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GNU/Linux Basic Guide
This 255-page guide will provide you with the keys to understand the philosophy of free software, teach you how to use and handle it, and give you the tools required to move easily in the world of GNU/Linux. Many users and administrators will be taking their first steps with this GNU/Linux Basic guide and it will show you how to approach and solve the problems you encounter.
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By salemeni at 2011-08-03 06:46
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The Domain Name System (DNS) is a hierarchical naming system built on a distributed database for computers, services, or any resource connected to the Internet or a private network. Most importantly, it translates domain names meaningful to humans into the numerical identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide.
An often-used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses. For example, the domain name www.example.com translates to the addresses 192.0.32.10 (IPv4) and 2620:0:2d0:200::10 (IPv6).[from Wikipedia ]
This tutorial explains how to use OpenDNS, a great alternative to DNS servers of ISPs, which offer many advantages for the user.
1- OpenDNS on Linux
Open a terminal as root and run the following commands:
Quote:
cp /etc/resolv.conf /etc/resolv.conf.save
echo "nameserver 208.67.222.222" > /etc/resolv.conf
echo "nameserver 208.67.220.220" >> /etc/resolv.conf
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If you have a router that is also a DHCP server on your home network or you are on a corporate network, it will then reconfigure it so that it uses the OpenDNS addresses (Primary DNS: 208.67.222.222 and secondary DNS : 208.67.220.220) and it propagates to all machines located on the network.
More help on configuring OpenDNS is available here:
https://www.opendns.com/start
- To activate or not the correction of typing errors (google.cmo → google.com).
- Create shortcuts based on a single keyword. Once created, users can simply type keywords in the address bar of their browser to get directly to the desired site.
2. Benefits of OpenDNS
In addition to using the DNS service, it is also possible to open an account at OpenDNS, in order to have access to a management console that allows you for example:
- To obtain usage statistics such as number of DNS queries, or clear view of network activity.
- To choose several levels of security: anti-fishing, anti-pornography, or block the illegal networks. It is also possible to block certain areas directly.
Note that when you want to join a domain name that does not exist, you are redirected to an OpenDNS page that serves as a search engine (this is thanks to the ads found on this page OpenDNS earns money).
After several weeks of use, the service seems very reliable (no break) and very secure because they are reacting very quickly to the fault which affected DNS servers lately.
However, contrary to what one can read everywhere, OpenDNS is faster than the DNS of my ISP. Using the dig command lets put this into evidence.
Duration of a DNS query with OpenDNS:
Duration of a DNS query with the DNS of my ISP:
A human user, does not see the difference (7 msec).
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Public DNS server response times can be tested via http://www.willemijns.com/dns.htm.
A script for testing response times of ISP, OpenDNS and Level3 public DNS servers is at http://pastebin.com/U0VBG96q. It has BSNL (Indian ISP) server IP addresses hard-coded so they need to be manually changed to the user's ISP's.