[ntp:questions] Google and leap seconds

Marco Marongiu brontolinux at gmail.com
Wed Sep 21 07:26:07 UTC 2011


Thank you all for the interesting answers!

I'd have one more question. Wouldn't it be convenient for ntpd to have
an option, so that users may refuse to step back the clock in case of a
leap second, and adjust the clock speed instead?

I understand the risk for this: systems in two subnets, each of which
uses a different approach, will find them out of sync for a while after
the leap second is inserted/deleted. Depending on the applications
involved, this may have bad side effects. But is the current situation
any better?

Almost all here seem to agree on the fact that POSIX systems don't
manage leap second insertion the right way. This seems almost impossible
to fix because of the epoch definition. From the top of my head, I don't
see any way to redefine the epoch to keep into account leap seconds,
without breaking the compatibility in all directions (with older version
of the same OS, or with another OS adhering to POSIX in this regard).

If we accept that Google did the only thing they could do to avoid
problems related to leap seconds, wouldn't it be good for ntpd to
support such a behaviour "in bundle"?

-- bronto

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