原因：在新安裝的Linux系統中，防火牆預設是被禁掉的，一般也沒有配置過任何防火牆的策略，所有不存在/etc/sysconfig/iptables檔案。

解決辦法：
1、隨便寫一條iptables命令配置個防火牆規則：如：

iptables -P OUTPUT ACCEPT

2，進行儲存

service iptables save

3，service iptables restart

異常

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.

With RHEL 7 / CentOS 7, 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:
 

systemctl stop firewalld
systemctl mask firewalld
 

yum install iptables-services

systemctl enable iptables

systemctl stop iptables

systemctl start iptables

systemctl |restart iptables

service iptables save

/usr/libexec/iptables/iptables.init save
 

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

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