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Transcript of Rootsan Technologies Pvt Ltd Linux Modul033
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Welcome to RedHat Linux
RH033
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Hardware Requirements
Pentium Pro or better with 256 MB RAMOr
64-bit Intel/AMD with 512 MB RAM
2-6 GB disk space
Bootable CD
Other processor architectures supported
Itanium 2, IBM Power, IBM Mainframe
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Lesson 1 Fundamentals of
Linux
IntroductionLinux is an open source operating system with
highly advanced features.
Topics
Brief History of Linux
Why is Linux?Linux Distributions
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Brief History of Linux
Linux was originally developed by LinusTorvald in 1991.
Linux is distributed under the GNU licenses.
GNU stands for Gnu Not UNIX, it is an opensource movement started by RichardStallman in the year 1984.
The main aim of GNU is to provide the O.Sand its source code freely.
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Why Linux?
Linux is an Open Source Software
Multi-user and multi-tasking
Supports most of modern PC hardware
Fully supported distribution
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Linux Distributions
To install Linux, choose a Linux Distribution
A distribution is the Linux kernel, plus aninstallation program, plus some set of
applications
There are four general distributions RedHat SuSE Mandriva Linux Debian
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Linux Distributions
The Red Hat and SuSE distributions are produced by
companies by the same names.
They aim at providing an easy installation procedure, andfor a pleasant desktop experience. They are also good asservers, sold in boxes, with an installation CD and printed
manual. Both can also be downloaded via the network.
Mandriva Linux (also known as Mandrake Linux) wasoriginated by Gael Duval.
Mandriva Linux is also notable for compiling its packages
with optimizations for Pentium-class and more advancedprocessors which are incompatible with older CPU versionssuch as 386 and 486.
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Linux Distributions
The Debian distribution is produced by avolunteer organization.
Its installation is less easy: You have to
answer questions during the installation theother distributions deduce automatically.Nothing complicated as such, but requiringunderstanding of and information abouthardware most PC users don't want to worryabout.
On the other hand, after installation, Debian
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Logging In and GeneralOrientation
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Module 2 Logging In and
General Orientation
IntroductionIn Linux, a terminal session starts by
logging in through the terminal. When theuser logs in for the first time, the user
account is set and provided with apassword.
Topics Typical terminal session Concept of Login and Logout Opening of Shell Prompt Command Line Format
Basic commands vi Editor
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A Typical Terminal Session
Provides login prompt to the user
Linux has two modes of terminals
Graphical User InterfaceCharacter User Interface
Linux has seven terminals by default (F1 F6)
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Logging In and Out
A Graphical login screen Graphical Logout Session
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Opening a Shell Prompt
Snapshot
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Command Line Format
Pattern of issuing the command
The commands are separated with optionsusing spaces and symbols.
The options are usually prefixed with thehyphen ( - )
Command line has three basic parts Command Options Arguments
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Shell Interpretation
Shell prompt accepts commands to perform various functions like:Execute commands
Variable assignment
Variable substitution
Filename generationI/O redirection
Pipelines
Command substitution
Interpretive Programming language
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Basic Commands
vi opens a text editor
rm remove files
mv move or rename the files
cp copy the files
rmdir removes the directory
pwd display present working
exit or logout leave the session
man command Read man pages on command
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vi Editor
vi (visual) editor was written in 1976 by BillJoy at the University of California, Berkeley.
vi uses a small amount of memory, which
allows efficient operation when the networkis busy.
vi is the only editor which provides basic textediting capabilities.
There are three modes of operation for vi.
They are: Command mode
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Usage of vi Editor
A text editor is a program used to edit files thatare composed of text which can be a
Simple regular text
The source code of a program orConfiguration file
The vi text editor
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Lab Exercises
Type vi editor and get the vi session
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Navigating the File Systems
d l i i h
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Module 4 Navigating the
File SystemsIntroduction
A file system is the methods and the data structures that anoperating system uses to keep track of files.
Topics
The Tree Structure
The File System Hierarchy
Path Names
Basic File System Commands
Create and Remove Directories
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Th T St t
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The Tree Structure
Linux File Structure
Example:/home/condron/source/xntp
Th Fil S t Hi h
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The File System Hierarchy
File System Hierarchy Standard (FHS)
The directories and files noted here are small subsets of those specifiedby the FHS document.
The /dev/ Directory
The /etc/ Directory
The /lib/ Directory
The /mnt/ Directory
The /opt/ Directory
The /proc/ Directory
The /sbin/ Directory
P th N
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Path Names
A PATH is an environment variable that is a
list of directories that the operating systemlooks in to find commands issued by theuser.
Example 1: # whereis ls
ls: /bin/ls /usr/share/man/man1/ls.1.gz
There are two types of path names
Relative Path
Absolute Path
Contd
P th N
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Path Names
Absolute path
Accessing a particular directory or file from the otherlocation, by typing the full details of path.
