Introduction to Linux1
Transcript of Introduction to Linux1
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Lab 1
INTRODUCTION
TO
LINUX
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What is Computer
A computer is an electronic device that
accepts information in the form ofdigitalized data and manipulates it for some
result based on a program or sequence of
instructions on how the data is to beprocessed.
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The Computer is a programmable finite
state machine which can perform precise
arithmetic and logical operations.
A programmable finite state machine is
one that can take a fixed range of values.The computer is called programmable
because it can be instructed to perform
tasks within its capacity.
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Computer System
Hardware Software Livewire(User)
Computer System
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HARDWARE
The physical circuitry and components areknown as hardware.
The hardware is categorized into five blocks.
Namely
Input Unit
Arithmetic Logic Unit(ALU)Control Unit
Memory
Output Unit
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CRT Display
Keyboard
Mouse
The Box
CD-ROMDrive
Floppy
Disk
Drive
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Software
Application Software System Software
Software
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What is a System Software?A computer program that controls the system hardware
system and interacts with application software;
Example- operating system.What is an Application Software?Application software (sometimes shortened toapplication) is any program designed to perform a
specific function directly for the user or, in some cases,
for another application program. Typical types of
application software include: Word processing,Electronic spreadsheet, Database, Email reader, Web
browser, Graphics software and so on.
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Operating System?
It is a set of programs that act as an interfacebetween the user and the hardware.
It is a system software that lies between
computer hardware (disk, Memory, Processoretc.) and the Application programs (WordProcessors, Web Browsers, spread Sheetsetc.)
It controls and co-ordinate the operation of acomputer system.
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What OS does?
It loads itself into the memory-Booting.
It loads the user program in the memory.
It loads the data required by the program in thememory.
Interprets the program instruction one at a time.
Sends instruction to the output device to display
the result on the screen. Uses the resources like memory, input and
output devices properly and efficiently.
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Major OS Functions
User Interface
Job/Task Management
Data Management
Device Management
Security
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Types of OS
Single User OS
Multi User OS
Multi Tasking OS Multi Processing
Real Time OS
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Linux OS
Linux is a free Unix-like operatingsystem Developed under the GNUGeneral Public License
It is a multi-user, multitasking OS withsupport for Networking
The source code for Linux is freelyavailable to everyone.
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History of Development!
The development of Linux started fromUNIX.
UNIX is a trade mark of AT & T,originally developed by Ken Thompson,
Dennis Ritchie and others back in 1970srunning on mainframes andmicrocomputers.
It is a multitasking and multi user OS.
Unix is mostly used in servers and webservers.
It is written with C language
It is a foundation for many OS like Linux,Novell etc. Ken Thompson, 1943
Dennis Ritchie, 1941
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History continues
Linux OS uses Unix as the base and gives
further more facilities and applications.
It was first released by its inventor LinusTorvalds in 1991.
In Linux GUI is made having Unix as its
core.
Linux is the ultimate Unix.
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History continues
Many vendors purchased the source code andhave developed their own versions.
IBM, HP, Sun etc.
The source code was also made free to collegesand universities.
UC Berkeley, and MIT have been on the front edge of
development since the beginning. As a lot of variations are appeared in various
versions, IEEE comes with a standard POSIX.1(Portable Operating System Interface for UNIX).
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Linux Came into Picture!!!
The down side of UNIX is that it is proprietary big and
expensive, especially for PC version.
This is where Linux comes in.
It was designed to be small, fast and inexpensive with
every functionality available.
Originally created by Linus Tovalds of university of
Helsinki, Finlald in 1991 using no code from AT & T. But partially from scratch and partially from using publicly
available PC based implementation of UNIX called
MINIX.
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Linux released!!! Finally Towards the end of 1991
Linux was made public and in Nov.
1991 version 0.10 was released.
In Dec 1991 version 0.11 wasreleased.
At the same time Torvalds made
source code free on the Internet and
asked to work with it.
Today's version of Linux is 2.6.12.x.
and freely downloadable from
www.kernel.org.
The Big Boss!
Linus Torvalds,
1969
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Linux Distributions
Several Companies and Organizations began
gathering and packaging Linux software together
in to useable forms called distributions Now there are almost more than 350
distributions available around the world!
The most popular distributions areRed Hat, SuSe, Debian, Slackware, Mandrake etc.
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Features of LINUX
Multi-user Multiple users can logged into and work on the system at the
same time.
Each user will have their own private area in the system where
they can customize their environments for use.
Multitasking
Can have many programs running at the same time for the user
Also Linux runs many of the system processes in the background
called Daemon processes, which remain ready for ever to serve
the request of a user. Graphical User Interface.
Hardware Support
Linux supports all most all well known hardware.
Networking Support
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Advantages!
Documentations like books, tutorials are freely
available for download in the web.
