So, I've been facing some DNS issues with my Ubuntu box and needed to do some debugging. While I was certain that my router was assigning the Google DNS servers (8.8.8.8 and 8.8.4.4) via DHCP to my machine, I needed to make sure that they were actually being used. Usually, I would be able to tell by looking at the output of /etc/resolv.conf oslt. However what I found in resolv.conf was
nameserver 127.0.0.53
options edns0 trust-ad
Using tools like dig also resulted in the nameserver being listed as 127.0.0.53. Googling around informed me that my Linux box was operating a DNS caching server locally. But how do I go about finding out which server this caching server was querying to resolve domains? Apparently, the answer is by using:
resolvectl status
which outputs a whole host of information including:
Link 2 (enp0s25)
Current Scopes: DNS
DefaultRoute setting: yes
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Current DNS Server: 8.8.8.8
DNS Servers: 8.8.8.8
8.8.4.4
DNS Domain: ~.
IOW, the DNS servers my system was using were the Google servers.
Hope this helps :)
Edit:
Disabling this local caching server can be done on Ubuntu by following the steps outlined here.