[chrony-users] How to set GPS and PPS source offline

["Wielant, Ulrich" <u.wielant@xxxxxxxxxxxxxxxxx>]

Hi,

I am a chrony (2.4.1) newbie but up to now I am very happy about the ease of use (compared to ntpd ;-).

Now I am facing a problem using a GPS as time source connected via gpsd.

Referring to the gpsd documentation I added the two lines:
refclock SHM 0 refid GPS precision 1e-1 offset 0.18 delay 0.2
refclock SOCK /var/run/chrony.ttyS0.sock refid PPS

Additionally I have some other servers configured:
server 0.de.pool.ntp.org iburst
server 1.de.pool.ntp.org iburst
server 2.de.pool.ntp.org iburst
server 3.de.pool.ntp.org iburst

Running chrony and gpsd the chrony synchronises to the GPS device.

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#- GPS                           0   4   377     8    +24ms[  +24ms] +/-  200ms
#* PPS                           0   4   377     4   +595ns[ +646ns] +/- 1481ns
^- ntp03.cc-netzwerk.de          3   8   377     4  -1791us[-1791us] +/-   31ms
^- ts1.sct.de                    2   8   377    13   -278us[ -278us] +/-   37ms
^- news01.nierle.com             2   8   377   199  -1351us[-1489us] +/-   42ms
^- xserv-01.tenretni.org         2   8   377     6  -4456us[-4456us] +/-   62ms

After chrony synchronized once to the PPS it never selects another time source although the PPS/GPS signal might disappear. This might be the case if gpsd is not running, the GPS is off or the GPS has no fix.

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#- GPS                           0   4     0   21m    +44ms[  +44ms] +/-  200ms
#* PPS                           0   4     0   21m  -1211ns[-2913ns] +/- 1634ns
^- ntp03.cc-netzwerk.de          3   8   377    47  -1809us[-1809us] +/-   42ms
^- ts1.sct.de                    2   8   377    55   -403us[ -403us] +/-   60ms
^- news01.nierle.com             2   8   377   246  -1518us[-1518us] +/-   38ms
^- xserv-01.tenretni.org         2   8   377    53  -4528us[-4528us] +/-   58ms

What do I have to do so that chrony no longer synchronizes to the non available PPS/GPS source?

I would also modify the stratum of the PPS/GPS source but this doesn't seem to be possible with refclock sources. Correct?

Thanks!
Ulrich

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