| Re: [chrony-users] Requesting some insight regarding preferred servers and RTCSYNC/RTCFILE |
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William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
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On Mon, 29 Oct 2018, Miroslav Lichvar wrote:
On Mon, Oct 29, 2018 at 10:04:02AM +0000, Martin Janse wrote:
My first concern lies with the RTC. In the current configuration, neither RTCSYNC nor RTCFILE are defined. Does Chrony still correct the system time while it's running? Or only at boot? Or never?
If no rtcfile or rtcsync is in the config, chronyd will not care about
the RTC at all. It will not track its frequency offset relative to the
system time, and correct for drift with the -s option, or tell the
kernel to synchronize it. If the RTC drifts, the initial time on start
will be wrong.
I guess that's what you want as you seem to synchronize the system
clock to (the same?) RTC using a SOCK refclock.
No idea why youu would want to do that. Your rtc drifts, and in particular
drifts when the sytem is off.
On boot chrony reads the rtc when chrony is first started and sets the system
time to that. After that the rtc is ignored except that the system will
calculate the rate and offset of the rtc. The rtc typically is a pretty shitty
source for time. It can drift badly.
Secondly, a new feature needs to be added to the system. Other than syncing to the RTC or other devices on the network, an NTP server needs to be added that has precedence over any other source. I saw in the manual that the parameter 'prefer' can be added to the server, causing Chrony to prefer that server. However, is there a scenario where Chrony still picks a non-preferred source? Is there a degree of 'quality' that the preferred server needs to have in order to have guaranteed precedence?
chronyd can select a non-prefered source if it doesn't agree with
other sources (falseticker). If you had only two sources, an RTC and
I think that sentence is open to confusion. If chrony sees that majority of
the clocks show one time and a minority show substantially different times (ie outside
the error bodget of the majority) , then that minority are false tickers. If
the prefer souce is in that minority, then chrony does not trust it and uses
one of the majority as its source.
are
an NTP server, it would be easy for them to not agree and chronyd
would stop synchronization.
I would expect chrony to choose the prefer option in that case. Is that wrong?
To always select the source, it needs to be specified with the "trust"
option.
Or just have it as the only source.
--
Miroslav Lichvar
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