[ntp:questions] Does NTP cause an abrupt/sudden change in an orphan's system time?

Harlan Stenn stenn at ntp.org
Wed Aug 8 11:20:57 UTC 2012


Arpith Nayak writes:
> What is the corresponding property I need to add in the .conf file to
> cause a gradual sync of time with the public NTP server and not a
> sudden "step"?

I'm going to take the easy way out because it's 0415 here and I need to
fall asleep...

I'd recommend you look at the documentation, as if the "correct" time is
more than 1000 seconds off from the "local" time ntpd will log an error
and exit.  Also remember that while ntpd is correcting for any problems
the timestamps you are logging will be "incorrect", and given that the
slow adjustment means that it will take a bit over an hour to apply a
2-second correction, it could be a very long time to get your machines
in proper sync.

If this situation is "difficult" for you I'd recommend you get an
inexpensive GPS receiver and use that to sync your master machine(s).

Check out the Sure Electronics GPS board, which can be easily modified
to provide a PPS signal.  There are other inexpensive GPS units as well.

H
--
> Regards,
> Arpith
> 
> On Wed, Aug 8, 2012 at 4:33 PM, Harlan Stenn <stenn at ntp.org> wrote:
> 
> > Arpith Nayak writes:
> > > I have a server that is in the orphan mode i.e. it was not connected to
> > the
> > > internet (and thus the various public NTP servers) when I booted it up.
> > Now
> > > if I install ntpd oin this server and run it, will the first instance of
> > > ntpd cause a sudden change in the system time as well as timestamps or
> > does
> > > NTP cause a slow gradual change so that it syncs up with the public
> > server
> > > over a period of time?
> >
> > If you don't override this in the ntp.conf file, it will "step" any
> > change of greater than 128ms as soon as it knows the time.
> >
> > If you override this in the ntp.conf file (or via a startup option) it
> > will slew the time gradually, but realize it may take a *very* long time
> > to get the clock right.  This type of change is applied at 500ppm, so a
> > change of 1 second will be applied over 2000 seconds.
> >
> > H
> >
> 
> --20cf3074d2faef1ca804c6bf1c9b
> Content-Type: text/html; charset=ISO-8859-1
> Content-Transfer-Encoding: quoted-printable
> 
> What is the corresponding property I need to add in the .conf file to cause=
>  a gradual sync of time with the public NTP server and not a sudden "s=
> tep"?<div><br></div><div>Regards,</div><div>Arpith<br><br><div class=
> =3D"gmail_quote">
> On Wed, Aug 8, 2012 at 4:33 PM, Harlan Stenn <span dir=3D"ltr"><<a href=
> =3D"mailto:stenn at ntp.org" target=3D"_blank">stenn at ntp.org</a>></span> wr=
> ote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border=
> -left:1px #ccc solid;padding-left:1ex">
> <div class=3D"HOEnZb"><div class=3D"h5">Arpith Nayak writes:<br>
> > I have a server that is in the orphan mode i.e. it was not connected t=
> o the<br>
> > internet (and thus the various public NTP servers) when I booted it up=
> . Now<br>
> > if I install ntpd oin this server and run it, will the first instance =
> of<br>
> > ntpd cause a sudden change in the system time as well as timestamps or=
>  does<br>
> > NTP cause a slow gradual change so that it syncs up with the public se=
> rver<br>
> > over a period of time?<br>
> <br>
> </div></div>If you don't override this in the ntp.conf file, it will &q=
> uot;step" any<br>
> change of greater than 128ms as soon as it knows the time.<br>
> <br>
> If you override this in the ntp.conf file (or via a startup option) it<br>
> will slew the time gradually, but realize it may take a *very* long time<br=
> >
> to get the clock right. =A0This type of change is applied at 500ppm, so a<b=
> r>
> change of 1 second will be applied over 2000 seconds.<br>
> <span class=3D"HOEnZb"><font color=3D"#888888"><br>
> H<br>
> </font></span></blockquote></div><br></div>
> 
> --20cf3074d2faef1ca804c6bf1c9b--


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