CentOS 配置防火牆操作：
查詢防火牆狀態：
[root@localhost ~]# service iptables status
停止防火牆：
[root@localhost ~]# service iptables stop
啟動防火牆：
[root@localhost ~]# service iptables start
重啟防火牆：
[root@localhost ~]# service iptables restart
如何打開某個端口呢：
1. 進入防火牆配置文件：
[root@localhost ~]# vi /etc/sysconfig/iptables
2.例如要打開3306端口：
-A INPUT -m state --state NEW -m tcp -p tcp --dport 3306 -j ACCEPT
3.重啟防火牆：
service iptables restart
完整的配置文件如下：
# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -i eth0 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 3306 -j ACCEPT
-A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -p icmp -j ACCEPT
-A FORWARD -i lo -j ACCEPT
-A FORWARD -i eth0 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
如果想要關閉某個端口：在配置文件中去掉配置，重啟防火牆就好了