NTPd : NTP Server installation on centos7

1. NTP package is provided by default from Centos  repositories, and can be installed by the following command:

[root@Centos7 ~]# yum -y install ntp

2. Configure these lines.

[root@Centos7 ~]# vi /etc/ntp.conf
# line 18: add the network range you allow to receive requests
restrict 172.160.0.0 mask 255.255.0.0 nomodify notrap

# 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.example.local iburst
server ntp2.example.local iburst

3. Once the installation completes, start the service and configure it so it starts automatically each time the server boots:

[root@Centos7 ~]# systemctl start ntpd
[root@Centos7 ~]# systemctl enable ntpd

4. Add the NTP service in firewall

[root@Centos7 ~]# firewall-cmd --add-service=ntp --permanent
success
[root@Centos7 ~]# firewall-cmd --reload
success

5. To get a basic report you can use
[root@Centos7 ~]# ntpstat

[root@Centos7 ~]# date

6. To get some information about the time synchronization process

[root@Centos7 ]# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+172.16.66.237   162.23.41.10     2 u  811 1024  377  138.115   -5.214   6.138
*sin.wrtpoona.in 198.168.177.157  2 u  262 1024  377   45.978   -0.386   5.468
+greenore.zeip.e 140.203.204.77   2 u  175 1024  177  133.697    0.892   8.112
+mx.fimn.net     85.199.214.102   2 u  931 1024  377  128.804   -2.038   6.486