Re: [chrony-users] Synchronize system clock to GPS time

[Adrian Murphy <amurphy@xxxxxxxxxxxx>]

Hi Ryan,

Can I ask:

  You have ‘prefer’ option added to the 'server asdf.xyz’ line.

  Could that be stopping chronyd from trusting the GPS?

Also, asdf.xyz does resolve to an NTP server for me, but maybe you are hiding the real hostname.

On Ubuntu Raspberry Pi4 I use:

  refclock SOCK /run/chrony.pps0.sock refid PPS1 poll 5 prefer
  refclock SHM 0 refid GPS0 precision 1e-20 offset 0.036790 delay 0.0

  server Aeternitas iburst
  …

Also the end of your conf file was garbled. Is that real?

Cheers, Adrian


> On 4 Mar 2022, at 7:07 am, Ryan Govostes (he/him) <rgovostes@xxxxxxxx> wrote:
> 
> I have a GPS receiver with PPS connected to an embedded Linux system. GPSD feeds Chrony time updates from the GPS receiver over the Chrony socket.
> 
> The system clock is behind by a few months, and Chrony does not want to update the clock to the time reported by GPSD.
> 
> I have read the FAQ and a few threads on the same topic but the solutions presented don’t work for me. I have tried setting maxdistance to an absurdly high number, and allowing  makestep 1 -1.
> 
> The “chronyc sources” command suggests that Chrony thinks that the GPS is in error. There is no console message that says that Chrony is attempting to adjust the clock.
> 
> Can I force Chrony to accept the time from the GPS?
> 
> Thanks,
> Ryan
> 
> 
> $ chronyc sources
> 210 Number of sources = 3
> MS Name/IP address         Stratum Poll Reach LastRx Last sample               
> ===============================================================================
> #x GPS                           0   4   377    11   -2002h[ -2002h] +/-  100ms
> #x PPS                           0   4   377    10   -2002h[ -2002h] +/- 2919ns
> ^? asdf.xyz                      0   9     0     -     +0ns[   +0ns] +/-    0ns
> 
> $ chronyc tracking
> Reference ID    : 00000000 ()
> Stratum         : 0
> Ref time (UTC)  : Thu Jan 01 00:00:00 1970
> System time     : 0.000000041 seconds fast of NTP time
> Last offset     : +0.000000000 seconds
> RMS offset      : 0.000000000 seconds
> Frequency       : 404.716 ppm fast
> Residual freq   : +0.000 ppm
> Skew            : 0.000 ppm
> Root delay      : 1.000000000 seconds
> Root dispersion : 1.000000000 seconds
> Update interval : 0.0 seconds
> Leap status     : Not synchronised
> 
> $ cat /etc/chrony/chrony.conf 
> server asdf.xyz iburst prefer
> 
> # This directive specify the file into which chronyd will store the rate
> # information
> driftfile /var/lib/chrony/chrony.drift
> 
> # Log files location
> logdir /var/log/chrony
> 
> # Stop bad estimates upsetting machine clock
> #maxupdateskew 100.0
> 
> # This directive enables kernel synchronisation (every 11 minutes) of the
> # real-time clock
> rtcsync
> 
> # Step the system clock instead of slewing it if the adjustment is larger than
> # one second, but only in the first three clock updates
> makestep 1 -1
> 
> # 
> maxdistance 100000000
> 
> refclock SOCK /run/chrony.ttyCOM2.sock refid GPS precision 1e-1 offset 0.9999
> refclock SOCK /run/chrony.ppsCOM2.sock refid PPS precision 1e-7N‹§ēæėrļ›y隊W!Ū‰ōšĮŦē·Šđë-rčŸ+nÅöĶŠ\ĻŪ"ķ§ēæėrļ›z)í
> ë.n7œīZ+
> éizfĒ•ČkĒ|Ūąęė­ęŪzË\†š'ĘÛą}ĐĒ—*+ƒ­†ĨĶ)í
> ë.n7œĩ:čđđ^fĒ–XŽķfŽĩę܆š'ĘÛą}ĐĒ—*+


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