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Re[2]: NTP with only GPS/PPS flags PPS as falseticker

From: Nick Burkitt
Subject: Re[2]: NTP with only GPS/PPS flags PPS as falseticker
Date: Thu, 19 Mar 2020 03:48:44 +0000
User-agent: eM_Client/7.2.37929.0
Hi Gary.

And yet, not trying the things people suggest. Like chronyd, etc.
On the contrary. I've tried nearly everything that's been suggested. Changing to chronyd carries more risk than trying to learn what's happening with ntpd. If the current investigation comes up empty, that assessment may change.
 
Then you should have said "know", not "Thinking". We many drive-by's
here, and people changing things without saying anything. So
always good to restate your current configuration.
I know that there's nothing wrong with my use of the kernel PPSAPI. Beyond that I could have made any number of mistakes that ppstest can't detect. I was cured of false confidence a couple of decades ago.
 
root@MPM-4006:~# ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1584581522.999957214, sequence: 977 - clear
0.000000000, sequence:
Thar sure looks like your gpsd/ntpd is working. Less than 50 micro
second offset. Only PPS (or PTP) give you that.
Yes, which is why I haven't yet given up on ntpd. 

Yes, as previously discussed. But the result above is VERY different
from your previous reports.
Yes, promising, but not confidence inspiring.

> have you tried to set minsane?
Yes, here's my ntp.conf. We've been here before, too.
 
minsane 1
 
No. You never showed that. Good thing you did, as that is wrong.
Sorry - my mistake.
That should be throwing errors in the logs you have not shown us.
But there was no error message in the log. What happens if you duplicate my error? What gets logged?
The log excerpt I included had every non-DNS line issued by ntpd from the time it was restarted. The immediately-preceding line was ntpd announcing that it was exiting. 
 
The correct line is::
 
tos minsane 1
I'll restart again with the correct syntax and include the log beginning with  the shutdown line, for completeness.

The corrected ntp.conf:

tos minsane 1
refclock shm unit 2 refid PPS minpoll 3 maxpoll 3 prefer flag4 1
server 0.us.pool.ntp.org iburst
server 1.us.pool.ntp.org iburst
server 2.us.pool.ntp.org iburst
server 3.us.pool.ntp.org iburst
refclock shm unit 0 refid GPS minpoll 3 maxpoll 4 time1 0.080 flag4 1
restrict default kod limited nomodify nopeer noquery
restrict -6 default kod limited nomodify nopeer noquery
restrict 127.0.0.1
restrict -6 ::1
driftfile /var/lib/ntp/ntp.drift
statsdir /var/log/ntpstats/
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
logfile /var/log/ntpd.log
logconfig =syncall +clockall +peerall +sysall

ntpmon:
     remote           refid      st t when poll reach   delay   offset   jitter
xSHM(2)          .PPS.            0 l    3    8  377      0ns 28.997us 29.992us
 0.us.pool.ntp.o .DNS.           16 u    -    8    0      0ns      0ns  1.907us
 1.us.pool.ntp.o .DNS.           16 u    -    8    0      0ns      0ns  1.907us
 2.us.pool.ntp.o .DNS.           16 u    -    8    0      0ns      0ns  1.907us
 3.us.pool.ntp.o .DNS.           16 u    -    8    0      0ns      0ns  1.907us
xSHM(0)          .GPS.            0 l    6    8  377      0ns -8.072ms 2.9188ms
 pool.ntp.org    .POOL.          16 p    -    8    0      0ns      0ns  1.907us
ntpd ntpsec-1.1.8+ 2020-03-04T20:55:58Z        Updated: 2020-03-19T02:49:07 (4)
 lstint avgint rstr r m v  count rport remote address
      0   1.57    0 . 6 2    263 58970 localhost

command lines:
root@MPM-4006:/etc/ntp.d# ps -ef|egrep '(ntp|gps)'|grep -v grep
nobody    9609     1  0 01:15 ?        00:00:27 /usr/local/sbin/gpsd -n /dev/core100/gnss /dev/pps0
ntp      19607     1  0 02:39 ?        00:00:05 /usr/local/sbin/ntpd -D 10 -g -N -u ntp:ntp

ntpd.log:
I've started from the last line emitted by the previous incarnation of ntpd. I've run it through "grep -v DNS:". If you want to see the unadulterated version, I'll have to upload it somewhere. No one will want that in their email.

