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- Subject: [chrony-dev] chronyd not recovering after time stepped.
- From: Bryan Christianson <bryan@xxxxxxxxxxxxx>
- Date: Thu, 27 Aug 2015 22:20:45 +1200
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I had a problem with my principal NTP server the other day (different issue) but the result was a large jump in the offset on my Mac. This offset started to recover and then remained at around 70ms.
I can reproduce the problem by stepping the local clock while chronyd is running, using a small program that uses settimeofday() to advance the local clock.
For example:
I allow chronyd to run until fully in sync with NTP with sub 10usec offset
Step the local clock forward by 1500ms
chronyd reports an unexpected offset in the message log
chronyd[57399]: System clock wrong by -0.754267 seconds, adjustment started
chronyd starts correcting the offset and overshoots from -1000ms to around +70ms (as reported in tracking.log)
On close inspection, I can that the offset is dropping, but very, very slowly from 70ms to 50ms in an hour, i.e at about 5ppm. Maybe it will recover in a few hours?
Restarting chronyd clears the offset rapidly.
Is this normal behaviour?
I'm really not sure whats going on here and, if it is a problem, where I should be looking to debug it.
Regards
Bryan
--
Bryan Christianson
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