Re: [chrony-users] Not getting time from gpsd

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I didn't think the -F option was correct but it didn't seem to work without it either.  I was just hunting and pecking.  My gps does not (directly) provide PPS.  It's a ublox 6 so I could probably wire it in but to be honest, I don't need that much precision.  For my needs NTP is accurate enough but it's not always available which is why I want time from GPS.  As for the dependencies and starting order, that's easy to fix.  Right now gpsd is starting from init.d and chrony is starting from systemd.  I can just remove the rc#.d links and write a new .service file for gpsd with "After = chrony.service" and "Wanted by =".  Then verify the chrony service file jives with the one for gpsd.

The last gps strace I posted was with the -D 8 option specified.   I did not, however, specify -f to strace so it is not following after it forks. 

As soon as I get some play time today I'll run some new traces.  Is attaching the best way to send the files or is there a bit bucket somewhere I should use?

On Aug 8, 2016 4:24 AM, "Miroslav Lichvar" <mlichvar@xxxxxxxxxx> wrote:
On Sun, Aug 07, 2016 at 10:27:02PM -0400, Chris Greenman wrote:
> I've attached the strace files.   The commands I used were:
> root@IrishMistII:/tmp# strace -o /tmp/chrony.strace.out chronyd
> root@IrishMistII:/tmp# strace -o /tmp/gpsd.strace.out gpsd -D 8 -F
> /var/run/chrony.ttyACM0.sock /dev/ttyACM0

The -F option of gpsd is for its control socket. It's not related to
the chrony socket. Also, I think gpsd uses the chrony socket only for
samples based on PPS signal, so if you don't have working PPS, you'll
probably need to stick with SHM.

The problem is most likely one of the following:
1) gpsd is not writing to SHM
2) chronyd is not reading from SMH
3) chronyd is ignoring SHM samples (e.g. when the receive timestamp is
   from future)

Output from "gpsd -D 8" should confirm it's not 1). For 2) and 3) it
would be best to see "chronyd -d -d" output, but this will work only
if chronyd was compiled with debugging support (configure has
--enable-debug option since chrony-1.30).

Recent gpsd releases include a ntpshmmon tool, which can print changes
in the SHM segment and could be useful to reject 1) and 2).

Miroslav Lichvar

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