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Date: Fri, 21 Dec 2007 13:24:40 -0500
From: Bill Moran <wmoran@potentialtech.com>
To: John Webster <jwebster@es.net>
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Cc: questions@freebsd.org, "Michael W. Lucas" <mwlucas@blackhelicopters.org>,
	shinny knight <sh1nny_kn1ght@yahoo.com>
Subject: Re: timekeeping on jail servers
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In response to John Webster <jwebster@es.net>:
> 
> --On December 21, 2007 11:23:03 AM -0500 Bill Moran <wmoran@potentialtech.com> wrote:
> 
> > In response to shinny knight <sh1nny_kn1ght@yahoo.com>:
> > 
> > The reason that is not recommended is that it results in sudden steps
> > of the clock.  Occasionally, these steps go backwards.  Software that
> > is very sensitive to time changes (make processes, database servers,
> > anything doing calculations WRT time) can break, crash, or work
> > inaccurately.
> 
> ntpdate -B should slew the time slowly.  (According to the manpage.)

Not generally suitable for cron because it can take longer to slew
than it does for the next cron execution to occur, which would then
result in multiple ntpdate programs fighting each other (not sure
what the effect of this would be).

If you ask me, the -B option is available for people who want to
totally hose timekeeping on their system.

-- 
Bill Moran
http://www.potentialtech.com