NTP

These instructions describe how to configure ntpd across the 10.0.0.0/24 subnet so that one host, NTP.EXAMPLE.COM, acts as the subnet’s NTP server. We make use of ntpd instead of chrony.

On each host:

  1. rpm -e chrony.
  2. yum install ntp.
  3. Hosts other than NTP.EXAMPLE.COM should only permit NTP connections from localhost. In these cases, merely replace the server statements in /etc/ntp.conf with one that references your NTP server, NTP.EXAMPLE.COM.
  4. Start the ntpservice.

On NTP.EXAMPLE.COM, follow the steps above, except:

  1. Set server to point to the upstream NTP host.
  2. Set restrict *10.0.0.0* mask *255.255.255.0* nomodify notrap.
  3. Run firewall-cmd --permanent --add-service=ntp
  4. Run firewall-cmd --permanent --add-service=ntp --permanent