如何解决centos防火墙无法启动？
CentOS防火墙无法启动，在线服务器都需要开启防火墙服务，这是linux系统安全防护最直接有效方式。
1、如果出现
service iptables start service iptables restart
无法启动/重启防火墙时。
2、最佳的方法是修改配置文件
vi /etc/sysconfig/iptables [plain] view plaincopy # 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 -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT
然后再启动防火墙
service iptables start
查看防火墙服务
service iptables status
3、如果需要开启例外端口则，增加如下配置：
vi /etc/sysconfig/iptables [plain] view plaincopy # 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 -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
如上，增加了3306服务端口
如果需要关闭防火墙自动启动则
查看状态
chkconfig --list iptables
关闭自动启动
chkconfig iptables off
查看状态
chkconfig --list iptables
相关参考：centOS教程
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