[ntp:questions] Re: step-tickers
Richard B. Gilbert
rgilbert88 at comcast.net
Wed Oct 19 18:30:08 UTC 2005
Jarrar Jaffari jjaffari wrote:
>I am really really confused about the file /etc/ntp/step-tickers.
>IN linux /etc/init.d/ntpd script reads it and depending on that it calls
>the servers in the file.
>I have done a plethora of experiments deleting and adding new servers in
>/etc/ntp.conf file with the hope that ntpd will modify the step-tickers
>but it did
>not. Any idea how and who modifies the file ?
>questions mailing list
>questions at lists.ntp.isc.org
On Red Hat, at least, you modify /etc/ntp/step-tickers. In it, you put
the names or IP addresses of the server(s) you wish to use to set your
clock initially. Using it is optional. If you elect not to use it, I
believe your clock is set from the hardware CMOS clock. If the CMOS
clock is within 1024 seconds, about seventeen minutes, ntpd will start
and be able to synchronize the clock. If the CMS clock happens to be
off by five or ten minutes, ntpd will take long time to synchronize.
The advantage of using step tickers is that ntpdate will set your clock
to some close approximation of the correct time (probably within twenty
milliseconds or better) and ntpd will then synchronize fairly quickly. .
Best practice, today, is to use ntpd 4.2.0 with the -g switch which
causes ntpd to set the clock on a one time basis. It does so using the
full filtering and selection algorithms giving maximum protection
against errant servers. In my experience both ways work well and
servers that are badly in error are quite rare.
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