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JohnMerlino
Asked: 2013-04-23 08:23:45 +0800 CST

Why would I install a DNS server on my Ubuntu server?

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When you install Ubuntu server, the default Ubuntu server will only store the core system, but there is an option to add additional server roles. One of these is a "DNS Server".

From what I read, when you add this choice to your installation, Ubuntu adds the bind9 and bind9-doc packages to your system. These packages provide the Bind 9 DNS server and its documentation. Now in fact a DNS server is simply a technology that takes a host name and automatically finds the IP address for that host on the Internet. Whenever you purchase a domain, for example, on Godaddy, you have the option on their website to point that hostname at your public IP address. It's that simple. So why would anyone need to set up a DNS server on their Ubuntu installation?

dns

3 Answers

  1. Best Answer

    This is a very open question, there are lots of reasons to run a local DNS server. I'll give you why we use it at work:

    • As a cache to improve performance. Most of DNS queries are shared among lots of computers, if they are cached on our DNS server, clients don't need to connect to internet to resolve it, a much faster LAN connection will do it.
    • We want to name some computers that are only available in the LAN (i.e. on our network, you can't access then from the internet). Some of our servers can only be accessed from the internal network, we want our users to be able do it with a normal name using the same tools that they are used.
    • We give different IPs to some names: in a public (ISP) DNS our web server will resolve to our public (internet-facing) IP. When someone from the LAN ask our DNS to resolve its name we return our private IP.
    • To temporary ban some domain names, sometimes we need to ban for a couple of minutes some website, an easy way to do it is to change the IP it's pointing. As an example, a couple of months ago a virus was making lots of connections to a strange website. We changed it's name at the DNS forwarding it to a fake web server. Not only did we block it, we also get to quickly discover the infected machine by looking at the web server logs.
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  2. Some people run a local DNS server on their LAN for samba, apache, and Kerberos so that users on the LAN can use hostnames similar to what you describe for godaddy. Sounds as if you have no need for a local DNS server.

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  3. I actually also use GoDaddy, so I know what you're talking about.

    Here is the process of what happens so that a computer elsewhere in the world is able to visit your IP address using your domain name:

    1. You update your DNS zone file in GoDaddy with your IP address.
    2. The "relation" (between your IP address and domain name) is stored in the name servers you specified in your GoDaddy domain settings.
    3. These name servers then communicate with name servers all around the world to globally update this information so that people in Germany can type in your domain name and not be pointed to an old IP address still stored in their local name server.

    Of course, they say that "this takes time - 24-48 hours" but I usually see it move much quicker than this. American name servers will usually be updated with your new pointing information within like 10 minutes. Here is an extremely useful and very cool site for monitoring how your domain name is updated on name servers around the world: https://www.whatsmydns.net/

    The top practical reason an individual would want to set up a DNS server on their machine is because they have a dynamic IP address and want to automate the process of updating their name server with their IP address when it changes. I am in the process of learning how to do this but I suspect I can find a way using curl icanhazip.com and checking it against a text file with the results of my last check.

    Hope I provided some clarity!

    -Pierre

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