[ntp:questions] Purpose of a leap second file?

David J Taylor david-taylor at blueyonder.co.uk.invalid
Thu Feb 16 06:53:49 UTC 2012

"A C" <agcarver+ntp at acarver.net> wrote in message 
news:4F3CA0A1.5070506 at acarver.net...
> Given the recent thread here about the upcoming leap second, I wanted to 
> know what additional service/value the leap second file provides that 
> isn't handled by ntpd receiving a message to add or remove a second.  I 
> understand the generic ntpd documentation includes a flag to add a leap 
> second so it seems that the leap second file isn't necessary (and that's 
> also borne out in searches) but it must provide something otherwise it 
> wouldn't exist.  The documents mention a "graceful" handling, but what 
> does that mean exactly?

The file isn't required for Windows ports of NTP, and I don't recall ever 
explicitly updating the file (if it existed) for either of my FreeBSD 
servers.  Presumably, there is output in the GPS stream signaling the 
possibility of a leap second, and/or the GPS devices produce a 61st second 
at the appropriate time.

I recall a posting somewhere showing that the different GPSs behaved in 
slightly different ways in this respect.  Last leap-second I only had one 
GPS - now I have four so it could be fun watching them argue!

Perhaps having this file would avoid such difficulties?  Where would I 
place the file for FreeBSD, and can Windows use it?


More information about the questions mailing list