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

1. /etc/hosts
 127.0.0.1       localhost xxxxx

xxxxx is /etc/hostname

2./etc/apache2/httpd.conf

ServerName localhost


Reference:
http://stackoverflow.com/questions/9541460/httpd-could-not-reliably-determine-the-servers-fully-qualified-domain-name-us