The problem is when we restart apache on ubuntu 14, a strange message appeared.

root@izul-webserver:/var/www# /etc/init.d/apache2 restart
 * Restarting web server apache2                                                
 AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 103.21.95.22. Set the 'ServerName' directive globally to suppress this message [OK]

this is normal and not really problem.  If we insert a ‘ServerName localhost’ in either httpd.conf or apache2.conf in /etc/apache2 and restart apache the notice will disappear.

If you get this error:

apache2: Could not determine the server's fully qualified domain name, using 127.0.0.1 for ServerName

then use a text editor to create a new file,

sudo nano /etc/apache2/conf.d/fqdn

or

gksu "gedit /etc/apache2/conf.d/fqdn"

then add

ServerName localhost

to the file and save.

CAN BE DONE in a single command with the following:

echo "ServerName localhost" | sudo tee /etc/apache2/conf.d/fqdn

For on Ubuntu 14.04:

echo "ServerName localhost" | sudo tee /etc/apache2/conf-available/fqdn.conf
sudo a2enconf fqdn