Thank you, [email protected], for your response to my question. Couple follow-up questions. My ntp.conf running on Linux has 4 servers defined:
server 0.rhel.pool.ntp.org server 1.rhel.pool.ntp.org server 2.rhel.pool.ntp.org These are public servers from the NTP pool project. In my /var/log/diag-log file, I see messages indicating that my ntpd is synching with individual servers, for example: Aug 7 09:53:58 yellowstone ntpd[3272]: synchronized to 69.50.219.51, stratum 2 Aug 7 10:04:52 yellowstone ntpd[3272]: synchronized to 184.82.112.110, stratum 2 Aug 7 10:39:05 yellowstone ntpd[3272]: synchronized to 69.50.219.51, stratum 2 Aug 7 11:28:17 yellowstone ntpd[3272]: synchronized to 184.82.112.110, stratum 2 Aug 7 12:47:06 yellowstone ntpd[3272]: synchronized to 128.10.19.24, stratum 1 ... Aug 8 11:37:43 yellowstone ntpd[3254]: synchronized to 50.116.55.65, stratum 2 Aug 8 12:18:46 yellowstone ntpd[3254]: synchronized to 50.116.55.161, stratum 2 Aug 8 13:01:27 yellowstone ntpd[3254]: synchronized to 38.101.77.21, stratum 2 Aug 8 15:01:00 yellowstone ntpd[3254]: synchronized to 50.116.55.161, stratum 2 Aug 8 16:09:20 yellowstone ntpd[3254]: synchronized to 38.101.77.21, stratum 2 These log messages suggest that ntpd is synchronizing with one and only one NTP server. Is that the correct interpretation? Is this single server selected for synchronization only after performing all the calculations described below? Also, I see long time periods in the diag-log where there is no synchronization message. What does that signify? No agreement between the servers on the correct time? No need to adjust system clock because it is already in sync? Thanks, Nils Brubaker On 2013-08-13, Nils Brubaker <ncb at us.ibm.com> wrote: > For ntpd 4.2.4p6 running on Linux, is there any significance to the order > of servers in the ntp.conf file? Will ntpd synchronize with the first > available/good time server in the list? No, no. ntp gets the data from all the servers. It then looks at the times it gets from each server, and groups them into "classes" according to its estimate of the max time error from the server-- ie whether the error intervals overlap or not. It then looks for the largest group of servers all of whose error intervals overlap and uses the average of those times as the time to send on the the ntp engine. The others are "false tickers". It estimates the error by looking at the round trip time and the other machine's estimate of its own max error. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
