REMINDER: LEAP SECOND

Doug Barton dougb at dougbarton.us
Mon Jun 22 22:18:14 UTC 2015


On 6/19/15 2:58 PM, Harlan Stenn wrote:
> Bad idea.
>
> When restarting ntpd your clocks will likely be off by a second, which
> will cause a backward step, which will force the problem you claim to be
> avoiding.
>
> There are plenty of ways to solve this problem, and you just get to
> choose what you want to risk/pay.

You misunderstand the problem. :)  The problem is not "clock skips 
backward one second," because most of the time that's not what happens. 
The problem is that most software does not handle it well when the clock 
ticks ... :59 :60 :00 instead of ticking directly from :59 to :00.

THAT problem is avoided by temporarily turning off NTP and then turning 
it back on again when "the coast is clear." Most software can handle the 
"clock skips forward or backwards one second" problem fairly robustly, 
and as Baldur pointed out by doing the reset in a controlled manner you 
greatly reduce your overall risk.

Doug

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