[ntp:questions] Leap second bug?

Martin Burnicki martin.burnicki at meinberg.de
Thu Jan 10 10:35:03 UTC 2008

Spoon wrote:
> I've just noticed the output of dmesg.
> Clock: inserting leap second 23:59:60 UTC
> (on two different systems)
> The strange part is that, on one system, the line does not show up
> in kern.log, while on the second system, it does:
> Jan  8 16:16:05 kernel: Clock: inserting leap second 23:59:60 UTC

That's normal. If ntpd has passed a leap second announcement to the kernel
then the kernel handles the leap second.

Of course whether the message appears or not depends on the implementation
of the kernel. 

Alternatively the kernel of one of the machines may not have received a leap
second announcement. Ntpd also does some plausibility checks (e.g. leap
second only possible at the end of June/December) before it passes the
announcement to the kernel.

And, also the source code of ntpd has changed over time, so the exact
behaviour depends also on the version of ntpd ...

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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