Tài Liệu - Võ Tấn Dũng (votandung) Unit1 Linux ITC new

Linux IntroductionLecturer: Võ Tấn Dũng votandung@yahoo.com http://sites.google.com/site/votandungsg/ Information Technology College of HoChiMinh city Faculty of Information Technology

Linux Introduction

Lecturer: Võ Tấn Dũng

votandung@yahoo.com http://sites.google.com/site/votandungsg/

Information Technology College of HoChiMinh city

Faculty of Information Technology

Course: Fundamentals of Linux OS

Unit 1

Before Linux

• In 80’s, Microsoft’s DOS was the dominated OS for PC

• Apple MAC was better, but expensive

• UNIX was much better, but much, much more expensive

Only for minicomputer for commercial applications

• People was looking for a UNIX based system, which is

cheaper and can run on PC

• Both DOS, MAC and UNIX were proprietary, i.e., the source code of their kernel is protected

• No modification is possible without paying high license fees

What is Unix?

• A multi-task and multi-user Operating System

• Developed in 1969 at AT&T’s Bell Labs by

– Ken Thompson (Unix)

– Dennis Ritchie (C)

– Douglas Mcllroy (Pipes)

• Some other variants: System V, Solaris, SCO Unix, SunOS,

4.4BSD, FreeBSD, NetBSD, OpenBSD, BSDI,…

VÕ TẤN DŨNG

Beginning of Linux

Minix , a simplified version of UNIX that runs on PC

commercial use

Computer Science at the University of Helsinki,

developed the preliminary kernel of Linux, known as

Linux version 0.0.1

After that…

–Soon more than a hundred people joined the Linux camp

Then thousands Then hundreds of thousands

–It was licensed under GNU General Public License, thus

ensuring that the source codes will be free for all to copy,

study and to change

–Linux has been used for many computing platforms: PC,

PDA, Supercomputer,…

–Not only character user interface but graphical user interface

is available

–Commercial vendors moved in Linux itself to provide freely

distributed code They make their money by compiling up

various software and gathering them in a distributable format

VÕ TẤN DŨNG

• Many Linux Distributions

– Slackware (one of the oldest, simple and stable distro.)

– Redhat

• RHEL (commercially support)

• Fedora (free)

– CentOS (free RHEL, based in England)

– SuSe ( based in German)

– Gentoo (Source code based)

– Debian (one of the few called GNU/Linux)

– Ubuntu (based in South Africa)

– Knoppix (first LiveCD distro.)

– And now, ANDROID of Google

Linux Today

 Shell interprets the command and

request service from kernel

 Similar to DOS but DOS has only

one set of interface while Linux

can select different shell

– Bourne shell (bash)

– Korn shell

– C shell

 Different shell has similar but different functionality

 Bash is the default for Linux

 Graphical user interface of Linux is in fact an application

program work on the shell

Variety of Linux Shell

VÕ TẤN DŨNG

The File System

– Linux supports many file-systems: ext, ext2, ext3, xia, minix, umsdos, msdos, vfat, proc, smb, ncp, iso9660, sysv, hpfs,

affs,…

– Common Linux Subdirectories:

Some important directories

– The starting point (/) is called the root directory

– /usr: contains executable commands, system administration utilities, and library routines

– /etc: contains system configuration files

– /home: contains the user‘s home directory

– /dev: contains files which are pointers to device names

– /root : the root user's home directory

– /bin : important Linux commands available to the average user

– /boot : the files necessary for the system to boot

– /lib : contains system libraries

– /mnt : contains mount points When you temporarily load the contents

of a CD-ROM, USB drive or a HDD partition, you typically use a

special name under /mnt

– /sbin : contains essential commands that are only for the system

administrator

VÕ TẤN DŨNG

Log in your Linux system

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

account is defined in the /etc/passwd file

– The “root” account is the system administration account

– File /etc/passwd : each entry in this file is made up of seven fields

separated by a colon

– Placeholder, that is /etc/shadow file, it maintains the field for

the password The /etc/shadow file contains encrypted

passwords

– These two files can only be read by the system administrator

– Example: #cat /etc/passwd OR #cat /etc/shadow

Log in, log out

• Start up your computer, then type in your username and

password:

– login: (type in your username here)

– password: (type in your password here)

• If you want to log out your Linux current session, using exit

command or key-combination <Ctrl-D>:

– exit

– <ctrl-D>

VÕ TẤN DŨNG

• Using passwd command for changing the user password

$ passwd Changing password for cis1

Old password:

New password:

Retype new password:

Hashed database not in use, only /etc/passwd text file updated

$

Changing User Password

• whoami , tells you who is currently logging in to a

terminal

$ whoami user1

$

• To see more details about the user who is currently

• The who command, will tell you who are log-in right now

jlp tty0 sep 20 10:05

you tty2 sep 22 10:34

Current log-in users

[root@redhat9 tmpdocs]#

host name

If # , that means user root If $ , that means regular user (not user root)

• hostname command displays the name of the host

computer you have logged into

$hostname

redhat9

$

Viewing hostname

• To change the host name:

$hostname <type in a new name here>

VÕ TẤN DŨNG

Shutdown your Linux system

– Some CLI commands to shutdown your Linux: halt, poweroff,

reboot, shutdown, init 0

Examples:

#shutdown -r 5 “It will be rebooted in 5 minutes!”

#shutdown -h 3 “Your system will be turned off in 3 minutes“

Using runlevel

– A runlevel is a mode of operation of the Linux OS, that

provides a particular set of services

– File : /etc/inittab

– Using init command to switch between levels

VÕ TẤN DŨNG

Displaying Man Pages

commands

Command Format

man <name-of-a-command>

$ man cd

Reformatting page Wait done

CD(1) NAME

cd, chdir, pushd, popd, dirs - change working directory SYNOPSIS

Example:

VÕ TẤN DŨNG

Scrolling in Man Pages

while using the man command:

Command-Line Syntax

The general format for Linux commands is:

#command [option (s)] [argument[s]]

At the shell prompt, you can type commands

Commands are instructions which tell the system to

perform an action

VÕ TẤN DŨNG

Command-Line Syntax (cont.)

Examples:

ls -a -l /etc/mydir useradd -u 503 -g sales alan mkdir -p /mnt/ docs/xls/priv

cp -i sales.doc /mydoc cat /mnt/ploppydisk/baitap.txt head -6 /usr/dict/words

tar -xvf /home/backup.tar

Some Linux’s commands

mkdir – make directories

ls – list directory contents

cd – changes directories

pwd print name of current working directory

cp – copy files and directories

mv – move (rename) files

rm remove files or directories

find – search for files in a directory hierarchy

history – prints recently used commands

cat – concatenate files and print on the standard output

echo – display a line of text

wc print the number of newlines, words, and bytes in files

sort – sort lines of text files

su – change user ID or become superuser

VÕ TẤN DŨNG

Control Characters

Control characters are used to perform specific tasks such as

stopping and starting screen output When displayed on the

screen, the Control key is represented by the caret symbol (^) To enter a sequence of control characters, hold down the Control key and press the appropriate character on the keyboard

END OF UNIT 1

• remember to do your homework

(see http://sites.google.com/site/votandungsg/)