You might have got the same error while you were restarting the Apache server on Ubuntu Linux.

* Starting web server apache2

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

Soltution: Edit the file in the following path,

vi /etc/apache2/httpd.conf

By default the file httpd.conf will be blank so put the entry as below

servername localhost

Now you can start the service without any error or warning,

/etc/init.d/apache2 start