Re: [chrony-users] Fallback clock on event "Can't synchronise: no reachable sources"

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On Tue, 18 Feb 2014, Ulrich Schwesinger wrote:
The system waits for a poll interval before polling. If you poll interval is 10, that is 20 min. (approx) 



Hi,
I finally could get the tracking logs from the computer with one of the events in there, where the server is not reachable. Would be great if someone could help me interpret them. What I find strange is that there are large time intervals without an entry in the tracking.log file ... what does that mean? Is there something that looks suspicious? 

What looks suspicious is your source 192.168.0.30. What is that? Is it  going
mad.

Also your PPS/GPS? source seems to be having trouble getting locks.

I know on one of my Sure GPS devices the antenna was crap, and would flake out
for long periods of time, giving no signal. Is something similar happening to
you?

The measurements logs and the refclock log would also have been helpful




Thanks a lot, I appreciate the help!

Ulrich

tracking.log:
2014-02-17 11:09:38 192.168.0.30 14 -188.815 0.128 -2.652e-06 N 1 1.041e-05 -1.000e-06 2014-02-17 11:10:42 192.168.0.30 14 -188.825 0.105 -5.002e-06 N 1 9.495e-06 1.000e-06 
==================================================================================================
Date (UTC) Time IP Address St Freq ppm Skew ppm Offset L Co Offset sd Rem. corr. 
==================================================================================================
2014-02-17 11:14:47 0.0.0.0 0 -188.825 0.105 0.000e+00 ? 0 0.000e+00 0.000e+00 2014-02-17 11:20:06 192.168.0.30 14 -188.825 0.105 4.646e-01 N 1 8.165e-06 0.000e+00 2014-02-17 11:20:38 192.168.0.30 14 -188.825 0.105 -2.960e-02 N 1 7.342e-03 -4.700e-05 2014-02-17 11:21:10 192.168.0.30 14 -188.825 0.105 -1.061e-02 N 1 8.911e-03 3.000e-06 
==================================================================================================
Date (UTC) Time IP Address St Freq ppm Skew ppm Offset L Co Offset sd Rem. corr. 
==================================================================================================
2014-02-17 11:22:27 0.0.0.0 0 -188.825 0.105 0.000e+00 ? 0 0.000e+00 0.000e+00 2014-02-17 11:22:34 192.168.0.30 14 -188.825 0.105 -7.041e-03 N 1 7.408e-03 -1.356e-01 2014-02-17 11:22:36 192.168.0.30 14 -188.825 0.105 -1.281e-02 N 1 3.420e-03 -7.234e-02 2014-02-17 11:23:09 192.168.0.30 14 -188.825 0.105 -1.038e-02 N 1 1.155e-04 -4.000e-06 2014-02-17 11:23:41 192.168.0.30 14 -188.825 0.118 1.650e-04 N 1 1.582e-04 1.000e-06 2014-02-17 11:24:13 192.168.0.30 14 -188.825 0.141 4.837e-05 N 1 1.365e-04 -2.000e-06 2014-02-17 11:24:46 192.168.0.30 14 -188.824 0.191 6.054e-05 N 1 1.155e-04 -1.800e-05 2014-02-17 11:25:18 192.168.0.30 14 -188.820 0.296 4.109e-05 N 1 9.687e-05 -1.000e-05 2014-02-17 11:25:50 192.168.0.30 14 -188.792 0.584 7.567e-05 N 1 7.849e-05 -6.000e-06 
==================================================================================================
Date (UTC) Time IP Address St Freq ppm Skew ppm Offset L Co Offset sd Rem. corr. 
==================================================================================================
2014-02-17 11:27:07 0.0.0.0 0 -188.825 0.105 0.000e+00 ? 0 0.000e+00 0.000e+00 2014-02-17 12:43:35 192.168.0.30 14 -188.821 0.912 4.336e-01 N 1 1.704e-06 0.000e+00 2014-02-17 12:44:07 192.168.0.30 14 -188.821 0.912 -7.320e-04 N 1 8.288e-03 -4.400e-05 2014-02-17 12:44:40 192.168.0.30 14 -188.821 0.912 -7.830e-03 N 1 9.486e-03 5.310e-04 2014-02-17 12:45:12 192.168.0.30 14 -188.821 0.912 -4.389e-03 N 1 9.422e-03 1.060e-03 2014-02-17 12:45:45 192.168.0.30 14 -188.821 0.912 6.342e-04 N 1 8.040e-03 6.480e-04 2014-02-17 12:46:17 192.168.0.30 14 -188.821 0.912 3.129e-03 N 1 6.983e-03 1.300e-05 


