GEN000242 - The system must use at least two time sources for clock synchronization - 'cron jobs'


A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. For redundancy, two time sources are required so synchronization continues to function if one source fails. If the system is completely isolated (i.e., it has no connections to networks or other systems), time synchronization is not required as no correlation of events or operation of time-dependent protocols between systems will be necessary. If the system is completely isolated, this requirement is not applicable. Note: For the network time protocol (NTP), the requirement is two servers, but it is recommended to configure at least four distinct time servers which allow NTP to effectively exclude a time source not consistent with the others. The system's local clock must be excluded from the count of time sources.


If using 'ntpd -qg', add additional NTP servers to the cron job running 'ntpd -qg'.

If using the NTP daemon, add an additional 'server' line to /etc/ntp.conf for each additional NTP server.

See Also

Item Details


References: 800-53|AU-8(1), CAT|II, CCI|CCI-000160, Group-ID|V-22291, Rule-ID|SV-37412r1_rule, STIG-ID|GEN000242, Vuln-ID|V-22291

Plugin: Unix

Control ID: 9a2885d91bccae66607b1ed418a3c5bb90957de2a90abaff91e22d7baaee09dd