[ntp:questions] Query regarding Ntp 4.2.8 p6, leap second tests

Martin Burnicki martin.burnicki at burnicki.net
Mon Apr 18 11:04:39 UTC 2016


Sowmya Manapragada wrote:
> Hello All,
> Request for inputs regarding a small leap second test which i am trying to
> do with my ntp4.2.8p6..
> 
> Environment :
>    Windows 7 client and windows 7 server test machines in a small networked
> LAN.
> For Leap second configuration referred the following link:
> 
>          :
> http://support.ntp.org/bin/view/Support/ConfiguringNTP#Section_6.14./
> Steps: followed:>
> 
> 1)  Configured leap-second (and  impend leap seconds on Jul 1 Jul 2015)
>   2) server side: included this leapsecond file, and made it as orphan
> server.

You should set the time of your NTP server at least 30 minutes before
the time of the leap second event, e.g. to 2015-06-30 23:30:00 UTC, and
then restart the NTP service. Please note leap seconds are scheduled for
*UTC* midnight, not midnight of some local time zone.

If you set the system time on your NTP server too short before midnight
then ntpd may run in "frequency" mode for a while, and if "frequency"
mode lasts until after midnight then your NTP server may not insert the
leap second properly. See:
http://bugs.ntp.org/show_bug.cgi?id=2838

You can run the command "ntpq -c rv" to check if your server has
accepted the leap second file. If it has then the output should contain
something like:

leapsec=201507010000, expire=201612280000

Also, the output should contain something like "leap=01" during the
hours before the leap second.

>   3) client side:Moved back in time (just for testing) (example> moved back
> to by june 31st 11.56 pm .)

In *any* case you should restart ntpd when you have changed the system
time. Otherwise it will take up to 15 minutes until accepts a time step,
and if the time has changed by more than ~1000 seconds the service will
even stop itself with an appropriate message in the application event log.

Martin



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