DNS Related Questions

Prompt: Address already in use

Please check if systemd-resolved exists on the local machine. Check as follows:

1. First check if the port is already occupied

ss -ltup

In Local Address:Port, check if there is a domain or program occupying port 53.

                                       
udp       UNCONN   0     0            127.0.0.54:domain           0.0.0.0:*         users:(("systemd-resolve",pid=556,fd=15))  
udp       UNCONN   0     0         127.0.0.53%lo:domain           0.0.0.0:*         users:(("systemd-resolve",pid=556,fd=13))  
tcp       LISTEN   0     4096         127.0.0.54:domain           0.0.0.0:*         users:(("systemd-resolve",pid=556,fd=16))  
tcp       LISTEN   0     4096      127.0.0.53%lo:domain           0.0.0.0:*         users:(("systemd-resolve",pid=556,fd=14))  
tcp       LISTEN   0     1024          127.0.0.1:39329            0.0.0.0:*         users:(("code-6609ac3d66",pid=196919,fd=9))

If you get similar results, then the local systemd-resolved service has occupied the port.
Use the command systemctl stop systemd-resolved to stop it and then you can start.

To completely disable the systemd-resolved service, please use:

systemctl stop systemd-resolved
systemctl disable systemd-resolved
systemctl mask systemd-resolved

To restore configuration:

systemctl unmask systemd-resolved
systemctl enable systemd-resolved
systemctl start systemd-resolved