Dig is a DNS lookup utility that can be useful for checking your DNS is answering queries correctly.
One can install the dig tool with the following command
sudo apt-get install dnsutils
If you want to query your current default DNS for a hostname, then simply enter the command below:
If you want to query a specific DNS, such as one you just set up, then one needs to specify it like below (substituting the IP):
dig my.domain.com @192.168.1.1
Alternatively, you can use a hostname for the nameserver, rather than the IP address, like below:
dig my.domain.com @ns1.mydomain.com
Below is an example of the ouput from such a query.
It may be important to know that the part with
;; Server: xxx.xxx.xxx.xxx is the IP address of the DNS server that responded. This is an easy way to figure out which DNS server you are using if you do not know.