[ntp:questions] NTP client: Sudden time steps on Linux machines

Richard B. Gilbert rgilbert88 at comcast.net
Wed May 2 14:00:54 UTC 2007


Heiko Gerstung wrote:
> Hi Folks,
> 
> I have a problem on a NTP client, it seems to face sudden timesteps and 
> I currently do not have any good explanation for this.
> 
> (NTP Version is ntpd 4.1.2 at 1.892)
> 
> Apr 24 06:56:50 ntpd[13372]: time reset 0.947095 s
> Apr 24 06:56:50 ntpd[13372]: synchronisation lost
> Apr 24 07:23:56 ntpd[13372]: time reset -0.456118 s
> Apr 24 07:23:56 ntpd[13372]: synchronisation lost
> Apr 25 03:56:56 ntpd[13372]: time reset 0.949329 s
> Apr 25 03:56:56 ntpd[13372]: synchronisation lost
> Apr 25 04:23:53 ntpd[13372]: time reset -0.457310 s
> Apr 25 04:23:53 ntpd[13372]: synchronisation lost
> Apr 26 00:57:03 ntpd[13372]: synchronisation lost
> Apr 26 01:15:09 ntpd[13372]: time reset 1.072991 s
> Apr 26 01:15:09 ntpd[13372]: synchronisation lost
> Apr 26 01:38:48 ntpd[13372]: time reset -0.467324 s
> Apr 26 01:38:48 ntpd[13372]: synchronisation lost
> 
> This happens on a few machines running in a classified network and I am 
> not sure if it will be possible to update the NTP on these machines. I 
> just wanted to know if one of you ever came across such a behavior or 
> what good (or not so good) reasons could cause this.
> 
> The logs do not show specific jobs running at those times. According to 
> my customer the time offset will not be corrected when NTP is not 
> running (or is told not to correct the clock), therefore I am quite sure 
> that this is not caused by NTP itself but by some other process / kernel 
> misbehaviour.
> 
> But a 1 second jump every few hours? Wow ...
> 
> Regards,
> Heiko

It doesn't look quite that simple.  It's jumping +1, -1/2, +1, -1/2. 
Something is very wrong there but it's hard to tell what it might be 
from the evidence presented.




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