Apply rules

Use iptables-apply when possible:

_$: iptables-restore < file-with-rules  # Be careful!
_$: iptables-apply   < file-with-rules  # Allows you to go back if you messed up the configuration

In case iptables-apply complains about not finding the /etc/network/iptables file, copy your rules file to that location:

_$: cp file-with-rules /etc/network/iptables
_$: iptables-apply
_$: rm /etc/network/iptables

Save rules

_$: iptables-save > file-with-rules