[ntp:questions] NTPD can take 10 hours to achieve stability

Chris Albertson albertson.chris at gmail.com
Mon Apr 18 23:43:47 UTC 2011

On Mon, Apr 18, 2011 at 4:10 PM, Mike S <mikes at flatsurface.com> wrote:
. While it certainly doesn't effect most
> users, it does some. At a minimum, there should be a mechanism to find out
> what (clock divisors?) the kernel has used for calibration, and lock them in
> for use with subsequent boots. Maybe there is, but after searching for a
> while, I couldn't find any way to do that.

Is that not the purpose of the drift file?  It stores the rate that
NTP has using when it stopped. It is checked at startup.

But the best you can hope for is to be "close". The whole reason we
need ntp is because the basic hardware inside the computer is not
stable.  The crystal oscillator runs at a rate that is not constant
and tracks the temperature inside the computer.  So knowing what
worked hours ago may or may not apply.     If you care about micro
seconds then a crystal that has a few parts per million error will
loose or gain a few uS in short order.

In short, it does what you ask but it is not as helpful as you might think

Chris Albertson
Redondo Beach, California

More information about the questions mailing list