Fundamentals of Linux Final

Fundamentals of Linux Final

Linux Computing Environment

1

Objectives

Upon completion of this module, you should be able to:

 List the four main components of a computer

 Describe the three main components of the Linux

operating system

 Identify the three most common shells in the Linux system

 Distinguish between the multitasking, multiuser, and

distributed

processing capabilities of the Linux system

Discussion – Several different components work together to make up

a computer system and a networked environment What are some of these components?

Introduction to Linux

The UNIX operating system was originally developed at AT&T BellLabs in 1969 It was created as a tool set by programmers forprogrammers The early source code was made available touniversities all over the country Programmers at the University

of California at Berkeley made significant modifications to theoriginal source code and called it BSD (Berkeley SoftwareDistribution) UNIX

They sent this new version of the UNIX environment to otherprogrammers around the country, who then added tools andcode as they saw fit Possibly the most important advance made

to the software by the programmers at Berkeley was the addition

of networking software which allowed the operating system tofunction in a local area network (LAN)

Linux is a UNIX-like operting system, developed by LinusTorvalds, a student at Helsinki University in Finland, in 1991 It is

a modern, flexible, mature and free operating system Although

it started life on the Intel platform, it has since been ported tomany other platforms such as Amiga, DEC Alpha, Apple Power

PC, Sun workstations, and others Linux boasts many otherfeatures:

 Multitasking Linux is a true preemptive multitasking

operating system All processes run independently of each other and leave processor management to the kernel

 Symmetrical multiprocessing Linux currently scales up to

 Advanced memory management Traditional UNIX

systems use swapping to manage memory, where the entire memory structure of a program is written to disk when the system is running low on memory Linux uses paging, a

method that intelligently allocates memory when system memory is running low by prioritizing memory tasks

 POSIX support POSIX defines a minimum interface for

UNIX-type operating systems Linux currently supports POSIX 1003.1 This ensures that POSIX-compliant UNIX programs will port easily to Linux

 Multiple file systems Linux supports several different file

system formats, including DOS/Windows, OS/2, and Novell formats This makes interoperability a reality between

operating systems

Main Components of a Computer

The four main components of a computer are the random access

memory (RAM), the central processing unit (CPU), the input/ output (I/O), and the hard disk or other mass storage device.

Figure 1-1 Main Components of a Computer

Random Access Memory (RAM)

Random access memory, located on the memory board, is the main

computer memory, often referred to as primary memory

Primary memory is that part of memory where the activity

of the running system takes place When you hear, “My system has 16 Mbytes of memory,” the speaker is talking about primary memory or RAM

A software program resides on the hard disk When it is

activated, an image or copy of that program is loaded into RAM

Images in RAM remain as long as they are needed Once these images are no longer required, they are overwritten

by other images If power is lost or the system is rebooted, images in RAM disappear

Central Processing Unit (CPU)

The central processing unit is the computer logic chip that executes instructions (processes) received from the

primary computer memory(RAM) These instructions are stored in binary language

Hard Disk (or Other Forms of Mass Storage)

The hard disk is a magnetic storage device where information is stored All files, including applications (utilities), are stored on a hard disk

The Linux Distributed Computing Solution

The Linux computing environment is based on the UNIX

operating system Versions of the UNIX operating system run on many different computer systems – microcomputers, personal computers (PCs), and mainframes

The operating system is a set of programs that manages all computer operations It also provides a link between the user and system resources, converting requests which come from the mouse and/or keyboard into computer operations

There are three main parts of the operating system:

 Kernel

 Shell

 File system

Kernel

The kernel is the core of the Linux computing environment It

performs the following functions:

 The kernel is an executable file that gets loaded into memory when your system boots It is called /kernel/genunix

