错误信息如下：
[root]# service iptables start
Redirecting to /bin/systemctl start iptables.service
Failed to start iptables.service: Unit iptables.service failed to load: No such file or directory.
解决方法如下：一直用CentOS 6 习惯了，一下没适应过来。防火墙配置后执行service iptables save 出现”Failed to restart iptables.service: Unit iptables.service failed to load: No such file or directory.”错误,
在CentOS 7或RHEL 7或Fedora中防火墙由firewalld来管理，当然你可以还原传统的管理方式。或则使用新的命令进行管理。
假如采用传统请执行一下命令：
systemctl stop firewalld
systemctl mask firewalld并且安装iptables-services：yum install iptables-services
设置开机启动：
systemctl enable iptablesiptables启动、关闭、保存：systemctl [stop|start|restart] iptables
#or
service iptables [stop|start|restart]service iptables save
#or
/usr/libexec/iptables/iptables.init save 
