端口映射命令(80>8080)：
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
重启后会失效。
保存命令：
service iptables save
centos7没有该命令：
# service iptables save
The service command supports only basic LSB actions (start, stop, restart, try-restart, reload,
force-reload, status). For other actions, please try to use systemctl.
解决方法：
1.先执行如下命令：
systemctl stop firewalld
systemctl mask firewalld
2.安装iptables services
yum install iptables-services
3.设置开机启动
systemctl enable iptables
4.重启iptables service
systemctl restart iptables
5.执行保存配置命令
service iptables save