Absolute path starts with the root (/) directory. It
includes all directories and sub-directories. A relative path starts in your present working directory.
Relative path
Accessing a particular directory or file from samelocation, by typing the file or directory name.
In the case of relative path, the path does not start
with a slash.
B i Fil S t C d
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Basic File System Commands
pwd It displays the users present
working directory.
ls Lists the contents of the files
and directories
cd Changes and also opens thedirectory.
cat It combines files and print onthe standard output
find Command The find command
C t d R
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Create and Remove
Directories Creating directories
Use mkdir command to create a new directory
Syntax
# mkdir
Example: mkdir dir1
Removing directories There are two commands you can use for removing
directories. rmdir
rm -r
L b E i
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Lab Exercise
How will you create a new directory?
Use rm r to remove the existing directory.
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Managing Files
Mod le 5 Managing Files
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Module 5 Managing Files
Introduction
On a Linux system, everything is a file;if something is not a file, it is a process.
Topics
What is a File?
File CharacteristicsWhat can we do with Files?
What is a File?
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What is a File?
A file is a container for data or link to a
device.
Every file has a name and may hold datathat resides on a disk.
A file is a name and the associated data isstored on a mass storage device. It is a
stream of data bytes.
The different types of files are: Regular files
Can be text, data and drawings. Executable ro rams.
File Characteristics
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[root@localhost root]# ls -l
total 1872
-rw-r--r-- 1 root root 1134 Sep 28 12:31 anaconda-ks.cfg
drwxr-xr-x 3 root root 4096 Oct 3 15:29 Desktop
drwx------ 8 root root 4096 Oct 3 15:15 evolution
-rw-r--r-- 1 root root 47186 Sep 28 12:30 install.log
-rw-r--r-- 1 root root 3436 Sep 28 12:30 install.log.syslogdrwxr-xr-x 3 root root 4096 Oct 1 12:48 intro-linux
-rw------- 1 root root 1832960 Oct 1 12:42 intro-linux.html.tar
drwx------ 7 root root 4096 Oct 1 14:45 Mail
-rw-r--r-- 1 root root 51 Oct 3 12:44 new.txt
[root@localhost root]#
File Characteristics
A file has several characteristics associated
with it. They can be displayed using the ls lcommand as shown below:
Contd
File Characteristics
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File Characteristics
Example:
-rw-r--r-- 1 root root 1134 Sep 2812:31 anaconda-ks.cfg0 1 2 3 4 5
6 7 The explanation of output is as follows:
File Type regular file d directory l link file c character special file b block special file p pseudo special file Permissions No. Of links to the File
Contd
File Characteristics
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File Characteristics
Owner
Group
File Size BytesTime Stamp
File Name
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What can we do with Files?
A file is a collection of data, stored on disk
and that can be manipulated by listing thecontents in the directory, changing thelocations of files and directories, viewingfiles, creating and editing files, moving,copying and deleting files.
The user can also create directories, change
directories, delete directories and view PDFfiles.
A directory is also a file that acts as a folder
for other files.
Manipulating files and
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Manipulating files and
directoriesCopying files
Copying files and directories is done using the cp command. Thecp command is used to copy the files and directories from the specifiedsource to the specified destination. The user can copy a file into thedirectory, but under a different name.
Syntax
cp
Example: # cp file1 dir1
Removing files
The rm command is used to remove single files, rmdir toremove empty directories (Use ls -a to check whether a directory isempty or not). The rm command also has options for removing non-empty directories with all their subdirectories, read the Info pages fordifferent options of rm command.
Contd
Manipulating files and
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Manipulating files and
directoriesMoving and Renaming files
The mv command is used to move a file from its source to anylocation within the file structure.
Example of moving a file: # mv file1 /iiht/file1
Example of moving a file: # mv file1 /iiht/file1
The above example says, the file file1 is moved to a different directory iiht.
The mv command is also used to rename a file or a directory
Example of renaming a directory: # mv iiht dir1
Contd
Manipulating files and
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Manipulating files and
directoriesLinking filesA link is nothing more than a way of matching two or more file names to
the same set of file data. There are two ways to achieve this:
Hard link
Soft link
Hard link
Associates two or more file names with the same inode. Hard links sharethe same data blocks on the hard disk, while they continue to behave asindependent files.
Soft link or symbolic link (or symlink)
Soft link is a small file that is a pointer to another file. A symbolic linkcontains the path to the target file instead of a physical location on the hard disk.Since inodes are not used in this system, soft links can span across partitions.
Lab Exercise
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Lab Exercise
Create a directory by name testand create
the files file1 file2 and file3, createhardlinkfor file1 to new file data.
Differentiate deleting hard link files and softlink files.
