RE: [chrony-users] reachability cycling between 377 to 000

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Subject: RE: [chrony-users] reachability cycling between 377 to 000
From: <wis1@xxxxxxxxxxx>
Date: Mon, 19 Oct 2020 17:42:17 -0700
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Title: RE: [chrony-users] reachability cycling between 377 to 000

>-----Original Message-----

>From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>

>Sent: Monday, October 19, 2020 12:15 AM

>To: chrony-users@xxxxxxxxxxxxxxxxxxxx

>Subject: Re: [chrony-users] reachability cycling between 377 to 000

>On Thu, Oct 15, 2020 at 05:50:01PM -0700, wis1@xxxxxxxxxxx wrote:

>> If I monitor the output from 'chronyc sources', I see the reachability

>> status change regularly from "377" to "000" and back again. Is this a

>> known problem or a wrong / incomplete configuration?

>Can you please post your chrony.conf and full chronyc sources? One

>possibility is that the PPS locking is not good. This could be due to an incorrect

>delay or offset specified for the NMEA source to which the PPS is trying to

>lock. Try it without the lock option and ideally also with some NTP servers.

The “chrony.conf” and the ‘chronyc sources’ output are shown below. Note

that the previous data had the non-PPS lines stripped out. The NTP pool

sources were present the whole time, but not shown in the earlier data.

You piqued my interest in the “chrony.conf” file, which I copied off some

web page purporting to explain how to get ‘chronyd’ working. Note the

“refclock PPS /dev/pps0 refid PPS lock GPS” line in “chrony.conf”.

My “ntp.conf” file (when running ‘ntpsec’), shows:

# GPS PPS reference (NTP1)

refclock shm unit 1 refid PPS

# GPS Serial data reference (NTP0)

refclock shm unit 0 refid GPS

When I changed “chrony.conf” to include

refclock SHM 1 poll 3 refid PPS lock GPS

Restarting ‘chronyd’ with this gives a solid 377 all the time (where “all

the time” is defined as “> 60 min and I got bored”). I’m now seeing:

wis@raspberrypi:~ $ chronyc sources

210 Number of sources = 6

MS Name/IP address Stratum Poll Reach LastRx Last sample

===============================================================================

#x GPS 0 3 377 6 +154ms[ +154ms] +/- 299us

#* PPS 0 3 377 6 -221ns[ -279ns] +/- 444ns

^- time-b.as43289.net 2 6 377 4 +30ms[ +30ms] +/- 214ms

^- ntpppool.uni-ruse.bg 2 8 377 140 -6142us[-6141us] +/- 147ms

^- ntp1.wtnet.de 2 8 377 143 +17ms[ +17ms] +/- 130ms

^- ntp13.kashra-server.com 2 8 367 138 -4534us[-4534us] +/- 106ms

wis@raspberrypi:~ $ chronyc tracking

Reference ID : 50505300 (PPS)

Stratum : 1

Ref time (UTC) : Tue Oct 20 00:24:30 2020

System time : 0.000000018 seconds slow of NTP time

Last offset : -0.000000016 seconds

RMS offset : 0.000000174 seconds

Frequency : 17.434 ppm fast

Residual freq : -0.000 ppm

Skew : 0.005 ppm

Root delay : 0.000000001 seconds

Root dispersion : 0.000010703 seconds

Update interval : 8.0 seconds

Leap status : Normal

This is much better. Are the PPS adjustments and uncertainty reasonable, or

do I have more tuning?

Thank you for the help.

-wis

*************************************************

Initial "chrony.conf”

*************************************************

pool pool.ntp.org iburst

refclock SHM 0 poll 3 refid GPS

refclock PPS /dev/pps0 refid PPS lock GPS

driftfile /var/lib/chrony/drift

makestep 10 3

- end -

*************************************************

'chrony sources' output on reachability changes

*************************************************

2020-10-19T22:25:14 377 -> 376 08:15 GGA lock: 1

#x GPS 0 3 377 4 +629ms[ +629ms] +/- 13ms

#* PPS 0 4 376 25 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 171 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 570 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 178 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 109 -2252us[-2252us] +/- 40ms

2020-10-19T22:25:30 376 -> 374 00:16 GGA lock: 1

#x GPS 0 3 377 5 +631ms[ +631ms] +/- 12ms

#* PPS 0 4 374 41 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 187 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 586 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 194 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 125 -2252us[-2252us] +/- 40ms

2020-10-19T22:25:46 374 -> 370 00:16 GGA lock: 1

#x GPS 0 3 377 4 +631ms[ +631ms] +/- 11ms

#* PPS 0 4 370 57 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 203 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 602 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 210 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 141 -2252us[-2252us] +/- 40ms

2020-10-19T22:26:02 370 -> 360 00:16 GGA lock: 1

#x GPS 0 3 377 5 +631ms[ +631ms] +/- 10ms

#* PPS 0 4 360 73 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 219 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 618 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 226 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 157 -2252us[-2252us] +/- 40ms

2020-10-19T22:26:18 360 -> 340 00:16 GGA lock: 1

#x GPS 0 3 377 5 +631ms[ +631ms] +/- 9693us

#* PPS 0 4 340 89 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 235 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 634 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 242 +885us[ +885us] +/- 36ms

^- tick.noc.unlv.edu 2 8 377 173 -2252us[-2252us] +/- 40ms

2020-10-19T22:26:34 340 -> 300 00:16 GGA lock: 1

#x GPS 0 3 377 5 +632ms[ +632ms] +/- 8976us

#* PPS 0 4 300 105 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 251 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 650 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 258 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 189 -2252us[-2252us] +/- 40ms