 Manages devices, memory, and processes

 Controls the functions (transmission of information)

between the system programs (utilities) and the system hardware

 Manages functions such as:

o Swap space – A reserved part of the disk for the

kernel to useduring processing

o Daemons – Processes that perform particular system

tasks andmonitor disks and execution

o File systems – A hierarchy of directories,

subdirectories, and files

Shell

A shell is an interface between the user and the kernel It acts as

an interpreter or translator In other words, the shell accepts commands issued by you, interprets these commands, and

executes the appropriate programs Three shells are available inthe Linux environment:

 Bourne shell ($) – The default shell for the Linux computing

environment The Bourne shell was developed for the AT&T

System V.2 UNIX environment This shell does not have aliasing or history capabilities It is typically used by

system administrators

 Korn shell ($) – A superset of the Bourne shell It has many

of the Bourne shell features plus added features such as aliasing and history This is the industry standard for

normal system users

 C shell (%) – A shell based on the C programming

The File System

The Linux computing environment file structure is a hierarchy of directories, subdirectories, and files that are grouped together for a specific purpose

 Directory – A location for other files and directories The

Linux file system, or directory structure, enables you to

create files and directories accessed through a hierarchy ofdirectories

 Subdirectory – Any directory below another directory For

example, some of the subdirectories under the root (/) directory are/usr, /etc, and /kernel

root ( / )

usr opt dev etc home var bin sbin lib user1 user2 user3

Figure 1-4 Common Linux Subdirectories

The file system is integrated with the kernel to provide an

organizational structure to store your data

The topmost directory is called the root directory It is the

starting point of the file-system hierarchy The root directory (/)

is required for the operating system to function and contains critical systems files (such as the kernel, called

The /etc directory contains system administration files

The /home directory contains the user’s home directory

Depending on how the system has been set up by the

administrator, the home directories may instead be found in /export/home

The /dev directory contains files which are pointers to device names.

The file system organizes data in a hierarchical structure of directories,

similar to the way a filing cabinet stores information

Directories are like file drawers Subdirectories are similar to folders Files are like the individual pages of information

contained in the folder

The Linux operating system contains many different kinds of files:

Main Capabilities of the Operating System

The Linux computing environment was designed for:

 Multitasking – Enables the kernel to keep track of several processes simultaneously, which allows more than one tool

or application to be used at a time

 A user can run a program (like a spreadsheet) and edit a document using a word processor at the same time.

 Multiuser capability – Enables more than one user to

access the same system resources

 Distributed processing – Enables the use of resources acrossthe network

Main Capabilities of the Common Desktop Environment (CDE)

CDE is Motif-based and users of other UNIX and personal

computer (PC) desktops should be comfortable using CDE; many

of the features are common to other desktop environments

The Common Desktop Environment (CDE)

 Is a graphical user interface (GUI) between the user and the operating system

 Provides built-in menus for users to select and run utilities and programs without using Linux environment commands

 Enables users to control multiple documents or

applications on the screen at the same time

 Controls activities in windows using both the mouse and the Keyboard

 The icons pictured above represent some of the major programs and tools

available with CDE CDE is discussed in greater detail in subsequent modules.

Exercise: Using the Linux Computing

Environment

Exercise objective – This exercise helps you review the basics of the

computing environment

Tasks

Answer the following questions:

1 Identify the four main components of a computer

 The _ manages and allocates resources among users

 The _ provides command interpretation

 The _ organizes and stores data in a hierarchical

structure

 The _ performs memory management

 The _ components are files and directories

 The _ controls disks, tapes, printers, terminals,

communication lines, and other devices

4 In the blank spaces, write one of these three capabilities:

multitasking, multiuser, or distributed processing.

 The _ capability enables users to share system

Exercise Summary

Discussion – Take a few minutes to discuss what experiences, issues,

or discoveries you had during the lab exercises

 Manage the discussion here based on the time allowed for this module, which was given in the “About This Course” module If you find you do not have time to spend on discussion, then just highlight the key concepts students should have learned from the lab exercise.

