Re: REMINDER: LEAP SECOND

[Matthew Huff <mhuff () ox com>]

A backward step is a known issue and something that people are more comfortable dealing with as it can happen on any 
machine with a noisy clock crystal.

Having 61 seconds in a minute or 86401 seconds in a day is a different story.

> On Jun 23, 2015, at 8:37 PM, Harlan Stenn <stenn () ntp org> wrote:
>
> shawn wilson writes:
> > On Jun 23, 2015 6:26 AM, "Nick Hilliard" <nick () foobar org> wrote:
> > >
> >
> > > Blocking NTP at the NTP edge will probably work fine for most situations.
> > > Bear in mind that your NTP edge is not necessarily the same as your
> > network
> > > edge.  E.g. you might have internal GPS / radio sources which could
> > > unexpectedly inject the leap second.  The larger the network, the more
> > > likely this is to happen.  Most organisations have network fossils and ntp
> > > is an excellent source of these.  I.e. systems which work away for years
> > > without any problems before one day accidentally triggering meltdown
> > > because some developer didn't understand the subtleties of clock
> > monotonicity.
> > >
> >
> > NTP causes jumps - not skews, right?
>
> Left to its default condition, ntp will step/jump a change in excess of
> 128msec.
>
> If you want to slew the clock instead, a 1 second correction will take a
> little over 33 minutes' time to apply.
>
> I don't understand why people believe that stopping ntpd for a few
> minutes while the leap second is applied will help.  If the system clock
> keeps good time, it will *still* be about 1 second ahead when ntpd is
> restarted, and that will trigger a backward step which is fatal to a
> number of applications.
>
> H