[ntp:questions] ntpd goes into oscillation

unruh unruh at wormhole.physics.ubc.ca
Wed Dec 30 18:18:10 UTC 2009

On 2009-12-30, David J Taylor <david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid> wrote:
> "unruh" <unruh at wormhole.physics.ubc.ca> wrote in message 
> news:slrnhjkta6.4e4.unruh at wormhole.physics.ubc.ca...
>> ntpd has suddenly broken out into oscillations. it is fed by a Garmin
>> 18 LVC PPS via shm. The oscillation has a period of just under an hour (
>> about 50 min) and an amplitude of about 10usec. in the offsets (
>> amplitude of about .005PPM in the rate). Since this is acting as the
>> clock for a number of other machines, they are also showing the
>> oscillation especially in the rate.
>> While I suppose this could be something in the GPS itself, it looks more
>> like an oscillation in ntpd.
>> Nothing changed when the oscillations started. Ntpd had been started
>> on Dec 14, and this change began on Dec24.
>> You can see the graph on www.theory.physics.ubc.ca/chrony/chrony.html ,
>> the graph for the machine called string.
>> Has anyone else ever seen this kind of thing?
> Something similar, perhaps, yes, and I reported it here before.
> It seems that NTP hits the +/- 500 ppm drift limit and can't recover - 
> check the drift file contents.  You might try deleting (or renaming) the 
> drift file.  I haven't seen this for some time, though.  What version are 
> you running?

Nope, the drift is NOT at the limit ( it is at about 200) 
ntp 2.4.2p4

> Cheers,
> David 

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