Mailinglist Archive: opensuse-factory (845 mails)

["Carlos E. R." <robin.listas@xxxxxxxxxxxxxx>]

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The Sunday 2008-05-11 at 10:17 +1200, Volker Kuhlmann wrote:

> On Sun 11 May 2008 01:04:01 NZST +1200, Carlos E. R. wrote:
>
> > > Both are multiboot systems with the hardware clock set to local (GMT-0400)
> > > time. Why are they different?
>
> I've observed cmos clock drifts of 3s/day on recent motherboards,

Those are the ones adjusted by adjtime. The thing is that the drift, as 
for any standalone digital quarttz controlled clock, is fairly stable, and 
thus, adjustable.

It is not a problem if they have 5 second drift. It is if it varies.

> and
> wouldn't put much mnore faith into CPU clock frequency accuracies either
> (which is what the kernel time runs on while the computer is running).

Right.


> > different drifts.
>
> > cer@nimrodel:~> cat /otros/test_d/etc/adjtime
>
> And each of them assumes it's the only one writing to cmos and therefore
> being able to measure its clock drift.

right.

And all are wrong because there have been other adjustements.

> Even with a single-boot system I
> didn't get high confidence in the past of this process working realibly.

It does, fairly well. It is the cpu clock which is very unreliable nowdays.

> Just through adjtime away completely and fetch the time (ntpdate) when
> booting. Run ntp on anything turned on more than a day if you care about
> the time, run ntp *always* on networked computers that may run several
> days at once.

Adjtime is quite ok, and ntp is better if you can use it. If you don't 
have network, it worked fine. Nowdays, i have my doubts.

- -- 
Cheers,
       Carlos E. R.

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