This is happens when we pick the name of fqdn when firstly install Vesta and the name is different from the domain we bought. Then whenever we run the command sudo, we will get such error message.
To avoid showing this annoying message, we need to remove this registered fqdn by going to the /etc and edit the hostname file. Then paste in the following configuration:
127.0.0.1 localhost
127.0.1.1 your-fqdn.sth
Then restart the apache2 service by running this command: sudo service apache2 reload