statistics.log:
2014-02-17 11:09:38 192.168.0.30 1.751e-05 -2.652e-06 1.041e-05 -4.848e-09 1.200e-07 4.5e-02 15 0 9 2014-02-17 11:10:42 192.168.0.30 1.708e-05 -5.002e-06 9.495e-06 -1.166e-08 9.607e-08 9.1e-02 16 0 9 
==============================================================================================================
Date (UTC) Time IP Address Std dev'n Est offset Offset sd Diff freq Est skew Stress Ns Bs Nr 
==============================================================================================================
2014-02-17 11:20:06 192.168.0.30 1.246e-05 4.646e-01 8.165e-06 2.219e-06 1.972e-04 1.1e-03 3 0 3 2014-02-17 11:20:38 192.168.0.30 1.218e-02 -2.960e-02 7.342e-03 -4.316e-04 6.069e-03 2.2e+00 4 0 3 2014-02-17 11:21:10 192.168.0.30 1.131e-02 -1.061e-02 8.911e-03 -3.883e-04 1.876e-03 7.1e-03 5 0 4 
==============================================================================================================
Date (UTC) Time IP Address Std dev'n Est offset Offset sd Diff freq Est skew Stress Ns Bs Nr 
==============================================================================================================
2014-02-17 11:22:34 192.168.0.30 1.128e-02 -7.035e-03 7.408e-03 -4.449e-03 3.047e+00 2.2e+00 3 0 3 2014-02-17 11:22:36 192.168.0.30 5.950e-03 -1.281e-02 3.420e-03 -5.375e-03 5.774e-02 3.0e-04 4 0 3 2014-02-17 11:23:09 192.168.0.30 2.581e-04 -1.038e-02 1.155e-04 -4.700e-04 2.011e-03 8.5e-02 5 0 3 2014-02-17 11:23:41 192.168.0.30 3.054e-04 1.650e-04 1.582e-04 4.645e-06 6.898e-05 2.4e-01 6 0 3 2014-02-17 11:24:13 192.168.0.30 2.378e-04 4.837e-05 1.365e-04 2.609e-06 2.497e-05 3.0e-02 7 0 4 2014-02-17 11:24:46 192.168.0.30 1.989e-04 6.054e-05 1.155e-04 2.262e-06 1.223e-05 1.4e-02 8 0 4 2014-02-17 11:25:18 192.168.0.30 1.728e-04 4.109e-05 9.687e-05 1.919e-06 7.081e-06 2.8e-02 9 0 4 2014-02-17 11:25:50 192.168.0.30 1.505e-04 7.567e-05 7.849e-05 2.041e-06 4.414e-06 1.8e-02 10 0 5 
==============================================================================================================
Date (UTC) Time IP Address Std dev'n Est offset Offset sd Diff freq Est skew Stress Ns Bs Nr 
==============================================================================================================
2014-02-17 12:43:35 192.168.0.30 2.542e-06 4.336e-01 1.704e-06 1.581e-04 3.583e-05 7.9e-02 3 0 3 2014-02-17 12:44:07 192.168.0.30 8.349e-03 -7.320e-04 8.288e-03 7.286e-05 4.410e-03 2.4e+00 4 0 3 2014-02-17 12:44:40 192.168.0.30 9.411e-03 -7.830e-03 9.486e-03 -3.330e-05 1.436e-03 2.4e-02 5 0 3 2014-02-17 12:45:12 192.168.0.30 9.003e-03 -4.389e-03 9.422e-03 -5.436e-05 7.140e-04 1.5e-02 6 0 3 2014-02-17 12:45:45 192.168.0.30 8.527e-03 6.342e-04 8.040e-03 -3.774e-05 3.979e-04 2.3e-02 7 0 4 2014-02-17 12:46:17 192.168.0.30 8.356e-03 3.129e-03 6.983e-03 -1.324e-05 2.566e-04 6.2e-02 8 0 4 

On 07.02.2014 15:37, Miroslav Lichvar wrote:

 On Fri, Feb 07, 2014 at 02:10:32PM +0100, Ulrich Schwesinger wrote:
>  I have a system with a write protected system partition and an NTP
>  server running within a local network. Sporadically, chrony reports
>  the above mentioned error.
>  The error persists maybe within a time range of 20-30 seconds.
>  Within that time interval, the system time seems to diverge/drift by
>  a couple of 10 milliseconds, which seems unreasonable large for me.
 How did you measure the error in that period?

>  (a) What is chrony exactly doing upon the event "Can't synchronise:
>  no reachable sources". It does not seem to keep the current system
>  time. Is it falling back on hardware clock maybe?
 No, nothing with RTC. It should keep the system clock as it was set on
 the last update unless chronyd is configured with the fallbackdrift
 option.

>  (b) Or might something be wrong with the drift estimate, causing
>  this large divergence during the short time interval
 Did it switch to another source before the "no reachable sources"
 message? If there are multiple sources and the worst source becomes
 unreachable as last, the clock will be set by the measurement from the
 worst source, possibly introducing a large time or frequency error.

>  (c) Are there some files I could look at the trace back what's
>  happening within these time intervals?
 The tracking log would be very helpful here. You can enable logging
 in chrony.conf like this:

 logdir /var/log/chrony
 log measurements statistics tracking
I did not realise that you were using a refclock. Also log the refclock 









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