Re: [chrony-users] Does Chronyd update the hardware clock?

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On Tue, Jun 10, 2014 at 08:59:41PM -0500, Joe M wrote:
> I presume that the functionality described above has to do with
> setting the "rtcfile" in chrony.conf. Instead of setting "rtcfile" if
> "rtcsync" is used, then does chrony automatically update the hardware
> clock?

With rtcsync, the kernel will write the system time to the RTC every
11 minutes. I think this is usually good enough unless the computer is
down for long periods of time and the network is not available on start.

With rtcfile (which can't be used together with rtcsync) chronyd will
track how much is the RTC off and how quickly it is gaining/losing time.
This alone is not very useful. You will need to start chronyd with the -s
option to use that information and set the system time from RTC on
boot, or at least trim the RTC before shutdown with the trimrtc
command. With the latest chrony prerelease you can also use the
rtcautotrim option to keep the RTC close to the system time, similarly
to rtcsync.

> I tested this by changing my system clock and hwclock to -2 mins. With
> "rtcsync" and starting the chronyd process, it set the system clock
> and the hwclock to the correct time. I just want to confirm that it is
> expected behaviour.

It is.

Miroslav Lichvar

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