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File Permission and Access
Module 6 File Permission
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Module 6 File Permission
and Access Introduction
Linux is a multi-user system where users can assigndifferent access permission to their files. Access permissionscan be set per file for owner, group and others on the basisof read (r), write (w) and execute permissions (x).
Topics File Permissions and Access
Types of Access
Who has to Access to a File?
Access Control Lists
Contd
File Permissions and Access
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File Permissions and Access
Every file is owned by a particular user.
File permissions specifies who has the access to file andwhat type of access the user has.
On a Linux system, there is typically more than one userthat provides a mechanism known as file permissions(rwx), which protect user files from accessing by otherusers.
Types of permissions r read
w write
x execute
Contd
File Permissions and Access
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File Permissions and Access
read permission
The read permission lets a user read the contents of the file.For directories, read permission lets the user list the contents ofthe directory (using ls).
write permisisonThe write permission lets the user write and modify the file.
For directories, write permission lets the user create new files ordelete files within the directory.
execute permissionThe execute permission lets the user run the file as a program
or shell script (if the file is a program or shell script). Fordirectories, execute permission lets the user open the directory.
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Types of Access
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Types of Access
Default file permissions
By default, the Linux system assigns certain permissions to anewly created file. The maximum permissions that we can set for anordinary file is 666 and for directories and an executable files is 777.
The default file permission for an ordinary user is 664 and for
root it is 644.
Displaying the umask
The default umask file permissions for ordinary users are 002and for root it is 022.
where, 002 imply masking write permission for others and
022 implies masking write permission for the group and others.
Contd
Types of Access
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Displaying the umask
To display the default mask use the umaskcommand.
Example
# umask
Displaying the default umask value
Types of Access
Contd
Types of Access
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Changing the umask
To change the default umask use the command Syntax
# umask
Example: umask 004
Types of Access
Who has to Access a File?
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Access permission user(owner) group
Who has to Access a File?
The owner and the root have the main
access rights over a file.Example
First column gives the access permissions to theuser, group and others.
Second column shows the user or owner of thefile.
Third column shows the group to which the filebelongs.
Contd
Who has to Access a File?
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Changing permissions
chmod command
chmod changes the access permissions accordingto the options for directories and files.
Syntax
# chmod o+w
Who has to Access a File?
Contd
Who has to Access a File?
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Who has to Access a File?
The chmod command can be used with
alphanumeric or numeric options. Example of symbolic method
chmod u+rw,g-rwx,o-rwx file1 The above example, adds the read and write permission to the
user (owner) removes the read, write and execute permission
from the group to which the file belongs and removes the read,write and execute permissions for others.
Example of numeric method
# chmod 600 file1 6 indicates user (owner), 0 indicates group and the last number
0 indicates others.
Contd
Who has to Access a File?
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Who has to Access a File?
Changing ownership
chown command chown changes the owner and group of the file and
directory.
Syntax # chown
Example # chown user1 file1.txt
Contd
Who has to Access a File?
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Special File Permissions
There are three types of special file permissions
set user identity (SUID)
set group identity (SGID)
sticky bit
Who has to Access a File?
Contd
Who has to Access a File?
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Who has to Access a File?
Contd
SUID or setuid
It is represented by the character s in the user permission
field.
When this mode is set on an executable file, the other userscan login and run the executable file.
The roots id is set to the process.
Syntax
#chmod u+s
where,
u user
s - suid
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Who has to Access a File?
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Who has to Access a File?
Sticky bit
If the sticky bit is set on directory, even others can read andwrite the data to the file, but can not delete the file except theowner.
Syntax
#chmod o+t
where,
o others
t - sticky bit
Example: # chmod o+t /tmp
Contd
Access Control Lists (ACLs)
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Access Control Lists (ACLs)
ACL is an object associated with a file and contains entries
specifying the access that individual users or groups ofusers have to the file.
It provides a simple way of granting or denying access for aspecified user or groups of users on single file at the same
time.
Using the chmod command the user can set permissions toowner, group or others.
Using ACL, the owner can set the different permissions on asingle file for different users.
Contd
Access Control Lists (ACLs)
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Contd
Setting ACL using Setfacl
setfacl - set file access control lists
Syntax setfacl u::
Access Control Lists (ACLs)
Access Control Lists (ACLs)
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Access Control Lists (ACLs)
Contd
Getting ACL using getfacl
The getfacl displays the file name, owner, thegroup, and the Access Control List (ACL).
Syntax
# getfacl
Access Control Lists (ACLs)
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Contd
o o ( )
Copying ACL
The acls can be copied to any files, for which thefiles get the same acl permissions from its sourcefile.
Syntax
getfacl | setfacl --set-file= -
where,
--set-file options set the acl of a file or a directory
Lab Exercise
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Change the permission of the following file
using chmod command.-rwx-rw-r-- file2.txt
From the following example change thepermissions to
User read, write, execute
Group read and execute Others - only execute
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Shell Basics
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What is a Shell?
