The iptables-restore command is used to restore the iptables rule-set that was saved with the iptables-save command. It takes all the input from standard input and can't load from files as of writing this, unfortunately. This is the command syntax for iptables-restore:
iptables-restore [-c] [-n]
The -c argument restores the byte and packet counters and must be used if you want to restore counters that were previously saved with iptables-save. This argument may also be written in its long form --counters.
The -n argument tells iptables-restore to not overwrite the previously written rules in the table, or tables, that it is writing to. The default behavior of iptables-restore is to flush and destroy all previously inserted rules. The short -n argument may also be replaced with the longer format --noflush.
To load a rule-set with the iptables-restore command, we could do this in several ways, but we will mainly look at the simplest and most common way here.
cat /etc/iptables-save | iptables-restore -c
The following will also work:
iptables-restore -c < /etc/iptables-save
This would cat the rule-set located within the /etc/iptables-save file and then pipe it to iptables-restore which takes the rule-set on the standard input and then restores it, including byte and packet counters. It is that simple to begin with. This command could be varied until oblivion and we could show different piping possibilities, however, this is a bit out of the scope of this chapter, and hence we will skip that part and leave it as an exercise for the reader to experiment with.
The rule-set should now be loaded properly to kernel and everything should work. If not, you may possibly have run into a bug in these commands.