[ntp:questions] Leap second preparedness

Dave Hart hart at ntp.org
Fri Jun 29 23:57:27 UTC 2012

I know, leap second preparedness is like sneeze preparedness to people
who have a life.  But if you care about the pending hole in computers'
timeline, in about 2 minutes ntpd systems around the world will begin
announcing leap=01 instead of leap=00.  If you are responsible for any
ntpd instances, you might spot check to be sure they are in fact
announcing the insertion a day in advance as intended.  This is
particularly important for NTP servers relied upon by others.

If you find a system which is still advertising leap=00, you can
correct it by configuring a leapfile, assuming non-ancient ntpd
versions.  See:


If your ntpd is relying upon other NTP servers (that is, is stratum 2
or higher), it will not announce the pending leap second starting
exactly at midnight UTC in a few minutes, but should within a few
polling intervals.  With the default maximum interval of 1024 seconds
being about 17 minutes, by 00:34 30-June UTC most systems should have
picked it up that will.

Dave Hart

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