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A shell manages the interaction between the
system and its users.A shell is a program which takes user input
(e.g. commands which you type) andtranslates them into instructions that theoperating system can understand.The shell allows the user to handle a system
in a very flexible way.
Contd
What is a Shell?
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Contd
Shell Features
Command history The command history buffer stores the commands you enter and
let you display them at any time.
Command aliases
The command aliases feature lets you abbreviate long commandlines or rename commands.
File name completion
The file name completion feature saves typing by allowing you to
enter a portion of the file name. When you press the tab/esc key,the shell will complete the file name for you.
Command line editing
This allows you to retrieve a previously entered command and editit.
What is a Shell?
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Contd
Types of shells
sh or Bourne Shell This is the basic shell, a small program with few features. This
shell does not support any of the shell features such ashistory, command line completion, command line editing.
bash or Bourne Again shell The standard GNU shell, intuitive and flexible. bash is the
standard shell for common users. This shell is a so-calledsuperset of the Bourne shell. This means that the BourneAgain shell is compatible with the Bourne shell: commands
that work in sh, also work in bash.
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Types of shells
csh or C shell: This shell has a syntax that resembles that of the highly popular C
programming language and thus preferred by programmers.
tcsh or Turbo C shell
This shell is based on csh but also has programmable filenamecompletion, command-line editing, a history mechanism and otherfeatures lacking in csh.
ksh or the Korn shell:
This shell is a superset of sh. It also features built-in arithmeticevaluation and advanced scripting capabilities similar to those foundin powerful programming languages such as awk, sed and perl.
Aliasing
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Contd
g
The command aliases allow the user to abbreviate long
command lines with small names easy to use and type.
Creating Aliases
To create aliases, use the alias command. The format of the aliascommand is:
Syntax
alias aliasname=command
The aliasname entry specifies the name you want to use.
The alias helps for alternate names for complicated commands.
Example:
[root@localhost root]# alias cls=clear
[root@localhost root]# cls
Aliasing
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Display Aliases
To display alias definitions, enter the followingcommand:
# alias
Remove Aliases To remove an alias for the current login session,
use the unalias command.
The general format of the unalias command is the
following: unalias
g
File Name Completion
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File name completion is one of the most useful features of
the Linux command line.
The shell lets you enter a portion of a file name orpathname at the shell prompt and the shell automaticallywill match and complete the name.
Example # vi us Press Enter
Then the entire file name will be completed as follows if itis unique name,
# vi user123.filnename.txt
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User profiles
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The user profile is a personalized settings of the user
and the shell script and gets executed whenever theuser logins.
The profile can be classified into:
System wide
The changes to system wide profile will effect the workenvironment of all users. These files are available in /etc.
User Specific
User specific profiles effect the work environment of only
that particular user and it stores in the home directory of each user.
What Happens At Login
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When a user logs into a system it executes the
start up scripts in the following sequence:/etc/profile sets the environmental variables andsettings for all users.
/etc/profile.d. runs the login script for all users.
~/.bash_profile - sets the environmental variables andsettings for particular user.
~/.bashrc - runs the login script for particular user.
/etc/bashrc - sets the environmental variables for bashshell.
Variables
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A variable is a label that has a value.
Variables are used to configure the shell.
To set a variable in the shell, use an equal sign toassign it a value. If the variable does not already exist,
it is created.
Example A new variable is defined as follows: $ MYVARIABLE=hello
To display the value of a variable, prefix the variablesname with a $ symbol.
Contd
Variables
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Types of Variables
There are two types of variables Shell variables or local variables
Environment variables
Shell variables or local variables are available only to the currentshell which is used to configure shell.
Environment variables are available to all shells and used toconfigure other commands. e keyboard arrows. To move up anddown in the history command shell. It helps to change the mainvariables like prompt settings, color settings by changing within theprofile to make effect for the entire settings.
Contd
Variables
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Display variable
set command is used to display the local andenvironment variables in a system.
env command is used to display onlyenvironmental variable.
There are two commonly used Variables Local variables
Environment variables
Contd
Variables
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Local variables
HISTFILESIZE - specifies the number of commands ofhistory to be saved when the shell exit.
COLUMNS- sets the width of the terminal.
LINES- sets the height of the terminal.
Environment variables HOME- path to the user home directory.
LANG- sets default language.
PWD- present working directory.
PATH- the path for the command locations. These variables are stored in the profile file (.bashrc).
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Module 8 Shell Advanced
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FeaturesIntroduction
In Linux systems, the shells are often referredto as command line interfaces. The shell capabilitiesprovide a configurable environment allowing the usersto modify commands and prompts.
Topics Shell Substitution Capabilities
Setting Shell Variables
Quoting Characters File Name Generationss
Shell Substitution Capabilities
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Substitution capabilities are used to speed
up command line typing and execution.