Also a project called Linux Documentation
project provides free materials
www.tldp.org
Help is available by professionals around theworld round the clock.
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Linux Commands
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What is a Command?
A command is an instruction telling acomputer to do something.
A command is an instruction to
perform a task in operating system
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Linux Commands
A command prompt looks like
[cs0203@linuxserver cpp]$
cs0203: user name linuxserver: machine name
cpp: current working directory
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Guidelines
All commands must always be entered in smallcase letters
Between command name and the options theremust be a space
The options are usually preceded by a - sign
Two or more options may be combined like
lsa -l as lsal
To repeat a command up-down arrow keys may beused
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Basic Linux Commands dateprints current date and time
Syntax:[cs0203@linuxserver cpp]$ date
O/P: Tue Nov 22 15:24:12 IST 2005
cal
Prints calander of current year Syntax:
[cs0203@linuxserver cpp]$cal 11 2005
O/P: November 2005
Su Mo Tu We Th Fr Sa1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
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Basic Linux Commands
who (who am i) Displays the users logged in to the system
Syntax
[cs0203@linuxserver cpp]$who
O/P:ee05183 pts/278 Nov 22 15:23 (192.168.5.8)
et05428 pts/286 Nov 22 15:29 (192.168.5.9)
ee05410 pts/285 Nov 22 15:29 (192.168.5.10)
pwd Displays present working directory
Syntax:
[cs0203@linuxserver cpp]$pwd
O/P: /home/cs0230/cpp
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Basic Linux Commands
ls Lists files and folders of current directory
O/P:
squid.conf fontforge-20040529-1.i386.rpm squid.newsquid.conf golden collection mukeshpics
squidGuard.log indlinuxtcp ls -l
Long listing of files and folders of current directory
O/P:
-rw-r--r-- 1 cs01 cs01 2474 Oct 1 17:25 maze.cpp
drwxrwxr-x 4 cs01 cs01 4096 Oct 25 11:19 linux
lsal
List all files in the current working directory in long listing formatshowing permissions, ownership, size, and time and date stamp
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Getting Help
man
Displays the system manual
Command man displays information on man
Syntax :
[cs0203@linuxserver cpp]$man ls
info
Displays information in a different format
Command info displays information on man
Syntax:
[cs0203@linuxserver cpp]$info date
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What is a File?Any named collection of information stored on a disk.
Application programs and documents are examples of
files. You make a file when you create information (such
as text or graphics) using a program, give the material a
name and save it on a disk.
What is a Directory?It is a special kind of file that points to or contains
others files and directories. Directories can benested to any depth. Some software may refer to
directories and subdirectories by other names, such
as, folders, lockers, file drawer, etc.
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Creating a file touch
Creates an empty file Syntax:
[cs0203@linuxserver cpp]$touch test.txt
cat Used to create and display a file.
cat : displays file contentsSyntax:[cs0203@linuxserver cpp]$cat firstfile.txt
cat > : creates a file and save with ctrl+d
Syntax:[cs0203@linuxserver cpp]$cat > firstfile.txt
cat file1 file2 > file3 : concatenates contents of files file1 & file2 & storeit in file3(if it is not exist then newly created otherwise content of file3 is
overridden)Syntax:[cs0203@linuxserver cpp]$cat file1 file2 > file3
Cat file1 file2 >> file3 :concatenates content of files ,if file3 exist&contents some information then new content is appended.
Syntax:[cs0203@cat file1 file2 >>file3
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File related commands
mkdir
To create directory(s)
Syntax:
[cs0203@linuxserver cpp]$mkdir silicon cd
To change directory
Syntax:
[cs0203@linuxserver cpp]$cd silicon file
Display file type
Syntax:
[cs0203@linuxserver cpp]$file firstfile
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What is Path?Path is the specification of a file or directory in a hierarchical file
system using pathname separators ("/" in Unix)between
directories. The pathname tells the shell where in the directorytree to find a file. Files may be referred to by absolute pathname(also called full or complete pathname) orrelative pathname.Absolute path is a path relative to the root directory, the topmostnode of a hierarchical file system. Its first character must be a
pathname separator, e.g., the Unix forward slash . absolute
pathname is the full specification of a path beginning with the root
directory and including all directory levels the system passes
through to locate the file.relative pathname is the location of the file or directory relative tothe directory in which the user is currently located (the current
working directory).
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File commands contd. cp
Copies srcfile to destfile If destination file is present then overwrites
Else creates a new file with name destfile
Syntax:
[cs0203@linuxserver cpp]$cp test.c test1.c
clear
Clears the screen
Syntax:
[cs0203@linuxserver cpp]$clear shutdown
Shuts the system down.
