| Re: [chrony-users] Chrony server transition behavior |
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On Mon, 16 Nov 2020, Antoine Sgambato wrote:
I am trying to understand how chrony transition from a time server.
Lets consider a Chrony client synchronized with a sole and unique server. Synchronization is established with no problem.
Now I remove this server from my chrony configuration (with the chronyc delete command). I expect my Chony client to become either in local or un-synchronized state (depending on whether the local mode has been enabled or not).
And it does so, but it takes some time : As soon as the server is deleted from my config, I have a log that says "Can't synchronise: no selectable sources" (and chronyc sources returns an empty list) but the tracking command says it is still synchronized with the server for well other than 2 hours before switching to the local mode (in my case).
Of course. It is not going to consider itself unsynchronized as soon as the
source disappears. It has no idea why the source disappeared. It is set up to
run for possibly hours before it starts to wander away from UTC. Note that if
your poll is 10, that is 2^10 sec which is 1/3 of an hour, and it would
certainly feel itself to be fine for a few missed periods ( ie hours). Chrony
is NOT a parrot, simply repeating what it got from its sources. It is a way of
disciplining your local clock so that its time is the same as UTC. AFter a
while, of not getting any updates it will finally decide that its own time has
possibly drifted (depending on the uncertainties of the rate and of the time)
far enough away from UTC that it no longer trusts its own time.
I suspect that, as the synchro was well established (drifts parameters have been calculated and stored in the drift file), Chrony considers itself as still synchronized with a source for some time even if the is no more communications with this source.
Is this reasoning correct? and are there some configuration parameters that affect this delay?
Yes, the reasoning is correct.
What is it that you are trying to do, or test?
Thank you for any clarification!
Antoine.
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