Re: Set your system clock

From: Kirk Strauser (kirk_at_strauser.com)
Date: 02/14/05

  • Next message: Roman Stöckl-Schmidt: "Re: dual boot" 
    To: debian-user@lists.debian.org
Date: Mon, 14 Feb 2005 14:17:07 -0600

    On Sunday 13 February 2005 17:36, Glenn English wrote:

    > OTOH, I don't see any reason not to just turn off ntpd and let cron run
    > ntpdate every hour or so (and at boot). That'd keep your clock accurate
    > with less net bandwidth and resource usage.

    Big reason #1: ntpdate is deprecated and may be removed at any point in the
    future - see http://www.ntp.org/ntpfaq/NTP-s-config.htm for details.

    Big reason #2: ntpdate doesn't guarantee a monotonically increasing system
    time (translation: it may set the clock backwards). Unix systems don't
    like that.

    Big reason #3: ntpd only queries remote servers when it believes the local
    time might have drifted by more than an acceptable amount. If you have a
    very stable clock, then it will ask for the time fairly rarely. A cron job
    knows nothing about this: it asks once per configured time unit, whether
    the local clock is likely to be dead accurate or has already slipped far
    out of sync.

    Big reason #4: if everyone put "0 * * * * ntpdate ntp.example.com" in their
    crontab, then once an hour ntp.example.com gets hammered. This also means
    that those answers are likely to be far more delayed (and therefore
    inaccurate) then they are during the rest of the hour. Besides, the
    ntp.example.com admins would hate you. 

    -- 
Kirk Strauser



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