Fix "Could not reliably determine the server's fully qualified domain name" when starting Apache server on Ubuntu
Using Apache 2 development environment on your Ubuntu machine most likely involves looking at "Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName" message each time your machine boots. Here's how to make this irritating message disappear when starting Apache 2 server by specifying ServerName inside Apache 2 configuration files.
This error happens because your server doesn't have ServerName Apache 2 variable defined and reverse lookup on your IP address returns nothing. We can specify ServerName as 127.0.0.1 to make this message disappear. Just open your favorite terminal emulator and paste:
echo "ServerName 127.0.0.1" | sudo tee -a /etc/apache2/conf.d/server_name
Now you can restart your apache 2 server:
sudo service apache2 restart
You shouldn't have that message displayed ever again.