On Thursday 06 January 2011, Dale wrote:
> Francesco Talamona wrote:
> > On Wednesday 05 January 2011, Dale wrote:
> >> Now on my old system, it would adjust the drift file and the
> >> adjustments would get smaller and smaller. On the new rig, as
> >> you can see it stays about the same. I would like it to get to a
> >> point where it doesn't have to sync so often. I read on the
> >> website where they are needing more servers to help with the load
> >> and I don't want to be one of the ones putting a load on it.
> >
> > Maybe you copied over /etc/adjtime from the previous machine. I
> > would try to regenerate it...
> >
> > Ciao
> >
> > Francesco
>
> I'm sure I didn't copy that. I copied ntp.conf but that is all. I
> didn't even notice that one being there. I got to see what purpose
> that has.
>
> I may delete it tho and see what happens. It would generate a new
> one if I restart the service correct?
>
> Dale
>
> :-) :-)
It makes the hardware clock take care of the systematic drift. If a
wrong value is stored in it, it can interfere with ntp in the way you
described: every time ntp runs it always corrects for the same amount.
From man 8 hwclock:
"The Hardware Clock is usually not very accurate. However, much of
its inaccuracy is completely predictable - it gains or loses the same
amount of time every day.
This is called systematic drift. hwclock's "adjust" function
lets you make systematic corrections to correct the systematic drift."
and:
"It is good to do a hwclock --adjust just before the hwclock --hctosys
at system startup time, and maybe periodically while the system is
running via cron."
This is my "recipe":
let ntpdate sync your clock, then /sbin/hwclock --systohc
and you are done. From that moment on ntp takes care of the non
systematic error, while the drift is zeroed "by hwclock".
Somewhere it is suggested to run /sbin/hwclock --adjust once a year.
I experienced what you describe when I built my new machine, I had
copied /etc/adjtime (without knowing what it was) from the previous, it
took me a good deal of googling...
BTW I don't have ntp.drift, I only use ntpdate and the clock is always
correct.
HTH
Francesco
--
Linux Version 2.6.36-gentoo-r6, Compiled #2 SMP PREEMPT Mon Jan 3
11:54:58 CET 2011
Two 1GHz AMD Athlon 64 Processors, 4GB RAM, 4021.84 Bogomips Total
aemaeth
