Problem with GPSD refclock

Eric S. Raymond esr at
Thu Jan 26 03:27:16 UTC 2017

Rich Wales <richw at>:
> Hi.  I'm trying ntpsec-0.9.6+195 2017-01-18T11:59:53Z on an Ubuntu
> 16.04.1 LTS Server system with a GPS reference clock managed by gpsd.
> The following works just fine under ntpd 4.2.8p4 at 1.3265-o:
> server	mode 1 minpoll 3 maxpoll 6 prefer
> fudge	stratum 0 refid GPS
> But with ntpsec, when I replaced the above configuration lines with the
> following line --
> refclock gpsd prefer unit 0 mode 1 minpoll 3 maxpoll 6 stratum 0 refid GPS
> -- the reference clock seems to be silently ignored (no errors, but the
> refclock doesn't show up in "ntpq -c peers", and the server syncs to one
> of its peers instead of to the refclock).
> Is there something obvious I might be missing here in the configuration?
>  What can people recommend I try at this point to help determine what
> the problem is?

That looks like it ought to work, but my suspicion falls on the gpsd
refclock driver.  It has never worked really right; that's a problem
we inherited from Classic and are trying to fix.

We recomend using GPSD's SHM interface. (For this purpose you want to
run it as root.) These lines work for me:

# GPS Serial data reference (NTP0)
refclock shm unit 0 refid GPS

# GPS PPS reference (NTP1)
refclock shm unit 1 refid PPS

		<a href="">Eric S. Raymond</a>

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