Re: bootxx needs to fit within 0th track of MBR partition?

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> I'm fairly sure that, yes, the distance from "beginning of drive" to
>> "beginning of UFS" is 8K for UFS1, assuming of course that there is
>> a filesystem partition starting at start-of-disk.  With one sector
>> occupied by MBR and label, that left 7.5K for the bootblocks.
> one each, so 14s = 7K?

Teal deer: 7K, but for slightly different reasons.

There's 8K of space not used by UFS1 - that is, the filesystem doesn't
care what's in the first 8K of its partition.  On i386 and amd64, my
experience is that the MBR is in (absolute) sector zero, the first MBR
partition does not begin at offset 0 (usually offset 8 or 63, in my
experience), and the space between sector zero and the start of the
first MBR partition is unused.  The boot partition then has a PBR in
(partition-relative) sector zero and a label in sector 1.  Sectors 2
through 7 are available for bootblocks, hence 7K, but at a different
place.

I have a fuzzy memory of using an MBR partition beginning at offset
zero, but I can't recall what for.  It might not have been a bootable
disk, in which case most of this discussion is irrelevant.

I suspect CHS addressing may complicate this some.  My grasp of how CHS
addressing works is fuzzy at best; the above is almost entirely about
LBA-addressed disks, or CHS well-behaved enough to think of it as LBA
in a funny variable-radix representation.

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