Update：upgrade Ubuntu 20.04 LTS Rear，csf is not working，Prompt that iptables cannot be found：
This is because Ubuntu 20.04 LTS Changed iptables Related command position，The csf script is not updated in time。[……]
Firewall
we all know，Among Linux system has a very fast hardware firewall is called iptables，It can do far exceeds the scope of the firewall, but ......，usually，We only used it as a firewall to use。
but，If you just want a port policy，That does not seem to need to face iptables That lengthy configuration commands。From now on，I'll introduce you to the other a more[……]