[ntp:questions] NTP+GPS gone haywire

David Lord snews at lordynet.org
Sun Jan 29 01:27:22 UTC 2012


A C wrote:
> I finally rebuilt my NetBSD box after having lost the partition table on 
> the disk.  I installed 4.2.7-p236 again and everything seemed fine all 
> day yesterday.  Suddenly I get this:
> 
>> $ ntpq -pn
>>      remote           refid      st t when poll reach   delay   
>> offset  jitter
>> ============================================================================== 
>>
>> x127.127.22.0    .PPS.            0 l    2   16  377    0.000  -244.18 
>> 351.567
>>  127.127.28.0    .GPSD.           0 l   65  128  377    0.000  -131866 
>> 2837.34
>>  74.118.152.85   69.36.224.15     2 u  185  512  377   42.681  -128790 
>> 9459.57
>>  64.16.211.38    142.3.100.15     3 u  328  512  377   86.417  -122725 
>> 6592.50
>>  173.244.211.10  131.107.13.100   2 u  196  512  377   55.746  -123465 
>> 6503.82
>>  130.207.165.28  130.207.244.240  2 u  114  512  377   78.525  -131743 
>> 11757.9
>>  131.144.4.10    130.207.244.240  2 u  488  512  377   87.644  -129888 
>> 11647.1
> 
> This happened sometime late last night (I'll have to look at the peer 
> and loop files to see when).  No cron jobs fired off during this period, 
> they had already run yesterday afternoon.  Before this I had offsets for 
> the remote servers in the few milliseconds range and an offset on the 
> PPS signal of only a couple microseconds.
> 
> Anyone have any ideas?  Note that the GPSD refclock is set as "noselect" 
> currently.  I'm trying to test the static navigation feature of the GPS 
> to see if the time offsets calm down on that.  PPS is supplied by the 
> kernel itself.

I had problems when I tried 4.2.7-* recently so I backed out to
either 4.2.6p3 or p5. I was trying 4.2.7.p98 without problem and
also a slightly later version but 4.2.7p239 wasn't usable and I'm
not willing to experiment too much as it might affect my online
servers.

I don't use gpsd either.

Sure GPS (but no different from Garmin 18x-LVC).
NetBSD 5.1_stable, ntp-4.2.6p5

PPSb offset -0.001 jitter 0.003

but offset can increase to 30 usec during cron jobs at 02:00
and 03:00 but is then quickly back to < 5 us.


David



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