You only need to make a connection to an ntp server on a periodic basis (and
you can script it to initiate a dial-up connection).  It doesn't reset your
clock, it changes the "speed" of you clock so that it can minimize drift.
If you are ahead, it will slow you clock down, if you are behind, it will
speed your clock up.  I believe it only affects the OS clock, so unless you
save your system clock to the hardware clock, the changes are lost.  This is
an excellent way to do it, as it avoids time discrepencies in databases and
file modification times.

I my FreeBSD system check time.nist.gov once daily and I haven't seen
anything greater than about a 3 second drift on a bad day.  Incidentally, on
FreeBSD you can do this in a periodic script:

#!/bin/sh

# /usr/local/etc/periodic/daily/100.ntp-timeadj

# If there is a global system configuration file, suck it in.
#
if [ -r /etc/defaults/periodic.conf ]
then
    . /etc/defaults/periodic.conf
    source_periodic_confs
fi

case "$daily_ntp_time_adj_enable" in
    [Yy][Ee][Ss])
        echo ""
        echo "Adjusting system time against ntp server:"
        /usr/sbin/ntpdate time.nist.gov
        rc=0
        ;;

    *)  rc=0;;
esac

exit $rc

And then add:

# 100.time_adjustment
daily_ntp_time_adj_enable="YES"

to your /etc/periodic.conf file.

I am setting this machine up to run as an ntp server for the other machines
on my LAN so that they are all in sync.

Tom Veldhouse
veldy at veldy.net

----- Original Message -----
From: "Troy Johnson" <Troy.A.Johnson at state.mn.us>
To: <tclug-list at mn-linux.org>
Sent: Wednesday, May 16, 2001 11:07 AM
Subject: Re: [TCLUG] Atomic PC Clock


> I know you can use NTP to hook into an upstream time server, but if you
aren't connected all the time or you would just like some
independence/redundancy, this seems like an inexpensive option. I don't
think I will buy one soon, and the only reason I mention it is that I really
thought these things were more expensive than $100.
>
> >>> mend0070 at tc.umn.edu 05/16/01 10:47AM >>>
> On Wed, 16 May 2001, Troy Johnson wrote:
>
> > Anyone use one of these? It might make for a nice cheap NTP server.
> >
> > Anyone know of Linux drivers for these?
> >
> > They seem to sell the docs on the serial data exchange with the unit,
> > so if there aren't any now that could be remedied.
> >
> > http://www.radiocontrolledclock.com/noname4.html
>
> All it does is sync to WWV, I think.  You don't need to spend the money,
> because IIRC you can already do that over the net (and adjust for
> latency).
>
> --
> "To misattribute a quote is unforgivable." --Anonymous
>
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