| Re: [chrony-users] Strange "loss of PPS lock" |
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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] Strange "loss of PPS lock"
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Wed, 18 Jan 2023 14:41:28 +0100
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On Wed, Jan 18, 2023 at 02:14:26PM +0100, Rob Janssen wrote:
> refclock PPS /dev/pps0 refid PPS prefer
>
> and a couple (3-4) external NTP servers as absolute time reference.
> What can be the cause of this? The jitter value displayed in chronyc sources
> remains within 5-20us all the time. But the offset to PPS can go as high as 2ms
> during this. It may be that the combined offsets of the NTP servers as seen by
> chrony are closer to another than the PPS source is, but still I don't want them to
> get selected as long as the PPS can be locked and tracked.
chronyd doesn't cluster sources by their offset. If the PPS source is
marked as x, it doesn't agree with the NTP soures. Are those NTP
sources close in term of root distance? You could use the trust option
to force the selection of the PPS source if you are sure it's correct
and those NTP servers are wrong, but I think it's more likely your PPS
refclock is drifting for some reason, e.g. lost GPS signal. You could
specify a delay of few milliseconds with delay option to ensure an
overlap with the NTP soures.
--
Miroslav Lichvar
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