Docker Setup Debugging: failed to bind host port 0.0.0.0:53/tcp: address already in use

Error:

Error response from daemon: failed to set up container networking: driver failed programming external connectivity on endpoint adguardhome-adguardhome-1 (6ba42dd568275667aa21718570b420addc374b5f53ab7e50da263c472679c4b3): failed to bind host port 0.0.0.0:53/tcp: address already in use

Hypotheses from error:

As the error obviously stated, port 53 is already in use by some other service.

Solution:

To check what service was being used in port 53, I used;

fuser 53/tcp

If you want more information from fuser you can also use the -v flag, i.e:

fuser -v 53/tcp

systemd-resolved is the OS’s built-in DNS stub resolver which binds to port 53. Docker cannot bind AdGuard to port 53 because it’s already taken.

Since AdGuard, the service I want using port 53, is already a DNS resolver, I disabled systemd-resolve with;

sudo systemctl disable --now systemd-resolved

Then,

sudo rm /etc/resolv.conf
echo "nameserver 1.1.1.1" | sudo tee /etc/resolv.conf

This ensures Ubuntu itself still has internet.

I restarted my service and it loaded perfectly.