1 Identify the four main components of a computer

Memory, CPU, I/O, and hard disk

2 Describe the three main functions of the kernel

It manages all computer operations, controls the hardware, and

 The kernel manages and allocates resources among users.

 The shell provides command interpretation.

 The file system organizes and stores data in a hierarchical

structure

 The kernel performs memory management.

 The file system components are files and directories.

 The kernel controls disks, tapes, printers, terminals,

communication lines, and other devices

4 In the blank spaces, write one of these three capabilities:

multitasking, multiuser, or distributed processing.

 The multiuser capability enables users to share system

resources

 The multitasking capability is the ability to perform several

processes simultaneously

 The distributed processing capability is the ability to use

resources across a network

Check Your Progress

Before continuing on to the next module, check that you are able to accomplish or answer the following:

 List the four main components of a computer

 Describe the three main components of the Linux operating system

 Identify the three most common shells in the Linux system

 Distinguish between the multitasking, multiuser, and distributed processing capabilities of the Linux system

Think Beyond

What features of the Linux UNIX environment set it apart from a typicalstandalone PC environment? What would some of the benefits of these features be to a company?

Accessing Your System

2

Objectives

Upon completion of this module, you should be able to :

 List the characteristics of an effective password

 Change your password

 Describe the function of a mouse button

 Log in and log out of a system from the command line

 Log in and out of a CDE session

 Manipulate windows within the CDE

 Invoke and use menus and menu bars

Discussion – Passwords are a major key to a secure system What

characteristics would a good password have?

User Accounts

You must have a user account on the system to log in The user

account is defined in the /etc/passwd file and contains the elements which identify each unique user to the system

System administrators are responsible for creating and

maintaining user accounts

The Root Account

The root account is the system administration account and is set

up by the installation process The root login account owns allsystem files and has access to all files

The /etc/passwd Entry

Each entry in the /etc/passwd file is made up of seven fields separated by a colon

 Login ID – Is the identification required by the operating system

for a successful login It is the user’s “public name.” Depending

on the system administrator, login IDs are usually somecombination of a user’s first and last names For example, userBob Wood’s login ID might be bobw, bwood, woodb, or bw2

The login ID must:

 Be limited to 32 characters

 Do not accept special characters: !, @, #, $, %,^, &

 Be unique

 Placeholder – Maintains the field for the password, which is kept

in the /etc/shadow file The /etc/shadow file containsencrypted passwords and password aging information (forexample, how long before a user must change a password andhow long a password must be in use before it can be changed).This file can only be read by the system administrator

 UID – Identifies the user to the operating system.

 GID – Identifies the primary group to which the user belongs.

 Comment – Is usually the full name of the user.

 Login directory – Is commonly referred to as the “home”

directory, where users store their files

 Default shell – Defines which shell the user will have upon login.

 Should differ from the previous password by at least threecharacters

 May contain spaces

 These password requirements do not apply to the systemadministrator (superuser)

The Mouse Buttons

The mouse settings can be modified to suit a user’s preferences Once

a setting has been modified, that setting can be stored into auserspecific file This means that any personalized settings will be thedefault whenever a CDE session is initiated

The Left Mouse Button

Most actions use the left mouse button, alternatively known asbutton 1 or the SELECT button This button is used to makeselections in any of the following ways:

 Make a window active by clicking the left mouse buttonwhile the mouse pointer is in that window area

 Invoke a window menu by clicking on the left mouse buttonwhile the mouse pointer is on the window’s menu box area

 Select an option from the Front Panel

 Select a File or Folder icon while working with the FileManager

 Open an icon by double-clicking the left mouse buttonwhile the pointer is over the icon

 Highlight text to be selected by dragging over the textarea, while the left mouse button is being pressed

The Middle Mouse Button

Button 2, also known as the ADJUST button, is used to pasteselected text The text must have been selected using the leftmouse button as described previously

The Right Mouse Button

When the right mouse button, or MENU button, is clicked or helddown, a menu of choices will appear The options available onthe menu will be determined by the position of the mousepointer when button 3 was pressed

