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

[Nick Burkitt]

Hi Martin.

Have you tried disconnecting from any networks to see what happens to GPS and PPS?

Lowering the priority of the GPS clock source isn't the issue - I've done that by putting it last in my ntp.conf file. The problem is that ntpd won't use it at all, and when it (ntpd) has no clock sources left, it won't use PPS, either. 

-Nick

------ Original Message ------

From: "Residual Catch-all" <address@hidden>

To: "Nick Burkitt" <address@hidden>

Sent: 3/14/2020 3:44:50 PM

Subject: Re: NTP with only GPS/PPS flags PPS as falseticker

Hi!

In my ntp.conf, I set the GPS time source (SHM0 for you) to stratum 11. NTP would use anything but that if it has a choice. If it doesn't, it's there to serve. 

It also makes the line's position in the file less relevant I believe. Right?

Martin Boissonneault

Sent from my phone

On Mar 14, 2020, at 18:38, Nick Burkitt <address@hidden> wrote:



Hi Gary.

I need to tweak my ntpd.conf so that ntpd will use GPS and PPS when no network is available. As it is now, GPS is never used, and when all other clock sources go away, PPS is marked with the fatal 'x' as well.

Here's my current ntp.conf:

refclock shm unit 2 refid PPS minpoll 3 maxpoll 3 flag4 1 prefer

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 1 maxpoll 4 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

After unplugging the Ethernet cable, eventually I get ntpmon output similar to this:

     remote           refid      st t when poll reach   delay   offset   jitter
xSHM(2)          .PPS.            0 l    3    8  377      0ns 559.43us 22.935us
 99.104.170.138  132.163.97.6     2 u 1160  128    0 86.471ms -2.210ms      0ns
 206.55.191.142  .PPS.            1 u 1159  128    0 76.624ms 616.54us      0ns
 2600:3c00::f03c 129.7.1.66       2 u 1160  128    0 62.125ms 900.64us      0ns
 64.22.253.155   173.161.33.165   2 u 1159  128    0 71.788ms 5.5779ms      0ns
xSHM(0)          .GPS.            0 l    -    2  377      0ns -78.66ms 3.7365ms
 pool.ntp.org    .POOL.          16 p    -    8    0      0ns      0ns  1.907us
 162.159.200.123 10.4.0.197       3 u 1159  128    0 25.787ms -1.624ms      0ns
 204.2.134.163   44.24.199.34     3 u 1159  128    0 24.766ms -396.1us      0ns
 199.223.248.101 209.51.161.238   2 u 1159 1024    0 96.084ms 4.4596ms 317.59us
ntpd ntpsec-1.1.8+ 2020-03-04T20:55:58Z        Updated: 2020-03-14T22:31:35 (1)
 lstint avgint rstr r m v  count rport remote address
      0  0.132    0 . 6 2   8897 40414 localhost

Thanks,

-Nick