Erroneous Leap Second Introduced at 2014-06-30 23:59:59 UTC

[msa at latt.net (Majdi S. Abbas)]

On Mon, Jun 30, 2014 at 05:33:52PM -0700, Tim Heckman wrote:
> I just was alerted to one of the systems I managed having a time skew
> greater than 100ms from NTP sources. Upon further investigation it
> seemed that the time was off by almost exactly 1 second.
> 
> Looking back over our NTP monitoring, it would appear that this system
> had a large time adjust at approximately 00:00 UTC:

	Okay.  Do you have any logging configured (peerstats, etc?) for
ntpd?

> A few of our systems did alert early this morning, indicating they
> were going to be receiving a leap second today. However, I was unable
> to determine the exact cause for NTP believing a leap second should be
> added. And after some time a few of the systems were no longer
> indicating that a leap second would be introduced.

	This can happen if a server is either passing along a leap
notification that it received, or is configured to use a leapseconds
file that is incorrect.

> This specific system is hosted in AWS US-WEST-2C and uses the
> 0.amazon.pool.ntp.org pool.

        0 is just one server in the pool (whichever you draw by 
rotation); is this the only server you have configured?

        --msa