2020-10-19T22:26:50 300 -> 200 00:16 GGA lock: 1

#x GPS 0 3 377 4 +629ms[ +629ms] +/- 8312us

#* PPS 0 4 200 121 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 267 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 666 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 274 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 205 -2252us[-2252us] +/- 40ms

2020-10-19T22:27:06 200 -> 0 00:16 GGA lock: 1

#x GPS 0 3 377 4 +630ms[ +630ms] +/- 7700us

#* PPS 0 4 0 137 -172ns[ -211ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 9 377 283 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 682 -1146us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 290 +885us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 221 -2252us[-2252us] +/- 40ms

2020-10-19T22:38:02 0 -> 1 10:56 GGA lock: 1

#x GPS 0 3 377 4 +163ms[ +163ms] +/- 15ms

#* PPS 0 4 1 10 -487ns[-3063ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 939 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 22m -1147us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 946 +886us[ +885us] +/- 36ms

^- tick.nde.unlv.edu 2 8 377 619 -3236us[-3237us] +/- 45ms

2020-10-19T22:38:18 1 -> 3 00:16 GGA lock: 1

#x GPS 0 3 377 4 +163ms[ +163ms] +/- 14ms

#* PPS 0 4 3 5 -283ns[ -536ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 955 -1073us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 22m -1147us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 962 +885us[ +885us] +/- 36ms

^- tick.net.unlv.edu 2 8 377 635 -3236us[-3237us] +/- 45ms

2020-10-19T22:38:34 3 -> 7 00:16 GGA lock: 1

#x GPS 0 3 377 4 +163ms[ +163ms] +/- 13ms

#* PPS 0 4 7 8 -326ns[ -779ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 971 -1074us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 22m -1148us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 978 +885us[ +885us] +/- 36ms

^- tick.noc.unlv.edu 2 8 377 651 -3236us[-3237us] +/- 45ms

2020-10-19T22:38:50 7 -> 17 00:16 GGA lock: 1

#x GPS 0 3 377 4 +162ms[ +162ms] +/- 12ms

#* PPS 0 4 17 8 -222ns[ -304ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 987 -1074us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 23m -1148us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 994 +885us[ +885us] +/- 36ms

^- tick.noc.unlv.edu 2 8 377 667 -3236us[-3237us] +/- 45ms

2020-10-19T22:39:06 17 -> 37 00:16 GGA lock: 1

#x GPS 0 3 377 4 +162ms[ +162ms] +/- 11ms

#* PPS 0 4 37 8 -303ns[ -387ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 1003 -1074us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 23m -1148us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 1010 +885us[ +885us] +/- 36ms

^- tick.net.unlv.edu 2 8 377 683 -3236us[-3237us] +/- 45ms

2020-10-19T22:39:22 37 -> 77 00:16 GGA lock: 1

#x GPS 0 3 377 4 +161ms[ +161ms] +/- 10ms

#* PPS 0 4 77 8 +129ns[ +158ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 1019 -1074us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 23m -1148us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 1026 +885us[ +885us] +/- 36ms

^- tick.net.unlv.edu 2 8 377 699 -3236us[-3237us] +/- 45ms

2020-10-19T22:39:38 77 -> 177 00:16 GGA lock: 1

#x GPS 0 3 377 4 +162ms[ +162ms] +/- 9264us

#* PPS 0 4 177 9 +264ns[ +314ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 1035 -1074us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 23m -1148us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 1 +1881us[+1881us] +/- 35ms

^- tick.nde.unlv.edu 2 8 377 715 -3236us[-3237us] +/- 45ms

2020-10-19T22:39:54 177 -> 377 00:16 GGA lock: 1

#x GPS 0 3 377 3 +163ms[ +163ms] +/- 8579us

#* PPS 0 4 377 8 -421ns[ -492ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 1051 -1074us[-1073us] +/- 72ms

^- main.krajany.vn.ua 2 9 377 24m -1148us[-1147us] +/- 148ms

^- andromeda.cs.purdue.edu 1 10 377 17 +1881us[+1881us] +/- 35ms

^- tick.noc.unlv.edu 2 8 377 731 -3236us[-3237us] +/- 45ms

2020-10-19T22:50:50 377 -> 376 10:56 GGA lock: 1

#x GPS 0 3 377 5 +629ms[ +629ms] +/- 456us

#* PPS 0 4 376 24 +219ns[ +245ns] +/- 444ns

^- 50-205-57-38-static.hfc.> 2 10 377 145 +116us[ +115us] +/- 82ms

^- main.krajany.vn.ua 2 10 377 35 -2914us[-2914us] +/- 144ms

^- andromeda.cs.purdue.edu 1 10 377 673 +1881us[+1881us] +/- 35ms

^- tick.nde.unlv.edu 2 8 377 352 -2762us[-2762us] +/- 60ms

* end *******************************************

*************************************************

Versions

*************************************************

wis@raspberrypi:~ $ chronyd -v

chronyd (chrony) version 3.5.1 (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP -SCFILTER -SIGND +ASYNCDNS -SECHASH +IPV6 -DEBUG)

wis@raspberrypi:~ $ gpsd -Version

gpsd: 3.21.1~dev (revision release-3.21-191-ge80e4bd75)

wis@raspberrypi:~ $ uname -a

Linux raspberrypi 5.4.51-v7l+ #1333 SMP Mon Aug 10 16:51:40 BST 2020 armv7l GNU/Linux

*************************************************

Follow-Ups:
- Re: [chrony-users] reachability cycling between 377 to 000
  - From: Miroslav Lichvar

References:
- [chrony-users] reachability cycling between 377 to 000
  - From: wis1
- Re: [chrony-users] reachability cycling between 377 to 000
  - From: Miroslav Lichvar

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