Re: ntpdate / ntpd

From: Tauno Voipio (tauno.voipio_at_iki.fi.SPAMBAIT_REMOVE.invalid)
Date: 11/21/03 

Date: Fri, 21 Nov 2003 15:19:51 GMT

"noone" <noone@noone.org> wrote in message
news:o0Tub.18224$aT.1687@news-server.bigpond.net.au...
>
> In the data centre, I have about 8 SPARCs running Solaris8.
> Each of them are running ntpdate via cron every 10 minutes.
> The NTP server used is internal to the data centre, which then
> synchronises its time with external NTP servers in the internet.
>
> I have 1 linux box, running RH 7.2, using ntp from RH 7.3. The time on
> this box is advanced by 1 minute and a few seconds compared to the
> SPARCs. The file /etc/ntp.conf has the server line point to the internal
> NTP server, like this:
>
> server 10.0.10.37
>
>
> Restarted ntpd ( /etc/rc.d/init.d/ntp stop; /etc/rc.d/init.d/ntp start
> ). Now after one day, the time on the linux box is still not in sync
> with the rest of my boxes, the SPARCs, and ntpd is still running.
>
> Of course, if I run ntpdate 10.0.10.37, then the time on the linux box
> is "corrected" and in sync with the rest.
>
> So question is, why ntpd did not ( or take a long time ) to "correct"
> the time ?

IMHO, the proper method is to initially sync at boot with ntpdate and let
ntpd then handle the rest. ntpd is better than a cron job, as it prevent
sudden time jumps and uses slow slewing instead so that no process will ever
see time reversing or jumping. Also, ntpd adjusts the poll rate to a
suitably sparse rate as soon as it is sure for a good sync.

The Solaris thingies should also use NTP. Now, at each cron time they risk a
time jump.

For a local network with limited delay, a solution could also be broadcast
NTP from the local server, e.g. at 20 min intervals. However, with less than
hundreds of clients, even a server behind 10 Mbit/s cable can well handle
standard NTP.

For more information of NTP, go to <http://www.ntp.org/>.

HTH

Tauno Voipio
tauno voipio @ iki fi

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