Re: [chrony-users] (Mis?)Understanding maxchange config line

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

On Fri, Dec 17, 2021 at 06:34:12PM +0000, Emory.Nolte@xxxxxxxxxxxxxxxxxxx wrote:
> Hi,
> 
> Trying to diagnose issues or misunderstanding with using the "maxchange" option in the config file. I want to use "maxchange 1000 start ignore" to quit if the time offset is more than 1000s.
> 
> When trying to use the other two parameters however, it seems that setting start to anything other than 0 will cause to never chrony to never exit. Doing some debugging, the value used for "offset" in the comparison to the offset parameter in "maxchange" drops to a few milliseconds after the first clock cycle even though the system time is still ~2000s off the source time.

The description of the maxchange directive needs some improvement. It
applies to the client's NTP clock, not the system clock. If the
initial offset is 1000s, the first update of the clock corrects it by
1000s. The offset on the second update would then normally be expected
to be close to 0. It doesn't matter that the system clock was
corrected only by a small fraction of the offset between the two
updates.

In a test you would need to insert a large offset to the server clock
after the client made the first update.

-- 
Miroslav Lichvar


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