On 2015-02-10, Jochen Bern <jochen.b...@linworks.de> wrote:
> On 02/10/2015 06:15 AM, catherine.wei1...@gmail.com wrote:
>> However, when I wait for several minutes, the time can be adjusted to
>> the right time. I couldn't see the gradual changes of offset. Is that
>> normal?
>
> Assuming that you're using a minimalistic configuration: Yes.
>
> ntpd would take almost three months to *gradually* eliminate (slew) one
> hour of offset, so as soon as the
> offset-from-hell-that-struck-us-out-of-the-blue-sky was confirmed, it
> gave up all hope for the universe and "just set the clock" hard (step).
No. It only does that for "offsets from Hades". The Ones from Hell, ntpd
abandons all hope and quits. ( Hades is 128ms to 1000 sec, Hell is
>1000 sec)
Ie, for <128ms, ntp will try to slew the clock ( at a max of 500PPM- as
far as I can see a completely arbitrary limit Mills decided on decades
ago). If >128ms but <1000s it will, after being sure that that is not
just some measurement error, jump the time (ie infinite PPM) If >1000 it
assumes something is very very very badly wrong, and aborts.
However if this is the first time this running of ntpd has encountered
this, eg at startup, if you use -x option it will jump the time even if the
offset is >1000 sec.
>
> Regards,
> J. Bern
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