Sometimes you need to disable the firewall in Linux from the command line. A good example is when you create a Xen virtual machine & configure VNC access. By default, the VM will boot up in init level 3 which is text mode and doesn’t have a graphical desktop. After you configure VNC access, you will not be able to connect since the firewall is on by default. You can disable the firewall from the command line as follows as root:
service iptables save
service iptables stop
chkconfig iptables off
The first command service iptable save, saves the current state of the firewall. The next command, service iptables stop, stops the firewall. Finally, the chkconfig iptables off command, turns off the firewall at boot time so it will not become active again.