Re: ntp and hwclock
On Tue, 23 Jan 2007, Oleg Verych wrote:
> On Tue, Jan 23, 2007 at 03:12:45PM -0200, Henrique de Moraes Holschuh wrote:
> > On Tue, 23 Jan 2007, Ken Heard wrote:
> > > >Linux kernel updates CMOS (hardware clock) time every 11 minutes.
> >
> > Only when in ntp sync mode, AFAIK. Maybe the new RTC class lets one change
> > this easily, but then the "CMOS RTC" port to the new RTC class ain't in
> > Linux mainline yet.
>
> I think this is default, and it is not depend on new RTC subsystem,
> Try to not to run /etc/init.d/hwclock*.sh on startup, and you will see,
> that in-kernel clock is set up.
Initialize system time from RTC at bootup != sync RTC every 11 minutes.
> > Plus low stability on the kernel clock sources in the presence of cpu freq
> > changes, sleep to ram or to disk, spread-spectrum clock modulation, and general bogon activity.
>
> kernel + hardware bugs.
kernel design + hardware design + bugs in both.
> > No. On a standard consumer peecee(snort!), you will really need ntpdate to
> > be sure the clock is not set to anything dumb during system bootstrap, and
> > if you really need clock stability for real, a proper ntp setup (which is a
> > lot more than just ntpd running!) is also a requirement.
>
> I think, without bugs this is not needed, unless you need very big
> precision.
Well, I did say "if you really need clock stability for real".
--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh
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