Could not reliably determine the server’s fully qualified domain name

I had a sever that every I restarted the httpd service I got “Could not reliably determine the server’s fully qualified domain name” To fix it I created a file called fqdn.conf in /etc/httpd/conf.d/

$sudo vi /etc/httpd/conf.d/fqdn.conf

and add:

ServerName mul1.hohenfels.com

Then

$sudo service httpd restart

$sudo systemctl restart httpd

And everything should come back up clean