Leap seconds

Hal Murray hmurray at megapathdsl.net
Sun Jan 14 23:05:51 UTC 2018

paul at anastrophe.com said:
> So, I'm confused. Should I employ ntpleapfetch from cron and include the
> leapfile directive in my ntp.conf? Or is it best to exclude all of this  on
> a public NTPsec server?

Debian distributes a copy of the NIST leap file in
It's part of the tzdata package.

I don't know how well they keep it up to date, but my copy looks good.


ntpd should work correctly with or without a leap file.

The leap pending info is sent in the NTP reply packets.  The client takes a 
majority vote.  I think that's distributed a month early and passed to the 
kernel a day early.

If you have a valid leap file, it ignores the network info and believes the 

You can also get the leap-pending info from some refclocks.  I'm not sure of 
the priority of refclock vs leap-file.  I suspect the refclock gets OR-ed 
with the network info.

Historically, there have been bugs in leap info from refclocks and from the 


Is there a standard way to run cron jobs at random days/times?

These are my opinions.  I hate spam.

More information about the users mailing list