This error is usually harmless. Sometimes you don’t require a complex /etc/hosts file that includes all your virtual hosts.

172.0.0.1 localhost.localdomain localhost
127.0.1.1 blogs

When running:

service apache2 restart

You might get this error:

AH00557: apache2: apr_sockaddr_info_get() failed for blogs
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1. Set the 'ServerName' directive globally to suppress this message

A quick solution to this problem:

vim /etc/apache2/apache2.conf
# Insert at the end of the file
ServerName localhost

service apache2 restart
 * Restarting web server apache2 [ OK ]