Date: Thu, 17 Jun 2004 02:42:01 +0100 From: "Martin O'Nions" <martin.o'nions@catch22.demon.co.uk> To: "'David Magda'" <dmagda@ee.ryerson.ca>, "'Harlan Stenn'" <Harlan.Stenn@pfcs.com> Cc: freebsd-stable@freebsd.org Subject: RE: NTPD and SecureLevel Message-ID: <026c01c4540c$496bd180$021f1fac@ironchurch.com> In-Reply-To: <A8F402E4-BFF6-11D8-AF71-000A95B96FF8@ee.ryerson.ca>
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It's configurable. By default, ntpd will step or 'jump' corrections greater than 128ms and slew anything smaller. Since it's normally running continually in the background, I'd consider it unusual for ntpd to need to make a >128ms correction except perhaps on boot (when any drift in the CMOS clock will need to be rectified). You can however force it to always correct time using slewing by specifying the -x option (bearing in mind it takes 33 minutes to slew 1 second). You can also change the step threshold from 128ms if you really feel the need, using the tinker command in ntp.conf IIRC. If your machine is going to be regularly powered down for a period, then an ntpdate at startup seems reasonable. If it'll be running most of the time though with ntpd active, it shouldn't be making anything more than very minor slewed corrections, albeit on a frequent basis. At least, that's how it's always worked for me... > -----Original Message----- > From: owner-freebsd-stable@freebsd.org [mailto:owner-freebsd- > stable@freebsd.org] On Behalf Of David Magda > Sent: 17 June 2004 01:39 > To: Harlan Stenn > Cc: freebsd-stable@freebsd.org > Subject: Re: NTPD and SecureLevel > > > On Jun 16, 2004, at 20:03, Harlan Stenn wrote: > > >> ntpd(8) doesn't actually change the time by making it 'jump' to the > >> correct time; it slows down or speeds up the rate at which the timer > >> runs at. > > > > Sometimes ntpd will step (jump) the time. > > Yes, I've noticed that as well (it appears in my logs). AFAICT there's > a period of time in which NTPd needs to 'stabilize' and then it slews > the time after that point. It's been a while since I've looked into the > NTP algorithm in detail though. > > You may want to ask about it in the Usenet group > comp.protocols.time.ntp for details. > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"
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