[ntp:questions] Clock skew changes drastically between reboots
devnull at localhost.com
Tue Apr 3 07:29:39 UTC 2007
Ronan Flood wrote:
> Spoon wrote:
>> I rebooted the computer at 10:38:26
>> I removed the drift file and started ntpd.
> Why did you remove the drift file? It is there to provide some
> state when restarting ntpd.
On these systems, after a reboot, the value in the drift file is
completely wrong. Letting ntpd think that it is an appropriate
approximation slows down the computation of the new frequency offset.
I followed Professor Mills's methodology.
1. Run ntptime -f 0 to remove any leftover kernel bias.
2. Configure for a reliable server over a quiet network link.
3. Remove the frequency file ntp.drift.
4. Start the daemon and wait for at least 15 minutes until ntpq -c
rv shows state=4. Record the frequency offset. It should be within 1 PPM
of the actual frequency offset. For enhanced confidence, wait until the
first frequency file update after one hour or so.
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