Gerriet M. Denkmann wrote:
On 31 Oct 2014, at 15:30, Kenyon Ralph <[email protected]> wrote:
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On 2014-10-31T14:57:46+0700, "Gerriet M. Denkmann" <[email protected]> wrote:
My computer (OS X 10.10) runs ntpd.
ntpd --version
ntpd - NTP daemon program - Ver. 4.2.6
It writes the drift value I am interested in to
/private/var/db/ntp.drift at shutdown and one hour after start/
change of ntp servers.
But I would like to know the current value of the used drift (just
idle curiosity).
How?
Can one force ntpd to write the current value to ntp.drift? Can ntpq
be of help?
This is more of a question for the NTP questions list rather than this
pool list, but...
Sorry for using the wrong list!
The value in the drift file is a snapshot of the clock frequency.
Precisely, it's the frequency offset ntpd has determined and now applies
to the system clock to minimize the drift of the system time.
You
can see the current frequency in the output of "ntpq -c rv", or "ntpq
- -c 'rv 0 frequency'" for just the frequency. See
http://doc.ntp.org/4.2.6p5/ntpd.html and Clock Discipline Algorithm in
the current docs: http://www.eecis.udel.edu/~mills/ntp/html/warp.html
Please note the absolute value of the frequency offset depends only on
the frequency offset of the oscillator on the main board, on which the
system timekeeping is based.
The absolute magnitude is not very important since it's just determined
and compensated by ntpd. Very much more important is how the oscillator
frequency varies over time, e.g. depending on variations of the ambient
temperature inside and outside the PC housing.
If the variations are low then time drifts only slowly and can easily be
compensated by ntpd, but if the variations are high then ntpd has to
apply larger corrections.
If you have loopstats enabled then the loopstats files also tell you if
the frequency offset varies more or less.
Martin
--
Martin Burnicki
Senior Software Engineer
MEINBERG Funkuhren GmbH & Co. KG
Email: [email protected]
Phone: +49 (0)5281 9309-14
Fax: +49 (0)5281 9309-30
Lange Wand 9, 31812 Bad Pyrmont, Germany
Amtsgericht Hannover 17HRA 100322
Geschäftsführer/Managing Directors: Günter Meinberg, Werner Meinberg,
Andre Hartmann, Heiko Gerstung
Web: http://www.meinberg.de
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