MODULE 4

“Hello everbody out there using minix – I am doing a (free) operating system just a hobby, won’t be big and professional like gnu) for 386(486) AT clones”

What is Linux?

In 1991, Linus Torvals – 21 years old student.

University of Helsinki, Finland. Developing Linux Kernel as a hobby. He wishes to improve upon the design

of Minix, an educational operating system.

Minix source code serves as the starting point for Torvalds’s Linux project.

In Sept 1991, 1st version of Linux Operating System release

What is Linux?

Linux is a most popular, free open-source operating system.

Free distributed, full featured OS. Available to the public for

examination and modification. Developed based on Unix

What is Linux?

Linux was originally created by Linus Torvalds with the assistance of developers from around the globe.

Linux is free to download and install, edit and distribute.

Linux is a very powerful operating system

Popular throughout the world.

What is Linux?

User of the OS benefits from a community of developers actively debugging & improving the kernel.

Absent of licensing fees and restrictions – ability to completely customize the OS to meet specific needs.

Linux is not centrally produced by a corporation, Linux users can receive technical support for fee from Linux vendors or for free though a community of users.

What is Linux?

Runs on multiple hardware platforms From the smallest to the largest, and

serves a wide variety of needs from servers to movie-making to running businesses to user desktops.

Because of its speed, stability and low cost, Linux became the fastest growing operating system for servers (the computers than run big companies, the Internet, large networks, etc.).

What is Linux?

For all the same reasons Linux has become so popular on servers, to desktop computers.

There are versions of Linux (called distributions) created specifically for desktop use, such as Linspire and Freespire, which give you the stability of Linux, but with the ease of a Windows environment.

Linux Distributions

also known as the GNU/Linux distribution

a family member of the Unix-like software distributions

Linux kernel lies as the basis of these distributions.

Linux distributions are available in different forms because most of the kernels and supporting packages used are combination of open source and free software.

Linux Distribution

This is the reason why they are widely used in embedded systems and for things like booting from a floppy disk

Linux Distribution

Linus Torvalds created Linux and distributed early versions across the Internet for the enjoyment of many hardcore hackers

•Today, Linux is distributed in many ways, including CD-ROMs, tapes, Internet and even inside diskettes

•A Linux distribution has the utilities and other programs in Unix

List of Linux Distribution RedHat –The most popular Linux. Evolving

fast with great GUI’s and other auto-detect facilities and tools. Latest version : RedHat 9.0

Slackware –The first Linux distribution created. Inherited from the real Linux from Linus Torvalds. Quite tedious to master but good for research purposes.urce software

Mandrake –Competitors to RedHat. Has good GUI’s and good for servers. Easy to master and has many online help.

List of Linux Distribution Lindows –It has most Linux and Windows

capabilities. Evolving fast to compete Microsoft Windows. The good news is : it is FREE

UnitedLinux –A combination of Slackware, SuSE and Caldera. Competitor for RedHat and big threat for Windows.

Other distributions such as : SuSE, Caldera, Debian, OpenLinux, FreeBSD, etc.

Linux OS

“Linux” refers to the kernel, the core of the OS

The kernel is what actually makes the computer run

Developed under the GNU General Public License

GNU General Public License Sponsored by the Free Software

Foundation A method for a program author to

provide the code yet protect it from becoming proprietary

Any program developed under this license can be changed at will

However, no money can be charged for the code itself, it must be freely available

Can charge for support, development and distribution costs

GNU and Linux tools

GNU stands for “GNU’s Not Unix” Richard Stallman created the

foundation to help write free versions of the Unix software tools

Linux benefits from most of these tools, which is why often you’ll see GNU/Linux

Linux OS

Multitasking OS Every application has their own memory

space The kernel keeps track of everything

Multiuser One computer can serve the needs of

many users at once Each user can have different settings for

the same application Standard Unix/Linux concept

Linux OS

Programmable shells Linux is the most flexible OS available

where programmers can write their own programs inside Linux shells

Device independence under Linux Linux is device independence as well as

Unix Programmers all around the world

developed drivers of many hardware for Linux

Windows Interface

Since no one company controls everything, there are numerous desktop environments

