REMINDER: LEAP SECOND

Nick Hilliard nick at foobar.org
Tue Jun 23 17:54:42 UTC 2015


On 23/06/2015 18:23, shawn wilson wrote:
> NTP causes jumps - not skews, right?

this is implementation dependent.  For normal clock differences on ntpd,
if you start it with the -x parameter, it will always slew and never step.
 If you start ntpd without the -x parameter, if the calculated correct time
after slewing is out by > 128ms relative to other ntp servers, then after
900 seconds, it will step to the correct time.

However in the case of leap seconds, if the operating system implements ntp
kernel discipline, then the ntp server will immediately step by the leap
second (forwards or backwards), as soon as it receives the leap second
notification.  It does this on the basis that the kernel supports leap
seconds, therefore it's probably the right thing to do.

Nick



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