CentOS切换为iptables防火墙
切换到iptables首先应该关掉默认的firewalld，然后安装iptables服务。
1、关闭firewall：
service firewalld stop
systemctl disable firewalld.service #禁止firewall开机启动
2、安装iptables防火墙
yum install iptables-services #安装
3、编辑iptables防火墙配置
vi /etc/sysconfig/iptables #编辑防火墙配置文件
下边是一个完整的配置文件：
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 22 -j ACCEPT #开放端口，复制一条改对应的端口就可以了 -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -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
:wq! #保存退出
service iptables start #开启
systemctl enable iptables.service #设置防火墙开机启动