Each is just as interface to the X window system tools

The two most popular are KDE and GNOME

Most window managers have features like multiple desktops per user

Linux Commands - ls

The ls command is used to list the contents of a directory. It is probably the most commonly used Linux command. It can be used in a number of different ways. Here are some examples:

ls –list the files in the working directory ls /bin –list the files in the /bin directory (or any

other directory you want to specify) ls –l –list the files in the working directory in long

format ls –l /etc /bin –list the files in the /bin directory

and the /etc directory in long format ls –la list all files (even ones with names

beginning with a period character, which are normally hidden) in the parent of the working directory in long format

Linux Command - cp

The cp program copies files and directories. Examples:

cp file1 file2 –copy a single file cp file1 file2 file3 directory –copy

multiple files to a different directory

Linux Command - MV

The mv command performs two different functions depending on how it is used. It will either move one or more files to a different directory, or it will rename a file or directory.

Examples: mv file1 file2–rename a file mv file1 file2 file3 directory–move

files to a different directory

Linux Command - chmod

The chmod Command We use the chmod command to

change the access mode of a file. This command comes in many flavors, but we'll be talking primarily about one of them.

chmod who=permissions filename This gives “who” the specified permissions for a given filename.

Linux Commands

rm The rmcommand deletes (removes) files.

Example: rm filename

rmdir The rmdircommand deletes directories. Example: rmdir directory name

mkdir The mkdircommand is used to create directories.

Example: mkdir directory name

Linux Commands

man Online help for each of the various Linux

commands Linux will display any information you type Example: man ls –it will show description of ls

command

more Display a screenful of a text file You can look through a text file without

invoking an editor, printing the file, or trying to pause the terminal as it displays the file

Linux System Administrator Every aspect of the system can fall within

the realm of a system administrator Entire books have been written about just

the software side, and for most system administrators, hardware, networks, and even programming fall into their laps

Almost every user, and many administrators, never see what is happening as the system is booting

Linux System Administrator Those who do, often are not sure what is

happening. From the time you flip the power switch to

the time you get that first login prompt, dozens of things must happen, many of which happen long before the system knows that it’s running Linux

Knowing what is happening as the system boots and in what order it is happening is very useful when your system does not start the way it should

User Accounts

Users gain access to the system only after the system administrator has created user accounts for them

These accounts are more than just a user name and password;

they also define the environment the user works under, including the level of access he/she has

User Accounts (cont)

Users are added to Linux systems in one or two ways.

You could create the necessary entries in the appropriate file, create the directories, and copy the start-up files manually

Or, you could use the addusercommand, which does that for you

Basic Linux Administration – Linux User Root

Controls all system files Only user that can do “anything”, even look

at/delete another users’ files Usually the only user that can install most

programs Normal users

Each has a “home” directory Files are separated from other users Cannot edit system data/configuration Often can’t even see system data

Basic Linux Administration – Linux User Basic File Structure Hard disk is divided into partitions

Usually a minimum of 2: / (root) and /home

Idea is to keep user data and system data separated to prevent problems

Users: 2 minimum Super user (root) At least one “regular” user

Linux Community

Linux is by its nature a community The OS and applications only move

forward by the help of many Help is a “HOW-TO” or a mailing list

away Google. groups are an excellent source

of information Linux Documentation Project is a huge

resource of “HOW-TO” documents –written by the community

Linux Software

Thousands of programs already run on Linux

Office suites, games, web development tools are probably the most lacking, although more are always developed

Basic File Structure

Hard disk is divided into partitions Usually a minimum of 2: / (root) and

/home Idea is to keep user data and system

data separated to prevent problems Users: 2 minimum

Super user (root) At least one “regular” user

Source Distribution Installation Requires source files, easily

downloadable Knowledge of command line interface Installation of basic compiler 95% of all programs are compiled with

GNU C++ compiler, freely available Understanding of the file system,

where to place files File/Directory Permissions

File Permissions

Every file and directory has three sets of permissions

Read (r) –can read the file Write (w) –can write, change and delete the

file Execute (x) –an executable script/file Permissions can then be set for three

different groups User –the person that owns (created) the file Group –the group the user belongs to Others –everyone else

OpenOffice –Sun Microsystems office suite http://www.openoffice.org

Samba –Windows connectivity client and server http://www.samba.org

Apache Web Server –the standard on the Internet http://www.apache.org

PHP scripting language –create dynamic web pages http://www.php.net

GIMP –powerful image program comparable to Photoshop http://www.gimp.org

MySQL Database –free, powerful, easy to use http://www.mysql.com