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

[Heiko Gerstung]

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