[ntp:questions] Time reset

Richard B. Gilbert rgilbert88 at comcast.net
Thu Apr 3 21:10:24 UTC 2008

jkvbe wrote:
> The ntp log file shows when NTP steps the time. But then the potential harm
> is already done. Especially if the time moves backward, our server might
> have serious trouble. Is there a log event which indicates that the time is
> going to be reset in order to enable us to take appropriate action before
> the actual reset?
> Thanks a lot,
> Jan

I don't know of any advance warning.

DOES the time step backward?

If ntpd is working properly it should NOT need to step the time at all 
with the possible exception of a single step when ntpd is first started.

If ntpd is stepping time regularly, you have some other problem.  If you 
find and fix that problem, ntpd should stop stepping the time.

There are/were known issues with some Linux systems; during periods of 
high disk usage, clock interrupts would be lost resulting in a FORWARD 
step.  AFAIK these issues were related to EIDE disks used in PIO mode 
rather than DMA mode.  ISTR reading that the problem has been fixed in 
recent versions of Linux.  YMMV

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