From owner-freebsd-questions@FreeBSD.ORG Tue Apr 22 13:00:32 2003 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 065A537B4D4 for ; Tue, 22 Apr 2003 13:00:32 -0700 (PDT) Received: from rutger.owt.com (rutger.owt.com [204.118.6.16]) by mx1.FreeBSD.org (Postfix) with ESMTP id 13B7E43F85 for ; Tue, 22 Apr 2003 13:00:31 -0700 (PDT) (envelope-from kstewart@owt.com) Received: from topaz-out (owt-207-41-94-233.owt.com [207.41.94.233]) by rutger.owt.com (8.11.6p2/8.9.3) with ESMTP id h3MK0MV24034; Tue, 22 Apr 2003 13:00:22 -0700 From: Kent Stewart To: David Kelly , Charles Swiger Date: Tue, 22 Apr 2003 13:00:22 -0700 User-Agent: KMail/1.5.1 References: <20030422184554.GA13432@grumpy.dyndns.org> <4B518202-74F8-11D7-BCB7-003065ABFD92@mac.com> <20030422194413.GC13774@grumpy.dyndns.org> In-Reply-To: <20030422194413.GC13774@grumpy.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200304221300.22051.kstewart@owt.com> cc: FreeBSD-Questions@freebsd.org Subject: Re: Accurate time without a network connection? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Apr 2003 20:00:32 -0000 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