One of the most useful utilities that hosts and ISPs and internet engineers use, is WHOIS.
This utility has a golden feature – it will show you, definitively, what the definitive name servers for a domain is.
Usage is simple, simply type this into the command line of a Linux computer:
whois example.com
How look for the name server information.
You can narrow it down like so, but be very careful, because not all servers report name server as the actual name server information, so rather look at the entire output to be sure. We’ll update the grep command as we discover more.
root@cpl:/# whois example.com | grep -i "name server" Name Server: A.IANA-SERVERS.NET Name Server: B.IANA-SERVERS.NET
There is no other record of the name server information, this is the only record. You can trust it. If it’s wrong, it’s not going to work.
Recently, when we tried to do WHOIS on a non-internet connected computer, this happened:
➜ ~ whois example.com getaddrinfo(whois.nic.host): Name or service not know
We find that interesting because it appears our Ubuntu / Mint Linux box is using whois.nic.host as the root database querying engine. I can only imagine how powerful and resilient and redundant this server must be. And how connected to the core of the internet it is.