Subject: Re: proposal for changes to todr interface
To: Garrett D'Amore <>
From: Perry E. Metzger <>
List: tech-kern
Date: 09/06/2006 21:21:17
Garrett D'Amore <> writes:
>> rc.conf is a bit late, maybe the kernel could take it directly from
>> a file (or symlink) in the root filesystem.
>> The problem with having the rtc set to localtime is that you have to
>> change the RTC_OFFSET option (at least) twice a year.
>> Doing that by modifying the bootblocks doesn't seem sensible!
> Agreed.  Windows does this by keeping track and updating when it occurs.

Well, the issue here when this got started long ago was that Windows
(senselessly) warps the clock back and forth twice a year, where Unix
(sensibly) leaves it on GMT and adjusts in userland.

Now, the rtc_offset stuff was basically just a dumb hack to make
co-existence possible, and then later we got slightly smarter and
smarter versions of it. It is, however, still an ugly hack.

The other thing to keep in mind is that you CAN'T REALLY FIX IT.

What do I mean by this?

Say you really intelligently notice the DST transition has happened
and warp rtc_offset and the clock so windows will be "happy". As soon
as you boot Windows, it will warp the clock *again*. You need to know
if you've booted Windows between NetBSD boots to know if rtc_offset
should be adjusted! And, of course, you can't know!

My suggestion is to not worry about fixing it perfectly. We can, at
best, make the kludges less ugly.