How to solve "iptables: Resource temporarily unavailable" error

If you see "iptables: Resource temporarily unavailable" error when restarting Advanced Policy Firewall (APF) on your Linux server, then take the following steps:

1. Add up some more RAM memory to your box
2. Reload your iptables:
/etc/init.d/iptables reload
3. Make sure your iptables get restarted without any errors:
service iptables restart
4. And finally restart your firewall:
apf -r