[ntp:questions] Re: HowTo calibrate system clock frequency using NTP

Daniel Kabs daniel.kabs at gmx.de
Mon Mar 20 16:29:30 UTC 2006


I think that one important step is missing:

David L. Mills wrote:
> Plan B
> 1. Run ntptime -f 0 to remove any leftover kernel bias.

Here one should also remove the frequency file "ntp.drift". Otherwise 
NTP daemon reads it and configures the kernel clock adjustment 
parameters. In this case one ends up measuring a residual frequency 
error as part of the frequency error has been compensated.

> 2. Configure for a reliable server over a quiet network link.
> 3. Start the daemon with disable ntp in the configuration file.
> 4. Record the offset over a period of hours. Do a least-squares fit; the 
> regression line slope is the frequency.

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