The shell substitutions are of three types:
Variable Substitution
Command substitution
Tilde Substitution
Contd
Shell Substitution Capabilities
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Variable Substitution
Variable substitution is assigning the absolute pathof a file or directory to any variable. This allowsthe user to access the directory or file fromanywhere in the file hierarchy.
Syntax: =$
Example: myfile=$HOME/file1
Contd
Shell Substitution Capabilities
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Command substitution
Command substitution is the mechanism used toreplace a command with its output, within thesame command line.
Syntax: =$(command)
Example: mydir=$ (pwd)
Contd
Shell Substitution Capabilities
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Tilde Substitution
A tilde is replaced for the quick reference ofhome directory.
Syntax: ~
Example: ls ~
Setting Shell Variables
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The new variable can be created and assigned to an
existing environmental variable such as path.
The new value replaces the old value in theenvironment and the same can be displayed by
using the display value commands.Syntax
=
Example
myfile_name=/root/file1
Contd
Setting Shell Variables
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Displaying variable values
The variables can be displayed by using $.
It can be local variable (assigned by the user) or
environmental variable (default variable). All setting variables can be displayed by using thecommand set.
Quoting Characters
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There are some characters in the Unix system and
each has the meaning for the shell and is called asspecial characters. The special characters are:
-
$
#
*
< >
Quoting removes the special meaning of the above
characters. The quoting characters are: \ Backslash
Single quotes
Double quotes Contd
Quoting Characters
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Contd
Backslash ( \ )
Backslash removes the special meaning of thecharacter immediately following the backslash.
Quoting Characters
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Single quotes ( )
The single quote is used to preserve the literalvalue of special character enclosed within the quotes.
Contd
Quoting Characters
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Double quotes ( )
Double quotes removes the special meaning ofall the characters except \ , $ (variable name), $(command).
File Name Generation
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The file name generation has the timesaving feature for
typing the filenames. This feature is called file name
generation or filename expansion.
Advantages of file name generation
File name generating characters are interpreted by the shell.
The command operates on the generated file names. The shell will generate file names that satisfy the requested pattern.
File name generation is done before the command is executed.
The special characters that are interpreted by the shell forfile name generation are: ? Matches any single character except a leading dot
* Matches zero or more characters except a leading dot
Contd
File Name Generation
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Usage of the special character ?
Contd
File Name Generation
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Usage of the special character *
Lab Exercise
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Give one example on usage of single quotes
command with the variable substitution
Display the files which has 9 characters andwith the extension .jpg
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Input and Output Redirection
Module 9 Input and OutputRedirection
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Redirection Introduction
One important thing you have to know to understand I/O
redirection is file descriptors. There are three types of I/O, calleda file descriptor. They are standard input, standard output,standard error.
Topics Input Redirection
Output Redirection
Error Redirection
Filter
Pipes
Input Redirection
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The standard input (stdin) by default is any text
entered from the keyboard.
Standard input can be redirected through the use ofcommand line argument and redirection operators (like
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Output Redirection
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The default standard output (stdout) is the display
screen.
The command line programs automatically send theiroutput to the screen.
Standard output can be redirected through the use ofcommand line argument and redirection operators (like>).
The standard output can be redirected from the screento any file or to the printer.
Contd
Output Redirection
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Example of output redirection
# ls > list.file
Syntax# command > (file name
Error Redirection
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By default the standard error (stderr) displays on
the terminal and can be redirected into a file,printer and any other program.
Standard error can be redirected with the
standard error redirection operator (i.e 2>, 2>>).
The error messages can be redirected to any file,so that the error messages will not appear on the
screen and it is written to the file.
Contd
Error Redirection
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Example of error redirection
# ll myfile 2>error_message
Syntaxcommand (filename) 2> (filename)
Common RedirectionOperators
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Operators There are two common redirection operators
>
>>
> operator sends the input of command or file to theother file as standard input, overwriting the existingfile.
> > operator sends the input of command or file to the
other file as standard input, appending text to anexisting file, instead of overwriting the file.
Contd
Common RedirectionOperators
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OperatorsUsage of > operator
Syntax# cat > (filename)
Contd
Common RedirectionOperators
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Contd
Usage of the >> operatorOperators
Filters
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Filters take standard input and perform an operation upon it andsend the results to standard output.
Example for filters: grep root /etc/passwd
The grep command is used to filter the root user from the /etc/passwd
file.
Pipes
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A pipe is a mechanism for interprocess communication.
The data written to the pipe by one process can be readby another process. It is handled in a first-in, first-out(FIFO) order.
Pipes ( | ) let you redirected output from one commandto become input to another command.
Example: simple pipe with morels -l | more
Contd
Pipes
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The tee command
The tee command copies the standard input to standard outputand also to any files given with an argument.