2020-03-19T02:39:10 ntpd[12274]: ERR: ntpd exiting on signal 15 (Terminated)
2020-03-19T02:39:10 ntpd[12274]: PROTO: SHM(2) 9612 82 demobilize assoc 43954
2020-03-19T02:39:10 ntpd[12274]: PROTO: 127.127.28.2 unlink local addr 127.0.0.1 -> <null>
2020-03-19T02:39:10 ntpd[12274]: PROTO: 0.0.0.0 8012 82 demobilize assoc 43955
2020-03-19T02:39:10 ntpd[12274]: PROTO: 0.0.0.0 8012 82 demobilize assoc 43956
2020-03-19T02:39:10 ntpd[12274]: PROTO: 0.0.0.0 8012 82 demobilize assoc 43957
2020-03-19T02:39:10 ntpd[12274]: PROTO: 0.0.0.0 8012 82 demobilize assoc 43958
2020-03-19T02:39:10 ntpd[12274]: PROTO: SHM(0) 9412 82 demobilize assoc 43959
2020-03-19T02:39:10 ntpd[12274]: PROTO: 127.127.28.0 unlink local addr 127.0.0.1 -> <null>
2020-03-19T02:39:10 ntpd[12274]: PROTO: 0.0.0.0 8812 82 demobilize assoc 43960
2020-03-19T02:39:10 ntpd[12274]: PROTO: 0.0.0.0 001d 0d kern kernel time sync disabled
2020-03-19T02:39:11 ntpd[19607]: INIT: Using SO_TIMESTAMPNS
2020-03-19T02:39:11 ntpd[19607]: IO: Listen and drop on 0 v6wildcard [::]:123
2020-03-19T02:39:11 ntpd[19607]: IO: Listen and drop on 1 v4wildcard 0.0.0.0:123
2020-03-19T02:39:11 ntpd[19607]: IO: Listen normally on 2 lo 127.0.0.1:123
2020-03-19T02:39:11 ntpd[19607]: IO: Listen normally on 3 lo [::1]:123
2020-03-19T02:39:11 ntpd[19607]: IO: Listening on routing socket on fd #20 for interface updates
2020-03-19T02:39:11 ntpd[19607]: PROTO: 127.127.28.2 8011 81 mobilize assoc 21309
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 8011 81 mobilize assoc 21310
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 8011 81 mobilize assoc 21311
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 8011 81 mobilize assoc 21312
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 8011 81 mobilize assoc 21313
2020-03-19T02:39:11 ntpd[19607]: PROTO: 127.127.28.0 8011 81 mobilize assoc 21314
2020-03-19T02:39:11 ntpd[19607]: CONFIG: configpeers: Ignoring duplicate '127.127.28.2'
2020-03-19T02:39:11 ntpd[19607]: CONFIG: configpeers: Ignoring duplicate '127.127.28.0'
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 8811 81 mobilize assoc 21315
2020-03-19T02:39:11 ntpd[19607]: SYNC: Found 10 servers, suggest minsane at least 3
2020-03-19T02:39:11 ntpd[19607]: INIT: This system has a 32-bit time_t.
2020-03-19T02:39:11 ntpd[19607]: INIT: This ntpd will fail on 2038-01-19T03:14:07Z.
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 c01d 0d kern kernel time sync enabled
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 c012 02 freq_set kernel 7.502304 PPM
2020-03-19T02:39:11 ntpd[19607]: PROTO: 0.0.0.0 c016 06 restart
2020-03-19T02:39:11 ntpd[19607]: INIT: OpenSSL 1.1.0g 2 Nov 2017, 1010007f
2020-03-19T02:39:11 ntpd[19607]: NTSc: Using system default root certificates.
2020-03-19T02:39:12 ntpd[19607]: PROTO: SHM(2) 8014 84 reachable
2020-03-19T02:39:12 ntpd[19607]: PROTO: SHM(2) 901a 8a sys_peer
2020-03-19T02:39:12 ntpd[19607]: PROTO: 0.0.0.0 c415 05 clock_sync
2020-03-19T02:39:17 ntpd[19607]: PROTO: SHM(0) 8014 84 reachable
2020-03-19T02:39:17 ntpd[19607]: PROTO: 0.0.0.0 0418 08 no_sys_peer
2020-03-19T02:39:49 ntpd[19607]: PROTO: SHM(2) 912a 8a sys_peer
2020-03-19T02:40:05 ntpd[19607]: PROTO: 0.0.0.0 0428 08 no_sys_peer
2020-03-19T02:40:13 ntpd[19607]: PROTO: SHM(2) 913a 8a sys_peer
2020-03-19T02:40:21 ntpd[19607]: PROTO: 0.0.0.0 0438 08 no_sys_peer
2020-03-19T02:40:32 ntpd[19607]: PROTO: SHM(2) 914a 8a sys_peer
2020-03-19T02:40:37 ntpd[19607]: PROTO: 0.0.0.0 0448 08 no_sys_peer
2020-03-19T02:41:41 ntpd[19607]: PROTO: SHM(2) 915a 8a sys_peer

 
And I've complained about the iburst before. As well as using the pool.
That won't affect the GPS issues. One thing at a time.

Gack. The interesting part is at the top, not the tail!!
 
So, once again, what do your ntpd logs show??
See above.

Thanks,

-Nick
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