Subject: Re: i386 booting, take 2
To: Phil Nelson <firstname.lastname@example.org>
From: Charles M. Hannum <email@example.com>
Date: 09/21/1998 15:49:41
> True, but we still have to deal with that old software. And aren't
> there still some machines out there that do use C/H/S addressing?
> We still should support them, if they exist.
And what does this have to do with the price of crack in Tibet? We
*do* support them. That has nothing to do with what geometry NetBSD
or the BIOS uses.
> I'd rather not have to use fdisk to find the "geometry".
Then how in the Hell do you expect it to calculate the CHS address of
the partitions correctly? It *has* to know the geometry of the disk.
(And indeed the DOS FDISK gets this information from the BIOS.) There
are a finite number of places for it to get this information from, and
we already have one (disklabel(8)) that's flexible and works.
> I assumed we were trying to make it easier for "joe average user" to
> install on a machine they have. This situation sounds much more like
> what a developer might do. At least the user would have more
> knowledge about the system than "joe average user". And yes, I agree,
> if a disk was moved from one SCSI controller to another one with
> different BIOS C/H/S parameters, you would loose if the partition
> didn't start at sector 0 or such. But that is a problem I suspect is
> not unique to NetBSD. That just shows how poor the MBR design is.
No, it shows that we need to give the user a way to change what NetBSD
thinks the geometry is -- just like the user can change the BIOS's
view of the geometry (at least for IDE/ATA disks) using the setup
program. The mechanism for doing this is disklabel(8). I simply fo
not comprehend why you want to introduce a new mechanism that people
have to learn.
> Ok, please tell me how to do the dedicated install.
That's not particularly relevant until the other known problems are
> Do you want the kernel to present these to the user at boot?
Of course not; that would be completely obnoxious. I want them to be
presented as options in the installation program's partitioning tool
-- if needed.
> So how does the install tools get all the BIOS geometries and how does
> it know which disks have been successfully matched and which one have
I didn't specify that. If I have to work out all the details, then I
might as well do it myself. (Indeed, it looks like I may have to
> I would think a simple message telling the user that the NetBSD a
> partition must be located entirely within the first X Mb of the disk
> would be sufficient. You could even put in a reference to the
> description of why this is needed. X will need to be computed
> by the install program depending on the C/H/S of the BIOS.
Great. So we confuse the user with a number that's seemingly pulled
out of the program's arse, and then say `to become unconfused, refer
to this section in the back of the manual, which hopefully you printed
out before booting the installation program'.
That's not quite my idea of user-friendly.
> We also need
> to know if we have to restrict the a partition to the first
> 1024 cylinders.
If (and only if) the boot program is unable to use `large disk'
support to get around the geometry issue.