Date: Tue, 22 Apr 2003 13:00:22 -0700 From: Kent Stewart <kstewart@owt.com> To: David Kelly <dkelly@hiwaay.net>, Charles Swiger <cswiger@mac.com> Cc: FreeBSD-Questions@freebsd.org Subject: Re: Accurate time without a network connection? Message-ID: <200304221300.22051.kstewart@owt.com> In-Reply-To: <20030422194413.GC13774@grumpy.dyndns.org> References: <20030422184554.GA13432@grumpy.dyndns.org> <4B518202-74F8-11D7-BCB7-003065ABFD92@mac.com> <20030422194413.GC13774@grumpy.dyndns.org>
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On Tuesday 22 April 2003 12:44 pm, David Kelly wrote: > On Tue, Apr 22, 2003 at 03:26:19PM -0400, Charles Swiger wrote: > > Ok. If you run NTPD with only the local hardware clock for a > > reference, wait for a week, and then see how the intrinsic drift of > > the hardware compares with "real time" (using your watch or some > > other time source), you can adjust /etc/ntp.drift by hand. This > > isn't going to be perfect, but it's going to be much more accurate > > than doing nothing. > > Good. But already tried that. The situation is multiple systems have > to run with something near the same time, but no bidirectional > contact. And need to operate for years. Letting ntpd tune itself and > then free run works much better than the system clock alone but only > good for weeks, not months. > > As for exactly what time the systems have, it doesn't much matter as > long as they all have the same time. It sounds like you really need an external clock that is very stable. There was a discussion on -hackers a long time ago about doing something like that. I think they were using a gps based clock for a reference. If you don't have access to a common time, nothing short of access to WWVB (the Navy Time Radio Station) would keep your time current. Kent -- Kent Stewart Richland, WA http://users.owt.com/kstewart/index.html
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