1、查看防火墙状态

[root@instance-xfl1djr7 ~]# /etc/init.d/iptables status

2、启动/关闭防火墙

• 开启防火墙

[root@instance-xfl1djr7 ~]# service iptables start

• 关闭防火墙

[root@instance-xfl1djr7 ~]# service iptables stop

• 开机自启

开启： chkconfig iptables on
关闭： chkconfig iptables off

3、开放指定端口

• 比如我要开放3306三个端口，可以在/etc/sysconfig/iptables文件中添加三行信息，如下：

vi /etc/sysconfig/iptables

内容修改成如下：
# 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 -m state –state NEW -m tcp -p tcp –dport 3306 -j ACCEPT 

-A INPUT -j REJECT –reject-with icmp-host-prohibited 
-A FORWARD -j REJECT –reject-with icmp-host-prohibited 
COMMIT

• 修改后重启防火墙

service iptables restart