Re: [chrony-users] Leap second coming up.

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

On Mon, Dec 19, 2016 at 11:38:34AM +0100, Ben Kochie wrote:
> So there is a leap second coming up, I had a couple questions about the
> chrony behavior.
> 
> When running more than one tier of chrony.  Say I have 5 servers syncing to
> stratum 1 servers in pool.ntp.org, and a number of servers syncing to those
> 5 behind a firewall.
> 
> Do I configure the 5 external stratum 2 servers to handle the leap second,
> or do I configure the internal slaves?  Or both tiers?

It depends on how exactly you want to handle the leap second.
The standard approach would be to handle it by stepping on all servers
and pass the leap bits to their clients so they can do the same.
That's the default behaviour of chronyd.

If you need the clients to slew their clocks in the same way, but they
can't be configured to do so (e.g. because they running ntpd or older
chronyd which doesn't have the leapsecmode directive), you could
configure the 5 external servers to perform the "leap smear"
(leapsecmode slew + smoothtime leaponly), so their clients wouldn't
even know there was a leap second. In this case only one tier would do
that and it's important that clients of these servers are not polling
anything else that could leak the real leap bits.

-- 
Miroslav Lichvar

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