[ntp:questions] NTPd looses sync regularly / 12 hour intervals.

Martin Burnicki martin.burnicki at meinberg.de
Wed Sep 8 15:25:36 UTC 2010


Michael,

Michael Nielsen wrote:
> The logs on the systems that have problems usually show the following
> pattern
> 
> 
> Sep  7 17:43:48 sn ntpd[11721]: synchronized to 10.7.100.28, stratum 2
> Sep  7 17:57:51 sn ntpd[11721]: time reset +71.784598 s
> Sep  7 17:59:10 sn ntpd[11721]: synchronized to 10.7.100.27, stratum 2
> Sep  8 05:29:11 sn ntpd[11721]: no servers reachable
> Sep  8 05:34:37 sn ntpd[11721]: synchronized to 10.7.100.28, stratum 2
> Sep  8 05:35:52 sn ntpd[11721]: time reset +74.977115 s
> Sep  8 05:36:41 sn ntpd[11721]: synchronized to 10.7.100.28, stratum 2

This looks like some other program is called in cyclic intervals (~12 hours,
run by cron?) to simply set the time to match the time of some external
time source.

After this has happened the offset and jitter figures reported by "ntpq -p"
should increase drastically, and about 15 minutes (or a certain number of
polling intervals) after the system time has been stepped by the other
program the time is stepped back by ntpd, causing the "time reset"
messages.

If the reference time source used by the other program continuously drifts
apart from the reference time source(s) used by ntpd then you should see
the amount of time reported by the "time reset"s increase or decrease
continuously.

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany




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