[ntp:questions] PPS not working on newer kernel/distros
joachim.fabini at tuwien.ac.at
Tue Oct 9 09:43:10 UTC 2018
Which version of ntp is deployed on your system?
Any relevant/suspect output in syslog when restarting ntpd?
What does ntpq report?
First guess: please remember http://bugs.ntp.org/show_bug.cgi?id=3367 -
this was staged (only) for ntp-4.2.8p11. Make sure that either your ntp
has the patch already or patch your sources manually.
On 10/09/2018 01:26 AM, Brandon Applegate wrote:
> For years I’ve have ntpd+NMEA+PPS working great. My OS was Ubuntu server 12.04 - and then (currently) 14.04. GPS is a Garmin LVC 18x.
> I use setserial to set low_latency, I’ve reduced the NMEA sentence to bare minimum, etc. All the usual tweaks. All of this going into a real UART serial PCI slot board (no USB) on a full size PC.
> My relevant ntp.conf for this:
> server 127.127.20.0 mode 1 minpoll 4 maxpoll 4
> fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 time2 0.600
> I decided to try to upgrade, and hit nothing but roadblocks. So far I’ve tried both Debian 9 and Ubuntu 18.04. What I observe is that my GPS offset steadily climbs and climbs. It never seems to decrease. I’ve also tried the above config with flag3 set to 0 (“soft” PPS). In all of these cases I’ve verified with ppswatch that I have pps coming in on the port. It really seems like something has changed in the kernel in the past few years that’s causing this. It’s about the only thing I can think of as a variable. I’ve tried distro ntpd packages as well as compiling a few versions of the latest source. All with the same behavior.
> Anyone have any ideas what could cause this behavior ?
> Brandon Applegate - CCIE 10273
> PGP Key fingerprint:
> 0641 D285 A36F 533A 73E5 2541 4920 533C C616 703A
> "For thousands of years men dreamed of pacts with demons.
> Only now are such things possible."
> questions mailing list
> questions at lists.ntp.org
More information about the questions