Change default document root for Apache 2 in Ubuntu

The default document root for Apache 2 is "/var/www/", if you input "http://localhost/" in your Web browser's URL address, you will get the contents of "index.html" in "/var/www/" directory.

If you want to change this default directory, modify the file "/etc/apache2/sites-available/default" (sudo gedit /etc/apache2/sites-available/default), and then, use the following two commands:

sudo apache2ctl -t

And then

sud apache2ctl restart

ps: sometimes you need to restart your apache server, here is the commands:

sudo /etc/init.d/apache2 stop
sudo /etc/init.d/apache2 start
sudo /etc/init.d/apache2 restart