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：
1、随便写一条iptables命令配置个防火墙规则：如：
iptables -P OUTPUT ACCEPT
2，进行保存
service iptables save
3，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 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:
Then,install the iptables-services package:
Enable the service at boot-time:
copy
