| Re: [chrony-users] chrony not demoting broken PPS source |
[ Thread Index |
Date Index
| More chrony.tuxfamily.org/chrony-users Archives
]
- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] chrony not demoting broken PPS source
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Wed, 9 Sep 2020 12:10:18 +0200
- Authentication-results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlichvar@xxxxxxxxxx
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599646226; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=LJoDKgf7sGSVTUi3nRRTjB4sdXM98AGLTt7LUczIDvs=; b=Leiup5ioaUysMZQ01n+sCOshV+PEAEJiU/o8qujUjYjq1A53flo0itb5WQaa/AspLAAlq2 SqYRlgAWUcqC2NdrmYceQN3ln4OzOSNJKyMMML17eeVyiyBWvA0AHvJKLQu3apj8QvhdNx 0sssZ660sfwPWwcOlJ+xBrsL5psSm1o=
On Wed, Sep 09, 2020 at 10:55:41AM +0100, Chris Spencer wrote:
> Hi,
>
> I have come across some slightly odd behaviour from chrony. We have a
> GPS time source with PPS. The device is currently indoors so the PPS
> is dropping in and out, but NMEA timestamps are still coming through.
> For some reason, chrony is still trying to use the broken PPS source
> even though it's not providing any data:
>
> # chronyc sources
> 210 Number of sources = 6
> MS Name/IP address Stratum Poll Reach LastRx Last sample
> ===============================================================================
> #- NMEA 0 4 377 11 -77ms[ -77ms] +/- 100ms
> #* GPS 0 4 0 101m +2315ns[+3536ns] +/- 141ns
> ^- time.cloudflare.com 3 6 377 100 -1167us[-1167us] +/- 64ms
> ^- ntp1.unix-solutions.be 2 6 136 359 -62us[ -62us] +/- 53ms
> ^- ntp.devrandom.be 2 6 377 100 +352us[ +352us] +/- 24ms
> ^- ntp2.unix-solutions.be 2 6 324 24m -150us[ -150us] +/- 30ms
The GPS time is much more accurate than the other time sources, so
it may take a long time before chronyd decides it should switch to
something else when it stops providing samples. It tries to minimize
the error of the clock taking into account its estimated stability.
You can speed up the reselection by increasing the maxclockerror
value.
> # cat /etc/chrony.conf
> refclock SHM 0 offset 0.155 delay 0.2 refid NMEA
The SHM refclock should have the noselect option if it's used only for
locking the PPS. If the GPS has no fix, the NMEA time will probably
drift away.
--
Miroslav Lichvar
--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "help" in the subject.
Trouble? Email listmaster@xxxxxxxxxxxxxxxxxxxx.