Date: Wed, 9 May 2007 18:40:32 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-stable@FreeBSD.ORG Subject: Re: clock problem Message-ID: <200705091640.l49GeW9q055050@lurza.secnetix.de> In-Reply-To: <8EA8AB80-786A-431C-BFFD-6E244D3E25E8@goldmark.org>
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Jeffrey Goldberg wrote: > Oliver Fromme wrote: > > Martin Dieringer wrote: > > > Oliver Fromme wrote: > > > > Are you sure that your /etc/ntp.conf ist correct? > > > > > > # cat /etc/ntp.conf > > > > > > server time.fu-berlin.de iburst maxpoll 9 > > > driftfile /var/db/ntp.drift > > > logfile /var/log/ntpd > > > > You must add "restrict" lines for every server and for > > localhost, like these: > > > > restrict time.fu-berlin.de nomodify > > restrict 127.0.0.1 Sorry, I forgot one line: restrict default ignore > Why? The "default" line is for security reasons, so nobody else can modify your ntpd. The "nomodify" line enables time synchronization with the server, but prevents it from being able to modify your ntpd settings. Finally, the line for localhost enables you to use tools like ntpdc and ntpq locally. It's all explained in the ntp.conf(5) manual page. > > Other than that, the config looks good. There's no need > > to add further time servers. > > The time adjustment algorithms of NTP make use of multiple time > sources. NTP works best with having at least three reachable > servers. Of course ntp is designed to keep good time even when you > are disconnected from the net, but it builds up its data from > multiple sources and using triangulation to correct for errors. NTP works perfectly well with a single source. Having multiple sources is not necessary on an end client (but it doesn't hurt either, of course). Of course, on a server that provides NTP service itself to a subnet or similar, having multiple upstream servers is desirable. In fact, ntpd refuses to synchronize against a server that does not have at least two upstream servers (non- stratum-16) itself. Martin's Problem with ntpd is not a precision problem. His problem is that his ntpd does not synchronize at all. Adding more servers certainly won't solve that problem. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "In My Egoistical Opinion, most people's C programs should be indented six feet downward and covered with dirt." -- Blair P. Houghton
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