Bug#289267: [pkg-ntp-maintainers] Re: Debian #289267: ntpdate should use ifupdown instead of rcS to start

Kurt Roeckx kurt at roeckx.be
Mon Jan 8 18:37:16 CET 2007

On Mon, Jan 08, 2007 at 04:03:23PM +0000, Scott James Remnant wrote:
> On Fri, 2006-12-15 at 15:18 +0100, Tore Anderson wrote:
> > * Scott James Remnant
> > 
> > > I'd actually argue that you wouldn't want to forcibly change the clock
> > > once the first service is *starting*.  As soon as you have at least one
> > > service running, it's arguably dangerous to slew the clock, and instead
> > > we should always step it from there on.
> > 
> >   Say what?!  I hope you've just mixed up the terms here...
> > 
> >     "slew" -> adjtime() -> safe, clock will never leap
> >     "step" -> settimeofday() -> unsafe, clock will leap [back in time]
> > 
> >   I'll read the rest of your email assuming you exchanged those two.
> > 
> It's entirely probable ;-)  Step to me implies taking small steps,
> whereas slew implies sliding the clock the entire way.
> Not the most unambiguous of terms <g>

Step is as directly changing the time to the new value.  If you put "time"
into the function of "time", you'll see a jump/step in it.  This also means
that time can suddenly go back.

Slew means that it'll change the frequentie at which the clock changes
it changed until the offset is gone.  Now if you put time in function of
time, the direction of the curve changes for some time, and then gets
back to normal.  There are no jumps/step in the curves, and nothing
should see that the time was actually changed.


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