问题概述：
重启ntp服务报错Failed to restart ntpd.service: Unit is masked，使用systemctl unmask ntpd.service命令关闭屏蔽还是报错Failed to restart ntpd.service: Unit is masked
解决方法：
重装ntp服务
yum remove ntpyum install ntpsystemctl start ntpd.servicesystemctl enable ntpd.servicesystemctl status ntpd.service
