After installing apache2, some time you face with the problems below when restart it's service
* Restarting web server apache2                                                                                 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName
 ... waiting apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName
This problems occur by the misstyping of localhost Ip address. Just resolve this issue by the following :

Edit file httpd.conf in /var/apache2/

sudo nano /etc/apache2/httpd.conf 

Add the following information :
ServerName localhost 

restart your apache2 service :
/etc/init.d/apache2 restart 


You can resolve this issues. Good luck !