This is useful when you want not only to send some data down apipe, but also to save a copy.
If a file being written which does not already exist, it is created.
If a file being written which already exists, the data contained isoverwritten unless the -a option (appends the standard input to
the given files rather than overwriting)
Contd
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Lab Exercise
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Filter and display the word blue from the file
my_sortfile
Sort and redirect the data from one file toanother
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Networking in Linux
Networking in Linux
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IntroductionA computer network is defined as a number of systems that
are connected to each other and exchange information across thenetwork connection. The system network is configured by settingthe IP address which is assigned by the system administrator.The IP address provides base services for transmitting databetween networks in TCP/IP (Transmission control
protocol/Internet protocol).
Topics
Network Connectivity
IP address Accessing Remote system
Transferring files
Internet configuration
Networking in Linux
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The Linux system can be connected to the network with the helpof network hardware.
Network hardware can be LAN (Local area network) card, cables,hub/switch or router. To configure the network for the system,TCP/IP (Transmission Control Protocol/Internet Protocol) addressis required from the system administrator.
The IP address can also be obtained from the DHCP (Dynamichost configuration protocol) server configured by the systemadministrator.
When the system is connected to the network, the resources canbe shared and data can be transferred among the systems.
The LAN services (telnet, SSH - Secure Shell, FTP File transferprotocol) enables the file transfer and remote login to the system.
IP Address
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An IP address is a 32 bit binary number usuallyrepresented as 4 decimal values, each representing 8
bits, in the range 0 to 255 (known as octets) separatedby decimal points.
Every system in network is assigned a uniqueidentifying number called IP address.
It is used in order to identify and communicate withdifferent systems present in the network.
The data is sent across the network and contains a
source and destination IP address.
Example:
10.10.1.240
130.130.1.10
192.168.1.200
IP Address
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Configuring IP address
The system can be a part of network byconfiguring the IP address. The IP address can be setby two options in CUI mode and GUI mode.
Static IP
Dynamic IP (DHCP)
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IP Address
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Static IP address in CUI mode
Configuration of the static IP address
Syntax
Type the command # netconfig (Press Enterkey) at the command prompt in the terminal window.
IP Address
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network service
Syntax# service network restart
IP Address
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# ifconfig
IP Address
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# ping
IP Address
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Dynamic IP address in CUI mode
Configuration of the dynamic IP address
Syntax
# netconfig (Press Enter key)
IP Address
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Static IP address in GUI mode
Network configuration in static IP
IP Address
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Dynamic IP address in GUI mode
DHCP settings
IP Address
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Host NameA hostname is the unique name assigned to each host
on the network. The hostname is used to identify a particularIP address. Hostnames are used by various naming systemslike telnet, ssh, FTP, GFTP, NIS and DNS.
There are three ways to resolve host names to IPaddresses on a Linux system:
/etc/hosts
DNS (Domain name service)
NIS (Network information service)
Contd
IP Address
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etc/hosts is a configuration file maintained locally on each hostto resolve hostnames to IP addresses. On a small network, it is
easy to maintain the name resolution of hostnames toaddresses. When adding or removing hosts, or reassigning IPaddresses, the user have to update the /etc/hosts file.
DNS (Domain name service) will resolve the host names into
IP addresses in a large network.
NIS (Network information service) provides a central point ofadministration for common configuration files like /etc/passwd,
/etc/hosts. It preserves the consistency of the configuration
files across all the systems on the network. It simplifiesconfiguration file updates considerably.
Accessing Remote System
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Systems in the network can be accessed remotely withhelp of network connectivity and using IP addresses in
two ways:
Telnet
SSH
Telnet
Telnet is a terminal program for TCP/IP networks such as the Internet.
The telnet program runs on your computer and connects your system tothe other system present in the network.
To start a telnet session, you must log in to other system by entering avalid username and password of the other system.
Contd
Accessing Remote System
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Contd
telnet session
Syntax# telnet
Accessing Remote System
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SSHSSH is a program for logging into a remote machine and
for executing commands on a remote machine
The root user can login through SSH and execute thesystem administrative command.
ssh command
Syntaxssh
Transferring files
Files can be transferred among various systems in
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Files can be transferred among various systems inthe network by using FTP, GFTP and SCP (secure
copy). FTP FTP (File transfer protocol) is a program that allows you to
transfer the files between computers present in the network. Itcan also transfer the files among different operating systems.
Example: Linux to Linux, Linux to Windows, Windows to Linux.
Syntax
# lftp
Transferring files
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GFTP
GFTP (Graphical file transfer protocol) is the toolused for uploading and downloading the files in agraphical mode.
GFTP (Graphical file transfer protocol)session
Contd
Transferring files
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SCP (secure copy)
The scp command is used to copy the files fromother system present in network.
