Re: Set your system clock
From: Kirk Strauser (kirk_at_strauser.com)
To: firstname.lastname@example.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
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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