| Re: [chrony-dev] can chrony adjust H/W clock too ? |
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On Wed, 21 Apr 2010, J. Bakshi wrote:
On Tue, 20 Apr 2010 21:09:54 -0700 (PDT)
Bill Unruh <unruh@xxxxxxxxxxxxxx> wrote:
On Wed, 21 Apr 2010, J. Bakshi wrote:
Thanks a lot for your clarification and suggestion. Then I do
continue with the corn - way as you suggest. I understand as ntp
chrony has been designed to address the system time. Maybe in
future it can also take care of rtc clock too as rtc clock has its
own importance on the system and an accurate rtc clock is always a
must.
Well, no, an accurate rtc is not really a must. Especially with
chrony. You can tell chrony to query a remote ntp source and if the
time is out by more than x, it will step the time. If less, it will
slew the time, quite rapidly. (chrony converges much faster than does
ntpd) Thus it is not really important that the rtc be accurate. But
as I said, chrony can use the rtc to start up relatively accurately
( but you cannot use ntp and hwclock together. Neither knows about
the other)
Yes I agree with you. The objective is to sync with ntp. But I might be permitted dreaming that one day chrony can adjust the rtc too.
\
Unfortunately no. The rtc has absolutely no mechanism to adjust its rate. That
is entirely determined by the clock crystal that is tied to the rtc. chrony
can determine how much that rate differs from "one second per second" but it
cannot influence it. This is especially true because the only time the rtc is
used is when the computer is off, and no program, like chrony, can run. All it
can do is compensate for what I thinks is the rate difference of the rtc. Even
that is only partial because the temp of the crystal ( which determines its
rate) is different when the computer is off, and there is no way of knowing
what that temperature was.
Thanks
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