### Install NTPd.
[root@testos ~]# yum -y install ntp
### Edit/Update NTP Configuration file
[root@testos ~]# vi /etc/ntp.conf
### line 18: add the network range you allow to receive requests
restrict 10.0.0.0 mask 255.255.255.0 nomodify notrap
### change servers for synchronization
### change servers for synchronization #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 server <NTP1 SERVER ADDRESS> iburst server <NTP2 SERVER ADDRESS> iburst server <NTP3 SERVER ADDRESS> iburst
### Start&Enable NTPD service
[root@testos ~]# systemctl start ntpd
[root@testos ~]# systemctl enable ntpd
### If Firewalld is running, allow NTP service. NTP uses 123/UDP.
[root@testos ~]# firewall-cmd –add-service=ntp –permanent
success
[root@testos ~]# firewall-cmd –reload
success
### Verify & Check NTP
[root@testos ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+ntp1.ntp.test. 10.229.20.120 2 u 29 64 1 18.826 -0.126 0.000
+ntp2.ntp.test. 10.210.10.55 2 u 28 64 1 21.592 0.018 0.000
*ntp3.ntp.test. 10.133.20.20 2 u 28 64 1 22.666 -1.033 0.000