启动防火墙时出现：
Failed to restart iptables.service: Unit not found.
解决方案：
1.https://stackoverflow.com/questions/24756240/how-can-i-use-iptables-on-centos-7
Linux_异常_02_Failed to restart iptables.service: Unit not found.
原文：http://www.cnblogs.com/shirui/p/7999492.html