CMOS, daylight saving time and dual-boot

[Eugene Grosbein]

Doug Barton wrote:

> > Suppose, the machine does not have global connectivity at all
> > (and it has no local source of exact time) or just at the boot time.
> > It still needs to adjust local time, right?
> 
> Your post posited a problem with ntpd not being able to synch the time
> because it was an hour off. The fact that the DST problem caused the ntp
> problem isn't really relevant.
> 
> > It seems to me as DST problem really, not NTP problem.
> 
> I don't think I properly stated my actual point, which is that the issue
> you're describing is an edge case, and we have about 1k more important
> things that need developer time.
> 
> If you choose to spend some of your time fixing this problem I'm sure we'd
> all be interested in your results.

I did some investigations about the issue. It seems there are two things
to be done to fix this:

1) Choose a place to keep DST flag that was actual at the moment
of last shutdown. It may be CMOS bit or on-disk file. On-disk file
is less suitable for diskless stations but they can't run Windows anyway
and should keep its CMOS times in UTC. OTOH, CMOS flag may be shared
between several OS'es.

2) Teach 'adjkerntz -i' to respect the flag whenever it resides
and adjust machdep.adjkerntz as needed.

Both tasks are pretty simple and require just an accurate implementation.
I'll try to find time for this.

Eugene Grosbein