Syntax
# scp :
Example: scp file1 192.168.1.171:/root
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Internet configuration
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Step 2: Proxy configuration
Contd
Internet configuration
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Step 3: Setting the proxy IP and the port
number
Contd
Internet configuration
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Contd
Step 4: Verifying the Internet connectivity
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Internet configuration
C i i h h d
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Connection to internet through modem
Lab Exercise
H t fi th IP dd i CUI d ? A
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How to configure the IP address in CUI mode? Assumethat your system administrator or lab in-charge has given
you the IP Address as 192.168.1.60?
Check your system to be a part of network andcommunicate with other systems present in the work
Configure your system with Dynamic IP Address usingDHCP
Name the command to copy the files among the system
in the network with out using ftp?
Name the command to copy the files among the systemin the network with out using ftp?
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Process Control
Module 11 Process Control
I t d ti
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Introduction A process is a running occurrence of a program,including all variables and other conditions. It is anexecuting program.
Each process contains a system wide unique processnumber (PID- Process Identification).
Topics Identifying Process
Managing Process
Background Processing Putting Jobs in Background
The operating system will execute the processes by
Identifying Process
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The operating system will execute the processes bydefault and the user can also create a process.
The process can be identified which is in executionalong with its PID (process identification number).
Process creation
Processes are created with the fork system call (theoperation of creating a new process is called forking).
Example: vi
Contd
Vi i th i i
Identifying Process
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Viewing the process origin
The pstree command is used to display theprocess origin.
Contd
Identifying Process
Vie ing the c ent p ocess
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Viewing the current process
The ps command is one of the tools for visualizingprocesses. It displays the current working shell. Sinceps command does not give detailed information aboutthe process, the grep command in a pipe is used toselect a particular process out of the list of all
processes.
The bg command is used to check and
Managing Process
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The bg command is used to check and
move a job to background
Contd
Example for foreground
Managing Process
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Example for foreground
Contd
Managing Process
Process Scheduling
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Process Scheduling
The Linux kernel uses a process scheduler to decide which process
has to be executed first. It is done by using process priority.
Scheduling Priorities
Every process has a scheduling priority. The operating systemdetermines the priority of a process based on nice value method.
To calculate this priority is difficult, but users can affect the priorityby setting the nice value. The niceness value is the numberranging from -20 (highest priority) to 19 (lowest priority) It has adefault value of zero. Process with a high priority gets to run moreoften, while the low priority background tasks, run less frequently.
Contd
Priorities for programs
Managing Process
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Priorities for programs
The nice values of active processes can be viewed using
the ps command with the l or f option for long output.
Example for nice command:
The nice command is used to modify the default niceness
value. To set the niceness value to a different value, usethe n option:
Example:
Contd
Showing priorities of different process
Managing Process
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Contd
Showing priorities of different process
Managing Process
Usage of top command
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Contd
Usage of top command
The top program displays all the system and usersprocess priorities running in all the terminals.
The process running on your system is updated once inevery five seconds.
A process in the running state is highlighted.
Managing Process
Altering priorities of running programs
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Contd
Altering priorities of running programs
The users can reduce the priority of currentlyrunning jobs using the renice command. Only thesuperuser is permitted to move up the priority ofcurrently running processes.
Example of renice command
Managing Process
Terminating the process
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Contd
Terminating the process
The process is terminated when it receives asignal.
There are multiple signals that the user can send
to a process. The kill command is used to send a signal to aprocess.
The command kill -l shows a list of signals which
the user wants to terminate.
killall command will perform an orderly
Managing Process
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Contd
killall command will perform an orderly
shutdown of the process.
killing a process
Managing Process
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killing a process
Background Processing
A background process is the child of the process.
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A background process is the child of the process.
It refers to processes that are run with a relatively low priority,require little or no input, and produce a minimum of output.
The background is also used for long tasks that requiremassive amount of computation and thus CPU time.
Daemon (Disk and execution Monitor)
A daemon is a background process that is considered to runindependently, with little or no user interference.
Example: Apache web server http daemon (httpd)
Putting Jobs in Background
The shell offers a feature called job control which allows
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The shell offers a feature called job control which allowseasy handling of multiple processes. This mechanism
switches processes between the foreground and thebackground. Using this system, programs can also bestarted in the background immediately.
putting jobs in background
jobs command is used to verify the background process
Contd
Putting Jobs in Background
Suspending a process
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Suspending a process
A process can be suspended temporarily withoutbeing killed. Suppose that & symbol is missed outby mistake, use ^z and the process will besuspended.
The process still exists but is idling. To resume theprocess in the background type the bg command(background).
Lab Exercise
Create a process viwith filename and send the process to
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p pbackground and check background process
Check the background running process and bring it to the foreground
How to send running process to the background and bring it back tothe foreground?
Start a Process using find command with the priority of -18
Display and manage the priorities with the single command
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Offline File Storage
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Storage files to Media
Backing up of a system is the most major task to be
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g p y jperformed by a system administrator.
