These instructions describe how to configure ntpd across the 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 ** mask ** nomodify notrap.
  3. Run firewall-cmd --permanent --add-service=ntp
  4. Run firewall-cmd --permanent --add-service=ntp --permanent
Assistant Professor

My research interests include free and open source software, system security, and network security.