Issue the following command:

service apache2 restart

or

apachectl -k restart 

Ifrestarting the web server on a live website, it should be done gracefully.

A graceful restart tells the web sever to finish any active connections before restarting.

• This means that active visitors to the site will be able to finish downloading anything already in progress before the server restarts.

sudo /etc/init.d/apache2 graceful