Date: Wed, 19 Jan 2000 19:28:13 +0100 (CET) From: Oliver Fromme <olli@dorifer.heim3.tu-clausthal.de> To: freebsd-questions@FreeBSD.ORG Subject: Re: time sync problem--ntpdate AND xntpd?? Message-ID: <200001191828.TAA22610@dorifer.heim3.tu-clausthal.de> In-Reply-To: <864n5j$30mu$1@atlantis.rz.tu-clausthal.de>
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Sean Noonan <snoonan@cx952600-a.fed1.sdca.home.com> wrote in list.freebsd-questions:
> [...]
> Until I read this in man ntpdate: "Ntpdate will decline to set the date
> if an NTP server (e.g. xntpd(8)) is running on the same host".
>
> So, what should I do? It didn't/doesn't make sense to me to have all of
> my worksatations use internet bandwidth to check time; better to have one
> check the time and the the rest get their time from it.
>
> What am I missing, conceptually? What are my alternatives? Is their a
> NTP proxy I could run on my firewall?
"ntpdate" sets the clock just once and then exits.
"xntpd" is a daemon which runs in the background and corrects
the clock continously. It synchronizes with one or more
servers on the net every now and then (it doesn't take much
bandwidth, so there is no reason to worry). It's even clever
enough to calculate the drift of your local clock, so it can
correct it even if there is no network connection for some
time.
However, "xntpd" only works if the clock is "about right"
already. It refuses to touch the clock if the deviation is
larger than 5 minutes, because in that case it thinks that
something is seriously wrong. "xntpd" tries not to make
"steps", but rather speeds the local clock up slightly or
slows it down slightly, in order to correct for the drift.
Therefore, you usually run _both_ "ntpdate" and "xntpd".
First "ntpdate", in order to correct the clock once, no
matter what. The you run "xntpd" in the background to
keep the time in sync with the world.
In FreeBSD, this is pretty easy to configure, just set
ntpdate_enable and xntpd_enable both to "YES" in your
/etc/rc.conf file (see /etc/defaults/rc.conf for the default
values). Then you'll have to create an /etc/ntp.conf file
(see the manpage for details) which contains the servers
which you want to use for NTP.
Note that "xntpd" can be used as a server and as a client,
or both at the same time. That is, you can run xntpd in
server+client mode on one box which syncs with some NTP
servers out there on the net. Then you can run "xntpd"
clients on other machines of yours to sync to your server.
Regards
Oliver
--
Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany
(Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de)
"In jedem Stück Kohle wartet ein Diamant auf seine Geburt"
(Terry Pratchett)
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