From owner-freebsd-questions@FreeBSD.ORG Tue Apr 21 18:43:40 2009 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E6203106564A for ; Tue, 21 Apr 2009 18:43:40 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout019.mac.com (asmtpout019.mac.com [17.148.16.94]) by mx1.freebsd.org (Postfix) with ESMTP id CEC508FC12 for ; Tue, 21 Apr 2009 18:43:40 +0000 (UTC) (envelope-from cswiger@mac.com) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Received: from cswiger1.apple.com ([17.227.140.124]) by asmtp019.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0KIG00FGNS0S8J70@asmtp019.mac.com> for freebsd-questions@freebsd.org; Tue, 21 Apr 2009 11:43:40 -0700 (PDT) Message-id: From: Chuck Swiger To: Mel Flynn In-reply-to: <200904212033.51524.mel.flynn+fbsd.questions@mailing.thruhere.net> Date: Tue, 21 Apr 2009 11:43:39 -0700 References: <200904211106.01965.mel.flynn+fbsd.questions@mailing.thruhere.net> <200904212023.14365.mel.flynn+fbsd.questions@mailing.thruhere.net> <344D9702-C894-4E54-B256-43FAB17903F1@mac.com> <200904212033.51524.mel.flynn+fbsd.questions@mailing.thruhere.net> X-Mailer: Apple Mail (2.930.3) Cc: freebsd-questions@freebsd.org Subject: Re: Preventing ntpd from adjusting time (backwards) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Apr 2009 18:43:41 -0000 On Apr 21, 2009, at 11:33 AM, Mel Flynn wrote: > On Tuesday 21 April 2009 20:29:18 Chuck Swiger wrote: >> On Apr 21, 2009, at 11:23 AM, Mel Flynn wrote: >>> Now I'm also wondering how ntpd handles securelevel 2. >> >> "man init" suggests that stepping the clock by more than a second is >> disallowed: > > yes, so does it bail or retry till skew wins over the failed steps? The attempt to step the clock will fail. ntpd should continue to run, but the rate of skewing is typically limited to 1 second of correction over a time interval of 2000 seconds. If your clock routinely drifts by more than 1 second every hour or so, ntpd is unlikely to be able to correct the time at all under securelevel 2. If your clock drift is less, ntpd should eventually manage to sync time, but for extreme cases, running ntpdate periodically to forcibly reset the clock might be needed (and to run ntpdate after boot, you'd need to back down to securelevel 1). Regards, -- -Chuck