This is incorrect advice (Re: ntpdate from cron -- DON'T DO THAT!)
On Sat, 2002-12-21 at 17:51, N. Thomas wrote:
> Contrary to what you may have heard, ntpdate does not keep your system
> clock synced. Also ignore the foolish recommendations to run ntpdate
> from a cron job.
> ntpdate works like date(1), but it sets your clock's time to that of an
> ntp server (or servers) instead of having it specified by you.
I think you haven't looked at ntpdate in a while. From the ntpdate(1)
Time adjustments are made by ntpdate in one of two ways. If
ntpdate determines the clock is in error more than 0.5 second it
will simply step the time by calling the system settimeofday(2)
routine. If the error is less than 0.5 seconds, it will slew the
time by calling the system adjtime(2) routine. The latter technique
is less disruptive and more accurate when the error is small, and
works quite well when ntpdate is run by cron(8) every hour or two.
In fact, you can *force* ntpdate to slew the clock rate to achieve
accuracy rather than stepping it; see the '-B' option.
Having said that, I'd still recommend ntpd of ntpdate for syncing system
clocks, particularly on important machines. Still, ntpdate isn't nearly
as naive as you make it out to be.
Kirk Strauser <email@example.com>