rpm -q ntp -- 验证是否安装 ntp 服务
yum install -y ntp -- 群发，如果没有 ntp 服务则安装一个
systemctl enable ntpd
systemctl start ntpd
systemctl status ntpd
配置服务端
vim /etc/ntp.conf
restrict 127.0.0.1
restrict ::1
server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst
[root@153 ~]# ntpstat
synchronised to NTP server (202.118.1.81) at stratum 2
time correct to within 983 ms
polling server every 64 s
[root@153 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*time.neu.edu.cn .PTP. 1 u 16 64 1 61.155 14.381 7.256
sv1.ggsrv.de 192.53.103.103 2 u 15 64 1 241.410 18.393 0.197
111.230.189.174 100.122.36.196 2 u 14 64 1 21.831 16.980 0.174
time.neu.edu.cn .PTP. 1 u 13 64 1 59.822 15.195 0.231
客户端配置：
vim /etc/ntp.conf
restrict 127.0.0.1
restrict ::1
server *.*.*.* #指向serverIP
测试是否正常
[root@154 ~]# ntpstat
unsynchronised
time server re-starting
polling server every 8 s
[root@154 ~]# ntpstat
synchronised to NTP server (191.191.170.153) at stratum 12
time correct to within 1462 ms
polling server every 64 s
[root@dwzt154 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
t153 111.230.189.174 3 u 18 64 377 0.297 67.915 15.657
[root@dwzt154 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
153 LOCAL(0) 11 u 22 64 377 0.245 31.356 4.721
