The iptables firewall is the built-in firewall for protecting a Linux machine from online threats. But the settings are not save upon a re-boot. This is easily alleviated by installing the iptables-persistent package for Ubuntu. Once this is installed, you will be greeted with a screen that will ask you if you wish to save your iptables rules. Answer yes to both questions and the application will save your rules safely in case of a re-boot of the desktop or server the firewall is on.
Type this command to install this application.
sudo apt-get install iptables-persistent
There is another blog posting here: http://ekuric.wordpress.com/2013/05/05/iptables-persistent/. This page also describes the iptables-persistent package. This will be a great help for anyone who is using the iptables firewall on Linux.