Date: Tue, 24 Jan 1995 04:14:09 +0000 (GMT) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: peter@bonkers.taronga.com (Peter da Silva) Cc: terry@cs.weber.edu, mmead@goof.com, hackers@FreeBSD.org Subject: Re: writing bootcode; need a method Message-ID: <199501240414.EAA08904@gndrsh.aac.dev.com> In-Reply-To: <199501232329.RAA12428@bonkers.taronga.com> from "Peter da Silva" at Jan 23, 95 05:29:39 pm
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>
> > Examining a BSD partition:
> >
> > ,---.---.----------------.----------------.
> > | 1 | 2 | 3 | 4 ... |
> > `---'---'----------------'----------------'
> >
> > 1) BSD second stage boot.
> > 2) BSD disklabel.
> > 3) BSD slice 'a'.
> > 4) BSD subsequent slices.
>
> Um, it's more like this:
>
> > ,------------------------.----------------.
> > | 3 | 4 ... |
> > |---.---. | |
> > | 1 | 2 | | |
> > `---'---'----------------'----------------'
>
> It's very important to understand that slice A contains the second stage
> boot and disklabel. I know you know that, Terry, but it's not intuitively
> obvious. In our OSF system administration class the instructor insisted
> that these were *outside* the slice and that there were special interfaces
> to get them. You need to watch out for the infamous "swap on a" problem.
Though this is true for BSD, your instructor was right about OSF/1, in
OSF/1 the vtoc, bootblocks and label live outside of the a partition:
# uname -a
OSF1 pulltime 1.2.2 osc1.2.2 b? i386
# fdisk
The data for partition 0 is:
MT
The data for partition 1 is:
MT
The data for partition 2 is:
MT
The data for partition 3 is:
systid 99, start 1, size 1094687 (534 Meg), bootid 80
beg: cyl 0/ sector 2/ head 0; end: cyl 255/ sector 255/ head 15
# vtoc
The static data for the vtoc is:
cyls 1086/ heads 16/ sectors 63; alt ptr 15360 alt len 2048
6 UNIX partition entries.
a: start 1008, end 33263, size 32256 ( 15 Meg), flag 200, tag 2
b: start 33264, end 97775, size 64512 ( 31 Meg), flag 201, tag 4
c: start 1, end 1094687, size 1094687 (534 Meg), flag 200, tag 5
d: start 97776, end 226799, size 129024 ( 63 Meg), flag 201, tag 4
e: start 226800, end 259055, size 32256 ( 15 Meg), flag 201, tag 4
f: start 259056, end 1094687, size 835632 (408 Meg), flag 201, tag 4
--
Rod Grimes rgrimes@gndrsh.aac.dev.com
Accurate Automation Company Custom computers for FreeBSD
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