Note – For the purposes of this course, you will be instructed to

Logging in text mode

To log in at the command line, follow these steps:

1 Type your user name (login ID) at the prompt and pressReturn

2 Type your password at the password prompt and pressReturn

Note – Your password does not appear as you type it By default,

if you do not have a password, you are automatically promptedfor one during the initial login

Logging in graphic mode

The CDE login screen replaces the usual login prompt You mustenter your login name into the appropriate boxed area, thenpress the Return key or left click on the OK button If you log inincorrectly, you must repeat the procedure of entering

your login name and password

Note – If you make a mistake when entering either your login

name or your password, you will be required to reenter bothpieces of information

Changing Your Password

Changing your password frequently helps prevent unauthorized access

to your system

To change your password:

1 If you are in text mode, goto next step If you are logged into aCDE session, right click on the background to bring up theWorkspace Manager, click on Programs, and open a terminalwindow (On some systems, the Workspace Manager will have amenu selection labelled Windows If that is the case, click on thisinstead of Programs to access a terminal window.)

2 Type the passwd command after the system prompt and pressReturn

3 When the prompt Enter login password: appears, type yourcurrent password and press Return

4 When the prompt New password appears, type your newpassword and press Return

5 When prompted, retype the new password and press Return.(This is required for verification of the new password by thesystem.)

Example

$ passwd

passwd: Changing password for user2

Enter login password:

New password:

Re-enter new passwd:

$

 If the users are unable to change their passwords due to cred table errors, use

the following command on the Network Information Service Plus (NIS+) server:

newkey -u username -s nisplus

This puts the user login password in the NIS+ cred table.

Exercise: Accessing Your System

Exercise objective – In this exercise, you will practice logging in on

the command line, changing your password, logging out, and other basic CDE skills

Tasks

Complete the following steps:

1 Obtain a user name and password from your instructor

2 Log in to the system

3 Change the password to mypass1

4 Log out of the system

5 Log back in to the system with the new password, then log back out

6 At the CDE login screen, enter the following (incorrect) details:

Login Name: nosuchuser

Password: wrong

Observe the information displayed on the screen

7 At the CDE login screen, enter your own (correct) details and log in

to a CDE session

8 Using the correct mouse and Front Panel buttons, switch from the default workspace display to Workspace Three From Workspace

Three, switch back to Workspace One

9 Click on the Text Note icon on the Front Panel to open a Text Note window

10 Once the Text Note window has been opened, convert the window

to an icon

11 Convert the Text Note icon back to a Text Note window

12 Move the Text Note window to another position on your workspace display

13 Make the Text Note window take up all of your workspace display area

14 Reduce the Text Note window back to its previous size

15 Type some text into the Text Note window, then attempt to close the window

16 Confirm that you want to close the window without saving the text

17 Exit from your current CDE session

18 Confirm that you want to log out

19 Once you are back at the CDE Login Screen, log in again using yourallocated login name and password.

Exercise Summary

Discussion – Take a few minutes to discuss what experiences, issues,

or discoveries you had during the lab exercises

 Manage the discussion here based on the time allowed for this module, which was given in the “About This Course” module If you find you do not have time to spend on discussion, then just highlight the key concepts students should have learned from the lab exercise.

3 Change the password to mypass1.

$ passwd

old password:

new password:

re-enter new password:

4 Log out of the system

$exit

Check Your Progress

Before continuing on to the next module, check that you are able toaccomplish or answer the following:

 List the characteristics of an effective password

 Change your password

 Describe the function of a mouse button

 Log in and log out of a system from the command line

 Log in and out of a CDE session

 Manipulate windows within the CDE

 Invoke and use menus and menu bars

Think Beyond

On a UNIX system, it is not unusual for users to be forced to changetheir passwords on a regular basis What are some reasons for this?

Common Desktop Environment - KDE

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