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Re: Questions about GPSD as a time source with Chrony
From: |
Gary E. Miller |
Subject: |
Re: Questions about GPSD as a time source with Chrony |
Date: |
Tue, 5 Apr 2022 11:13:30 -0700 |
Yo Dominick!
On Mon, 4 Apr 2022 22:27:38 -0400
"Dominick C. Pastore" <dominickpastore@dcpx.org> wrote:
> >> refclock SHM 0 refid GPSH
> >> refclock SHM 1 refid PPSH
> >> refclock SOCK /var/run/chrony.gpsd0.sock refid GPSO
> >
> > The above 3 a godd.
>
> Pardon? (My best guess is that line was supposed to read, "The above
> 3 are good," but I don't want to assume.)
Yes, good.
> >> refclock SOCK /var/run/chrony.pps0.sock refid PPSO
> >
> > What said to do that? chonry.gpsd0.sock is obviously your PPS,
> > note the good 120 ns jitter. That is what you want. All done.
>
> The GPSD Time Service HOWTO did. Specifically, it said this:
>
> "To get chronyd to connect to gpsd using the socket method add the
> following lines your chrony.conf file. Except, replace XXXX with the
> basename of your device’s serial port, often ttyS0, ttyACM0, or
> ttyAMA0. Replace YYYY with the basename of your PPS device, usually
> pps0.
Yes, except when you have the MAGIC_HAT option on, as you do. The
doc needs to be clearer.
> > So you have both SHM and the socket file working. I don't see any
> > problems.
>
> Then I don't have any problems, but it seems the GPSD Time Service
> HOWTO might. It sounds like the suggested configuration for the
> socket method is incorrect, unless I am misunderstanding something.
It is incorrect for your configuration, but correct for most
configurations.
> >> The GPSD Time Service HOWTO seems to suggest using the socket
> >> interface for Chrony over the shared memory interface.
> >
> > Yes.
> >
> >> Is there some
> >> advantage to the socket interface?
> >
> > No. Just the opposite.
>
> If by "just the opposite" you mean there is a disadvantage to the
> socket interface (as opposed to merely no advantage),
Correct.
> that begs the
> questions: 1) Why is the SHM interface better,
It is more general (works with ntpd and chrinyd). It avoids the
stupid effects of SELinux, AppArmore, etc. It avoids file permission
problems.
> and 2) should the
> HOWTO reflect that reality?
No, too much details turns off readers.
> I appreciate the responses.
Be sure to pass on your knowledge to the next newbie.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can't measure it, you can't improve it." - Lord Kelvin
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