To disable the firewall (i.e., iptables) in Linux CentOS (or RedHat):
$ sudo /etc/init.d/iptables stop
If you also need to disable it from starting automatically at OS boot:
$ sudo chkconfig iptables off
To turn it back on:
$ sudo /etc/init.d/iptables start
and also add it to autostart:
$ sudo chkconfig iptables on
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