Skype is a voip i.e. voice over internet telephony service which also provides you with the features like chat, video-voice chat, screen sharing, and calling telephone numbers at cheap call rates throughout the world almost in all the countries.

The major feature of skype is its online calling service between the PC is absolutely free and moreover has an excellent sound quality. Moreover the call rates are also very cheap.

You can install the skype on Linux as follows.

• Download the skype installation software from here .
• Change your directory to were you have saved the setup files which in our case is at Desktop of the root user.

#cd /root/Desktop

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What is a View in Oracle SQL Database?

A view is a logical table based on table or another view which is used to present the combinations of data present in the database. A view as itself doesn’t contain any data but it is more like a window through which the data from the tables can be viewed or changed. The table on which view is based is known as the base table and view is stored as a select statement in the data dictionary.

Advantages of Creating a View:-

• It restricts the data access to predefined tables and columns so that a database user can see only information relevant for him.

• It makes the complex queries easy.

• Provides the data independence.

• Can be used to present the different views of the same data.

There are majorly two types of views:-

1.    Simple Views

2.    Complex Views

The major difference b/w the two lies in the DML operations.

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Shell script is a series of command’s written in a plain text file. It is somewhat similar to the batch-file in MS-DOS but have much more power and functionality than MS-DOS batch file. The major advantage is that you don’t need to write the same set of instructions again, since you can execute it via your script file.  It is majorly used to automate the tasks of day to day life and moreover can be used to automate the system administration part.

Below is an example of a script file by which you can determine whether a file exists or not. This script is used to tell you only whether file exists or not, but not its location as to where it is located. For that you can use FIND OR LOCATE command. We have created a file named existence-of-file.sh you may create a file with some other name. But it is convenient to save the file with ( .sh ) extension so that at later point of time you can recognize that it is a script file. Also in below code whatever is in front of # is a comment.

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Mozilla thunderbird is the one of the most famous free open source, cross-platform e-mail and news client developed by the Mozilla foundation.  You can easily receive mail from different mail providers on your desktop and can even store these mails on your local desktop alone. Further you can also remain updated with latest new around the globe or locally by using it. Mozilla thunderbird is just like Microsoft outlook express with only difference is that it supports both IMAP and POP3.  And also unlike outlook express it is open source and can be used equally well on various platforms including Linux. You can simply install thunderbird on Linux by downloading its package from the Mozilla’s site.

Here is a link to Mozilla thunderbird package

http://www.mozillamessaging.com/en-US/thunderbird/

After downloading the package just follow the steps to install and configure an email client

• Navigate to the directory were you have downloaded the package (thunderbird-3.1.6.tar.bz2). In our case it is on the Desktop

# cd /root/Desktop

#ls

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Data Security And Encryption In Linux

Need for Security:-

• Password/Data Sniffing.
• Data Manipulation
• Authentication Manipulation

Insecure Traditional protocols

• telnet, FTP, POP3 etc: insecure passwords
• sendmail, NFS, Nis etc: Insecure information
• rsh, rcp etc: insecure authentication

The most common security must include fully secured Networking security, secure authentication, assurance of data integrity and privacy.

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