[ntp:questions] Increase maximum frequency offset to deal with really bad clock

Richard B. Gilbert rgilbert88 at comcast.net
Wed Jan 28 22:19:57 UTC 2009


jeff at sailorfej.net wrote:
> Hi folks,
> 
> I have a some FreeBSD systems running as guests in Microsoft Virtual
> Server.  There is a known problem with these were the clocks run very
> fast.  I am trying to use ntpd to keep their clocks in sync, but the
> frequency error offset is exceeding (I think) ntpd's maximum of 500,
> my driftfile always contains a value of "-500.000".  If understand the
> way this works correctly, if I could get the frequency error offset to
> represent the real error rate which I believe to be much higher that
> 500 PPM, then ntpd would be able to keep the clocks in sync, as it is
> now, it slowly falls behind until it fails to correct altogether.
> 
> So is it possible to override the maximum offset PPM in the driftfile,
> or is there a better way to fix this?
> 
> Thanks,
> Jeff

I'm not familiar with BSD but if there is a way to reduce the speed at 
which the clock ticks, using it MIGHT bring the clock close enough that 
NTPD could discipline it.   The 500 PPM limits translate to +/- 43 
seconds per day so, if your clock is outside the limits it is REALLY 
off.  The cheapest wrist watches do better than that!!




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