[ntp:questions] Very large offset and jitter values after reboot

David Woolley david at ex.djwhome.demon.co.uk.invalid
Mon Aug 25 15:22:10 UTC 2008

Richard B. Gilbert wrote:

> If the temperature of the machine has changed significantly since the 
> drift file was written, ntpd will start with an incorrect value for 
> drift.  If you are doing a cold start, it is usually best to delete the 
> drift file.  The drift file is overwritten with a new value every hour.

You would need a large temperature variation to justify this.  If the 
devices were exposed to the elements it might be justified. It would 
rarely be justified if they were in living space.

One consequence of deleting the file is that it forces a frequency 
calibration, which means that, once there are enough samples (about 6) 
to set the clock, it will be allowed to free run for about 15 minutes 
before having any further corrections applied.  If you want a tight lock 
in less than 20 minutes, you need a drift file.

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