command changes the current directory to the directory specified

Creating a Directory

The mkdir (make directory) command is used to create directories



Directory Commands in Linux (contd.)

Removing a Directory

The rmdir (remove directory) command removes the directory specified

Listing the Contents of a Directory

The ls command is used to display the names of the files and sub-directories in a directory



File Commands in Linux

The cat (concatenate) command displays the contents of the specified file

Copying Files

The cp (copy) command duplicates the contents of the source file into a target file

cp [options] <source file/s> <destination directory/file>

Removing Files

The rm (remove) command is used to delete files or directories

rm [options] file/s



File Commands in Linux (contd.)

Moving and Renaming Files

The mv (move) command is used to move a file or directory from one location to another or to change its name

mv [option] source destination

Displaying the Contents Page–Wise The more command is used to display data one

screen-full at a time. While viewing a file using the more command, once you have scrolled down, you cannot move up

more [options] <filename>




Displaying the Contents Page–Wise (contd.)

The less command is similar to the more command except that you can scroll upwards also while viewing the contents of a file

less [options] <filename>

Wildcard Characters

The shell offers the facility to perform an operation on a set of files by the use of certain special characters in the command in place of the actual file names




Wildcard Characters (contd.)

The * Wildcard

The * wildcard is interpreted as a string of none, one, or more characters

The ? Wildcard

The ? wildcard matches exactly one occurrence of any character

The [ ] Wildcard

The [ ] wildcard can be used to restrict the characters to be matched



Getting Online Help

The man command is used to get online help to a user about the various options for any command in Linux

man <command name>



Summary

In this lesson you learned that: An operating system has the following functions:

Command Interpretation

Process Management

Memory Management

I/O Operations and Peripheral Management

File Management

A single-user system is designed for use by one person at a time

More than one user can work simultaneously on a multi-user system



Summary(contd.) The Linux operating system consists of kernel, shell,

utilities, and application programs

Some of the commonly available shells in Linux along with their executable file names are:

The Bourne shell (sh)

the C shell (csh)

The Korn shell (ksh)

The Restricted shell (rsh)

The Bash shell (bash)

The Tcsh shell (csh/tcsh)



Summary(contd.) The A shell (ash)

The Z shell (zsh)

The telnet command is used to connect to a Linux server

The passwd command is used to change the password of the user

For organizing data on the disk, Linux provides a filesystem which allows you to group files in a convenient manner. The Linux filesystem has a hierarchical structure and files can be stored under directories



Summary(contd.)

In Linux, there are three categories of files: Ordinary files

Directory files

Special files

The types of users in Linux are: System Administrator

File owner

Group owner

Other users



Summary(contd.)

In Linux, chat and e-mail programs are used to communicate with each other.

Documents

Introduction To Linux Operating System