[ntp:questions] Why does ntp keep changing my conf file?
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Sun Sep 19 05:08:16 UTC 2010
"David Woolley" <david at ex.djwhome.demon.invalid> wrote in message
news:i73bgf$ph$1 at news.eternal-september.org...
> David J Taylor wrote:
>> So, if I understand you correctly, you are saying that because ntp
>> measures and reports an offset, it will try and correct the clock in
>> the opposite direction, so that the actual clock error is likely to be
> So will ntpdate, but ntpdate only uses the most recent offset, whereas
> ntpd uses (to a first approximation) an exponential rolling average of
> the recent offsets, such that it makes effective use of quite a lot of
> them. That has a similar effect to using longer and longer averaging
> periods in MRTG. The time of the clock is much more accurate than any
> one offset would suggest.
> Complicating factors are that there is a non-linear finite impulse
> response filter (best of 8) ahead of the main, infinite impulse response
> one, the actual filter is not just solving for an offset, but also for
> the frequency, and the filter parameters are varied depending on an
> estimate of the quality of the time data.
I did say it was sometimes rather esoteric!
Is there any better parameter than offset= from an ntpq -c rv command
which one could plot?
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