In order to resolve this we will need to turn off the new dnsdist which runs via the initctl.
The upgrade of dnsdist has removed /etc/init.d/dnsdist and dnsdist is now controlled by init in the following location /etc/init/dnsdist.conf
“initctl start/stop dnsdist”
If the dnsdist.conf file exists in /etc/init/ it is processed by the Upstart process management daemon on boot, therefore starting dnsdist for any customer that gets the upgraded dnsdist package.
Details of the issue:
IF a customer is using pdns-recursor on port 53 and then upgrades to 6.3.1 onwards, dnsdist will therefore run prior to pdns-recursor and will prevent pdns-recursor from starting. This is differing config to our default running configuration on 6.2.5 and below as our default config has dnsdist disabled. This will therefore cause system issues for customers with this type of configuration.