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Linux Shell Scripting Cookbook

You're reading from Linux Shell Scripting Cookbook Do amazing things with the shell and automate tedious tasks

Product type Paperback

Published in May 2017

Publisher

ISBN-13 9781785881985

Length 552 pages

Edition 3rd Edition

Tools

Linux

Concepts

Shell Scripting

Authors (3):

Clif Flynt

Sarath Lakshman

Shantanu Tushar

View More author details

Table of Contents (20) Chapters

Title Page

Credits

About the Authors

About the Reviewer

www.PacktPub.com

Customer Feedback

Preface

1. Shell Something Out FREE CHAPTER

2. Have a Good Command

3. File In, File Out

4. Texting and Driving

5. Tangled Web? Not At All!

6. Repository Management

7. The Backup Plan

8. The Old-Boy Network

9. Put On the Monitors Cap

10. Administration Calls

11. Tracing the Clues

12. Tuning a Linux System

13. Containers, Virtual Machines, and the Cloud

Basic firewall using iptables

A firewall is a network service that is used to filter network traffic for unwanted traffic, block it, and allow the desired traffic to pass. The standard firewall tool for Linux is iptables, which is integrated into the kernel in recent versions.

How to do it...

iptables is present by default on all modern Linux distributions. It's easy to configure for common scenarios:

If don't want to contact a given site (for example, a known malware site), you can block traffic to that IP address:

        #iptables -A OUTPUT -d 8.8.8.8 -j DROP

If you use PING 8.8.8.8 in another terminal, then by running the iptables command, you will see this:

        PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
        64 bytes from 8.8.8.8: icmp_req=1 ttl=56 time=221 ms
        64 bytes from 8.8.8.8: icmp_req=2 ttl=56 time=221 ms
        ping: sendmsg: Operation not permitted
        ping: sendmsg: Operation not permitted

Here, the ping fails the third time because we used the iptables command...

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Authors (3)

Clif Flynt

Clif Flynt

Clif Flynt has been programming computers since 1970, administering Linux/Unix systems since 1985, and writing since he was 9 years old. He's active in the Tcl/Tk and Linux user communities. He speaks frequently at technical conferences and user groups. He owns and runs Noumena Corporation, where he develops custom software and delivers training sessions. His applications have been used by organizations ranging from one manstartups to the US Navy. These applications range from distributed simulation systems to tools to help fiction authors write better (Editomat). He has trained programmers on fourcontinents. When not working with computers, Clif plays guitar, writes fiction experiments with new technologies, and plays with his wife's cats. He's the author of Tcl/Tk: A Developer's Guide by Morgan Kauffman, 2012, as well as several papers, and magazine articles. His poetry and fiction have been published in smalljournals, including Write to Meow by Grey Wolfe Press, 2015.

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Sarath Lakshman

Sarath Lakshman

Sarath Lakshman is a 27 year old who was bitten by the Linux bug during his teenage years. He is a software engineer working in ZCloud engineering group at Zynga, India. He is a life hacker who loves to explore innovations. He is a GNU/Linux enthusiast and hactivist of free and open source software. He spends most of his time hacking with computers and having fun with his great friends. Sarath is well known as the developer of SLYNUX (2005) - a user friendly GNU/Linux distribution for Linux newbies. The free and open source software projects he has contributed to are PiTiVi Video editor, SLYNUX GNU/Linux distro, Swathantra Malayalam Computing, School-Admin, Istanbul, and the Pardus Project. He has authored many articles for the Linux For You magazine on various domains of FOSS technologies. He had made a contribution to several different open source projects during his multiple Google Summer of Code projects. Currently, he is exploring his passion about scalable distributed systems in his spare time. Sarath can be reached via his website.

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Shantanu Tushar

Shantanu Tushar

Shantanu Tushar is an advanced GNU/Linux user since his college days. He works as an application developer and contributes to the software in the KDE projects. Shantanu has been fascinated by computers since he was a child, and spent most of his high school time writing C code to perform daily activities. Since he started using GNU/Linux, he has been using shell scripts to make the computer do all the hard work for him. He also takes time to visit students at various colleges to introduce them to the power of Free Software, including its various tools. Shantanu is a well-known contributor in the KDE community and works on Calligra, Gluon and the Plasma subprojects. He looks after maintaining Calligra Active - KDE's offie document viewer for tablets, Plasma Media Center, and the Gluon Player. One day, he believes, programming will be so easy that everybody will love to write programs for their computers. Shantanu can be reached by e-mail on [email protected], shantanutushar on Identi.ca/Twitter, or his website.

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