Syntax:
[cs0203@linuxserver cpp]$shutdown
File commands contd
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File commands contd. mv
moves/renames a file or directory
mv : renaming
mv : moves to path directory
mv : moves with renaming
Syntax:
[cs0203@linuxserver cpp]$mv test.txt test1.c
rm
Removes/deletes a file
Syntax:
[cs0203@linuxserver cpp]$rm test.c rmdir
Removes/deletes an empty directory
Syntax:
[cs0203@linuxserver cpp]$rmdir cpp
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Some VI Commands
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vi is a screen-oriented text editor written by Bill Joy in 1976 .The name vi is derived from the shortest unambiguous
abbreviation for the command visual in ex.
vi editor works in 3 different modes
>> Command Mode
>> Insert Mode
>> Last Line Mode
INTRODUCTION TO VI EDITOR
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:Insert Mode
Command Mode
Last Line Mode
i, I, o, O, a, A
EscEsc or Enter
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[cs0203@linuxserver cpp]$vi
e.g [cs0203@linuxserver cpp]$vi firstcprog.cIf the file firstcprog.c exists then this command open the fileotherwise it will be created.
when vi editor starts it will be in command mode. To type we
must have to go to Insert mode.
Command to invoke Vi editor
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Operation on Vi Editor
Delete Operation
First move the cursor so that it covers the first character of thegroup you want to delete, then type the desired command as
below
x Delete only the current character D Delete to the end of the line
db Delete from the current character to the beginning of thecurrent word
de Delete from the current character to the end of thecurrent word
dd Delete the current line
dw Delete from the current character to the beginning of thenext word
[n]dd delete n lines from the current line.
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Operation on Vi Editor
Copy & Paste operation
p
Paste the specified buffer after the current cursor position or
line. If no buffer is specified (with the " command.) then 'p' uses
the general buffer.P
Paste the specified buffer before the current cursor position or
line. If no buffer is specified (with the " command.) then 'P' uses
the general buffer.
y
Yank(copy) the current line.
[n]yy
Yank n lines from the current line. The buffer can be specified
with the " command. If no buffer is specified, then the
general buffer is used.
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A
Append at the end of the current line.I
Insert from the beginning of a line.
O
(letter oh) Enterinsertmode in a new line above the current
cursor position.
aEnterinsertmode, the characters typed in will be inserted after
the current cursor position. A count inserts all the text that had
been inserted that many times.
i
Enterinsertmode, the characters typed in will be inserted before the
current cursor position. A count inserts all the text that had been
inserted that many times.
o
Enterinsertmode in a new line below the current cursor position.
Inserting New Text ( Change mode from Command to Insert)
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ZZ (in Command Mode)
Exit the editor, saving if any changes were made.
:w (in Last Line Mode)
Save the current document
:q (in Last Line Mode)
Exit the editor if no modification is made.
:wq (in Last Line Mode)
Exit the editor, saving if any changes were made.
:q! (in Last Line Mode)Exit the editor, without saving if any changes were made.
:wq! (in Last Line Mode)
Exit the editor, overrides the files saving if any changes
were made.
Saving and Quitti ng
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Search and Replace
As files become longer, you may need assistancelocating a particular instance of text.
Simple search / enter
n: next forward, N: next backward
Search-Exclusions/wild-card search
The special characters are: $ . * [ ] ^ \.The slash (/) starts a forward search. And (?) to
search backwards.
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Search and Replace
finding instances of a given string and replacingthem with a new string. It has the following
: line1, line2s/ oldstring / newstring
You specify the range of text for the search-and-
replace command with the line numbers line1 and line2. If you only give line1 and omit the comma,
then the command only affects that line. If you
give no line numbers, the command affects the
current line. The search-and-replace commandonly finds the first occurrence ofoldstringon theline.
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Search and Replace
You can repeat a search-and-replace on the currentline by typing an ampersand (&). To repeat it on adifferent line or group of lines, type:
: linenumber& or
: line1,line2&
The command g (for global) can be used with s
(substitute) to find and replace every occurrenceof a string pattern in an entire file.
The syntax of the global command is:
:g/string/commands
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Search and Replace
The global command finds each line in the filethat hasstringin it and then applies the commandsto it. You can combine the global and substitute itin the following manner:
:g/oldstring/s//newstring/g
You dont need to put oldstringin the searchstring part of the substitute command because theeditor already has the pattern from the globalcommand.
When specifying oldstring, you can use the specialcharacters as explained in the section SpecialCharacters. vi does not recognize specialcharacters in newstring, since it is performing are lacement not a search.
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Miscellaneous
u - undo last change U - undo all changes to the current line
J - join current line and the line below it
. - repeat the last command
:! - command invoke an external "command"
:%s/frog/toad/ -Replace the first occurrence of
"frog" with "toad" for all lines in the file.
dG - delete to end of the file
1G - move to the beginning of file . . .
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Set Command
set nu: This command is used to associate line numberswith the file On which you are working.
Syntax:
[esc]:set nu
Set ic:This command is used to ignore the case while
searching a pattern in the file.
Syntax:[esc]:set ic