[ntp:questions] ntpd -x and leap seconds

Mike Cook michael.cook at sfr.fr
Mon Feb 9 13:58:29 UTC 2015


As the man page for ntpd does not specifically exclude leap second ‘stepping’ from the -x behavior, I think that it could well be that the behavior that you describe is a bug. That said, it would be nice to have a  -x [ policy ] option for it, with the type of slewing for the leaping day ;-) . Could be [ linear | google | step | custom ].


> Le 9 févr. 2015 à 11:49, Miroslav Lichvar <mlichvar at redhat.com> a écrit :
> 
> I was wondering what others think about handling leap seconds when
> ntpd is running in the "slew only" mode (-x option).
> 
> The -x option disables the kernel discipline, so the kernel is not
> told about pending leap seconds and its up to ntpd to do whatever is
> needed. Older ntpd versions (before 4.2.6) didn't handle leap second
> in the daemon loop and -x could be used to avoid the backward step in
> the Unix time scale and possibly upset the applications running on the
> system.
> 
> In 4.2.6 was added support for leap seconds in the daemon loop and
> ntpd now steps the clock by calling settimeofday() or clock_settime(),
> even if the step threshold (set by -x or tinker step) is larger than
> one second.
> 
> Should be leap seconds threated as a normal offset and not corrected
> by step when the threshold is larger than 1.0? Should there be a
> separate option for them?
> 
> http://bugs.ntp.org/show_bug.cgi?id=2745
> 
> -- 
> Miroslav Lichvar
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