Re: [chrony-users] Requesting some insight regarding preferred servers and RTCSYNC/RTCFILE

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

On Mon, Oct 29, 2018 at 03:30:30PM +0000, Martin Janse wrote:
> First off, I do understand that keeping time on a closed system without a dedicated, reliable time source is basically impossible and simply means that the time of that network will be unreliable. It is not clear to me yet, if defining RTCSYNC would improve the reliability by some degree. As far as I understand, RTCSYNC does not actually change the RTC time but rather compensates for the drift of the RTC when setting the local time. Since the system has an uptime of >99%, would this help?

rtcsync just tells chronyd to tell the kernel that it should keep the
RTC synchronized to the system time. If the system clock was
synchronized to the RTC using the SOCK refclock, it would create a
synchronization loop. That would be bad.

> As for the querying of other devices; unfortunately, I do not know how this works either. I can see that the DUM1 socket is defined together with the RTCC socket, but what they are used for I do not know.

There used to be a bug where chronyd didn't work with multiple SOCK
refclocks. A workaround was to specify dummy reflocks before the real
ones. Maybe this is a remnant of the workaround.

-- 
Miroslav Lichvar

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