Можно сделать вот так
vim /etc/network/interfaces
iface lo inet loopback
post-up /sbin/iptables-restore < /etc/firewall.conf
можно так
iptables-save > /etc/firewall.conf
vim /etc/network/if-up.d/iptables
#!/bin/sh
iptables-restore < /etc/firewall.conf
chmod +x /etc/network/if-up.d/iptables
или так
vim /etc/rc.local
iptables-restore < /etc/firewall.conf
