在新安装的Linux系统中，防火墙默认是被禁掉的，一般也没有配置过任何防火墙的策略，所有不存在/etc/sysconfig/iptables文件。

原因：在新安装的Linux系统中，防火墙默认是被禁掉的，一般也没有配置过任何防火墙的策略，所有不存在/etc/sysconfig/iptables文件。

解决办法：
、随便写一条iptables命令配置个防火墙规则：如：

iptables -P OUTPUT ACCEPT

，进行保存

service iptables save

，service iptables restart

异常

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

With RHEL  / CentOS , firewalld was introduced to manage iptables. IMHO, firewalld is more suited for workstations than for server environments.

It is possible to go back to a more classic iptables setup. First, stop and mask the firewalld service:

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systemctl stop firewalld
systemctl mask firewalld  

Then, install the iptables-services package:

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yum install iptables-services  

Enable the service at boot-time:

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systemctl enable iptables  

Managing the service

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systemctl stop iptables  

systemctl start iptables  

systemctl |restart iptables  

Saving your firewall rules can be done as follows:

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service iptables save  

or

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/usr/libexec/iptables/iptables.init save  

参考文章：
http://www.centoscn.com/CentosBug/osbug/2014/0919/3779.html

http://www.cnblogs.com/love3556/p/5923392.html