Computers have the major advantage of storing thedata, which makes it significant.
Backups are important because of the possibility ofloss of data.
The possibility of data loss can be by:
File system corruption
Accidental removal of files
Hardware failures
System crashContd
Backup Media
Storage files to Media
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Contd
p
The following are some of the methods of back up through
media floppy disks
Tapes
removable hard disks
rewritable CD-ROMs
Backup tools
tar
dd
Dump cpio
Storage files to Media
Backup using tar command
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Contd
An archiving program designed to store and extract files from an
archive file known as a tarfile. The tar is the most commonly usedcommand for the backup.
tar options
tar cvf (creating the tar file)
tar tvf (listing the contents of tar file)
tar xvf (extracting the contents of tar file)
where,
c create
t list
x extract
v verbose
f file
Backup using dd command
Storage files to Media
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Contd
p g
dd copies a file from source to destination. It copies aninput file (if) file and sends the result to the output file (of) whichconverts and formats according to the options.
Syntax
# dd if= of=
Exampledd if=bootdisk.img of=/dev/fd0
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Storage files to Media
Example:
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Contd
a pdump -0 f /home_dumps/mydumps /home
where,-0 - dump level (full backup)
-f - write a backup to file
Storage files to Media
Backup using restore command
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Contd
The restore command is used to view and restore the dumpfile.
Syntax:# restore -
Example: restore if mydumps
where,
-i is interactive restoration
-f is read backup from file
Backup using cpio command
Storage files to Media
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Contd
p g p
The cpio command is a tool for creating and extractingarchives, or copying files from one place to another,which contains other files and information about them,such as their file name, owner, timestamps, and access
permissions.
It handles a number of cpio formats as well as readingand writing tar files. The archive can be another file on
the disk, a magnetic tape, or a pipe.
cpio has three operating modes.
Storage files to Media
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Contd
copy-out mode, cpio copies files into an archive.
copy-in mode, cpio copies files out of an archive or liststhe archive contents.
copy-pass mode, cpio copies files from one directorytree to another, combining the copy-out and copy-in
steps without actually using an archive.
Syntax for creating the cpio file
Storage files to Media
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Contd
find (source file name) | cpio (options) > (target file name)
Example: find file1 | cpio -o > file1_back.cpio
Syntax for extracting the cpio file
cat | cpio (options)
Example:
cat file1_back.cpio | cpio idvm
where,
d make directories
i extract m modification time
o create
v verbose
Storage files to Media
Compression tools
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Contd
Zipzip is a compression and file packaging utility. The program is
useful for packaging a set of files for distribution, archiving files andsaving disk space by temporarily compressing unused files ordirectories. The zip program puts one or more compressed files into asingle zip archive, along with information about the files. An entiredirectory structure can be packed into a zip archive with a singlecommand.
Syntaxzip
Example:zip install install.log
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Storage files to Media
Gzip
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Contd
By default, gzip keeps the original file name and
timestamp in the compressed file. These are used whendecompressing the file with the N option. The mainadvantage of gzip over compress is it has a better
compression capacity than other compression tools.
Syntax
gzip
Example
gzip install.log
Gunzipd h f l d b k l
Storage files to Media
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Contd
gunzip decompress the files created by gzip. It takes a list
of files on its command line and replaces each file ending with.gz, -gz, .z, -z, _z or .Z and which begins with the correctnumber with an uncompressed file without the originalextension. gunzip also recognizes the special extensions .tgz and.taz as shortcuts for .tar.gz and .tar.Z respectively.
Syntax
gunzip
Example: gunzip install.log.gz
Storage files to Media
Bzip2b i 2 i bl k ti fil It t li t f fil
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Contd
bzip2 is a block-sorting file compressor. It expects a list of file
names to accompany the command-line tools. Each file is replacedby a compressed version of itself, with the nameoriginal_name.bz2. Each compressed file has the same modificationdate, permissions and when possible ownership as the correspondingoriginal, so that these properties can be correctly restored atdecompression time.
Syntaxbzip2
Example:bzip2 install.log
Storage files to Media
Bunzip2bunzip2 (or bzip2 d) decompresses all specified files bzip2
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bunzip2 (or bzip2 -d) decompresses all specified files. bzip2
attempts to guess the filename for the decompressed file from that ofthe compressed file. If the file does not end in one of the recognizedendings, .bz2, .bz, .tbz2 or .tbz, bzip2 gives an error message that itcannot guess the name of the original file, and uses the original namewith .out.
Syntaxbunzip
Example:
bunzip install.log.bz2
Backup any desired directory using tar command
Lab Exercise
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Compress the file mydata from the data directoryand uncompress into a new directory by name
backup usingzip and unzip commands
Backup the /tmp directory into a new directory byname tmp_backup using dump command