[ntp:questions] once 'ntpd' stops, does the drift file value continue to get used for clock adjustments?

David Woolley david at ex.djwhome.demon.invalid
Thu Mar 17 22:29:06 UTC 2011

Gautam Thaker wrote:
> I have a stable drift value on my fedora 12 node and everything is
> running well. (offsets are well below 1msec). If I now stop 'ntpd'
> will my time start to drift relative to the 'correct time' by the PPM
> value in the drift file? Or is it that ntpd has already set things up

Depends on whether or not you are using the kernel time discipline. 
Some people set tinker values that cause the kernel discipline to be 
turned off, and it is not supported on all platforms.

Windows will probably retain the last correction, but this may include a 
  high frequency component.

The non-kernel discipline on Unix relies on ntpd actively injecting 

> so that corrections as per last value of drift file will continue
> indefinitely? If it is the latter and if indeed my drift value is
> quite good (as ntpd had run for many days already), it seems I can go
> for many more days w/o ntpd and not get very much out of sync at all.

ntpd takes advantage of this by ramping up the poll interval.

More information about the questions mailing list