If you get this warning message when you start up Apache (apache2), this means that you are missing the ServerName setting inside apache2.conf. By default, the install of Apache in Debian is doesn’t include that setting in apache2.conf. The main reason is because they don’t know what your server name will be.
To fix:
Open up /etc/apache2/apache2.conf
Add the following line:
ServerName MyServer.com
Replace “MyServer” with your server name. Restart Apache.
Note:
Its only looking for the setting inside apache2.conf. It ignores the “ServerName” within a Virtual Host configuration block (such as in /etc/apache2/sites-enabled/000-default)
