Lets edit our httpd.conf, on CentOS 7.6 & Apache/2.4.6 it’s located at /etc/httpd/conf/httpd.conf
nano /etc/httpd/conf/httpd.conf
And edit our ServerName line/entry.
Restart httpd
service httpd restart
Could not reliably determine the server’s fully qualified domain name, using 127.0.0.1. Set the ‘ServerName’ directive