CentOS7.4 关闭firewall防火墙，改用iptables
1.关闭默认的firewall防火墙
systemctl stop firewalld.service#停止firewall
systemctl disable firewalld.service#禁止firewall开机启动
firewall-cmd --state#查看默认防火墙状态（关闭后显示notrunning，开启后显示running）</span>
2.开启iptables
<span style="font-size:18px;">yum install iptables （根据centOS7的版本和内核，有些版本已经装过，可以跳过此命令）
yum install iptables-services
service iptables restart
chkconfig iptables on或者systemctl enable iptables.service开机自启</span>
3.编辑防火墙文件（开启了21,22,80,3306端口）
vim /etc/sysconfig/iptables
# sampleconfigurationforiptables service
# # you can edit thismanuallyoruse system-config-firewall
# # pleasedonotaskustoadd additional ports/servicestothisdefaultconfiguration
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --stateNEW-m tcp --dport21-j ACCEPT
-A INPUT -p tcp -m state --stateNEW-m tcp --dport22-j ACCEPT
-A INPUT -p tcp -m state --stateNEW-m tcp --dport80-j ACCEPT
-A INPUT -p tcp -m state --stateNEW-m tcp --dport3306-j ACCEPT
-A INPUT -j REJECT --reject-withicmp-host-prohibited
-A FORWARD -j REJECT --reject-withicmp-host-prohibited
COMMIT </span>
5.查看本机关于IPTABLES的设置情况
<span style="font-size:18px;">iptables -L -n</span>
