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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] chrony question about -x option
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Mon, 24 Oct 2022 12:14:33 +0200
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On Fri, Oct 21, 2022 at 06:07:19PM +0200, Hubert Verstraete wrote:
> Hello
>
> I want to use chrony on a host "A" connected to the Internet which should
> act only as a kind of NTP relay to serve the time from an NTP server on the
> Internet to another host "B" on the local network. But I don't want to set
> the system clock of host "A" with this Internet time.
> To achieve this, I plan to start chrony on host "A" with the option -x.
>
> The system clock of host "A" is controlled by another process getting the
> time from the local network.
> Will the Internet time served by host "A" be impacted by the fact that the
> system clock is adjusted by the other process ?
Yes, it will. How much it depends on the stability of the system clock
synchronization. You should make sure it's not synchronized to
something synchronizing directly or indirectly to the chronyd -x
instance. That would work poorly due to a synchronization loop.
> The host "B" needs to synchronize to the raw Internet time in order to keep
> the best accuracy.
Why does host A not have the same requirement and why does B not send
requests directly to Internet?
> Regarding the option -x, in chrony 3.5 there was the following note:
> It is not recommended to run *chronyd* (with or without *-x*) when another
> process is controlling the system clock.
> But this note has disappeared since chrony 4.0.
> Should I understand that what I want to do is feasible with chrony 4.x but
> not with chrony 3.x ?
No, nothing changed in this regard. That recommendation just was not
very practical. It seems people always have some better or worse
reasons to do that and I think it's actually not that different from
other supported but suboptimal conditions like running on a VM with an
unstable clock.
--
Miroslav Lichvar
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