Get current DNS server on 16.04-server

nslookup can be used to get the DNS server that is being used.

Example:

$ nslookup www.google.com
Server:     10.0.0.1     <--This is the DNS server address.
Address:    10.0.0.1#53

Non-authoritative answer:
Name:   www.google.com
Address: 216.58.217.36

Hope this helps!

For the majority of applications,

less /etc/resolv.conf

should work. Otherwise, you can try,

dig xxxxxxxxx

replacing xxxxxxxx with any server of your choice. You should see what nameserver was used to look it up.

N.B.: Don't be surprised if it is 127.0.0.1 : this is your localhost, which probably means it's your router that is determining your nameserver.