Re: Windows multiboot (aaargh!)

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To: debian-user@lists.debian.org
Date: Sat, 13 Sep 2003 16:33:22 +1200

On Thursday 11 September 2003 09:38, Pigeon wrote:

(preliminaries snipped)

OK, I'm aiming for

> 1 Pri DOS 500MB Bootable ; for DOS
> 2 Pri DOS 600MB ; for W95
> 3 Pri DOS 600MB ; for W98
> 4 Extended --> 5 DOS 500MB ; DOS "optional"
> \-> 6 ext2 800MB ; Linux

as you suggested. This is kind of a progress report with a heap of
supplementary questions that have arisen. If it all works maybe I should
make a HOWTO out of it (since there seem to be a couple of points that the
existing HOWTOs don't specifically cover).

> The selection between which Microsoft OS you want to boot involves a
> bit of kludgery to set up and a bit of kludgery to use. This is what
> I'd do:
>
> To set up:
>
> - Make a DOS boot floppy with FDISK and FORMAT on, and a Linux boot
> floppy with cfdisk on.

I made the DOS floppy some time ago, with handy utilities plus MSCDEX and a
generic CD driver.

The Linux boot floppy is a bit more tricky. I thought I'd better first
delete the existing Linux partitons on the drive using cfdisk rather than DOS
fdisk. So I tried adding cfdisk to a spare Debian Woody boot floppy, but it
got 'kernel panic' when run. Tried same with a RH boot floppy and it
worked OK (I think the hard drive had RH7.3 on it, IIRC), but got 'kernel
panic' when I used it after wiping the hard drive. Obviously Deb and RH
boot floppies are just intended for booting the system on the hard drive.

I tried Googling for how to create a boot floppy, what I found was several
rescue disks - Tomsrtbt, RIP and Leka - all of which downloaded quite nicely,
installed themselves onto floppies exactly as per instructions, and work very
well. They all have fdisk (but not cfdisk). I can recommend them to
anyone reading this, as a useful tool to keep handy. But as they're so
compressed I can't put anything extra on them. I suppose I could put cfdisk
on another floppy and run it from that after Toms/RIP/Leka are running
in RAM.

> - Boot DOS, and partition /dev/hdc with one 500MB primary DOS
> partition (for your DOS boot partition), no other partitions.
> - Boot Linux, and use cfdisk to change the partition type of that
> partition to something DOS doesn't recognise.

As a matter of interest, fdisk doesn't have 'DOS' or 'ext2' in its list of
filetypes - I assume 'FAT16' and 'Linux' are the equivalents.

> - Boot DOS, and add a 600MB primary DOS partition for your Win95 boot
> partition.
> - Boot Linux, and use cfdisk to change the partition type of the new
> partition to something DOS doesn't recognise.
> - Boot DOS, and add a 600MB primary DOS partition for your Win98 boot
> drive. (You can convert it to FAT32 later from within Win98.) Then
> add an extended partition and create your "optional" 500MB DOS
> partition inside it.
> - Boot Linux, and add your 800MB ext2 partition in the extended
> partition. Then change the partition types of the first two
> partitions back to primary DOS. Set the "bootable" flag on one of
> them.

So far so good....

> - Boot DOS, and FORMAT /U /S all the DOS partitions.

Oops. Unexpected problem. What I had so far was:

 1 Pri DOS 500MB Bootable ; for DOS "Kludge1"
 2 Pri DOS 600MB ; for W95 "Kludge2"
 3 Pri DOS 600MB ; for W98 "Kludge3"
 4 Extended --> 5 DOS 500MB ; DOS "optional" "Kludge4"
             \-> 6 ext2 800MB ; Linux

(The volume names are just arbitrary for ID purposes)

DOS formatted partition 1, and later 3 and 4, okay, but on partition 2
it got 63% through then started "Trying to recover allocation unit 245xx" and
counting... I let it count all the way to 33xxx before I hit Ctrl-C.

It did exactly the same on a second attempt, same place. Of course DOS
scandisk wouldn't work on that partition. So I used my floppy Linux fdisk
to change it to ext2 and ran mke2fs and e2fsck -cnv - which found
nothing wrong. (And the 3GB drive worked fine with RH7.3 on my previous
install). So I changed it back to DOS, ran DOS format again - same problem
exactly.

(Incidentally, as a mild curiosity, DOS fdisk now shows my drives as this:

C: 1 PRI DOS A Kludge1 500 FAT16
E: 2 PRI DOS Kludge3 602 FAT16
F: 3 PRI DOS 602 FAT16
      4 EXT DOS 1378

.. and the extended partition shows up as
D: Kludge4 500 FAT16

The odd thing is that fdisk shows the as-yet-unnamed Kludge2 and Kludge3 as
*swapped*. This is WRONG. 'dir' says that drive F: is Kludge3, and E:
just gives a "Invalid media type reading drive E" - which is as it should
be since I can't format it.
I suppose this is some odd consequence of the weird way DOS numbers
partitions, but fdisk and COMMAND.COM obviously implement it differently.)

Anyway, the glitch that DOS hits (and Linux doesn't) appears to be at around
879MB from the start of the physical drive, if I believe Format's "63%"
figure. Only fix I can see is to make it a Linux partition. I think
this means fitting three DOS/Win partitions in before that, (if I want them
to be primary and hence bootable), which would make them very small indeed.

Some thought is indicated. I may save this drive for Linux use (with which
it works fine) and pick up another drive for my experiments.

>
> To switch between booting different OSes, two methods are possible:
>
> - (Easy, but unsmooth) Use Norton Utilities (for DOS) to edit the
> partition table and set the "bootable" flag on the partition for the
> OS you want to boot. From within Win95/98, set the shortcut to
> Norton to "run in MS-DOS mode".
> - (Not so easy, but smoother) write a program to set the appropriate
> "bootable" flag as you instruct and then reboot. For example, you
> could have it accept as a command-line parameter the OS you want to
> switch to, and then "reboot 95" or "reboot 98" from within DOS, or
> in 95/98 set a couple of shortcuts with the appropriate command-line
> parameter and "run in MS-DOS mode".

Or, could I just use Linux fdisk?

(much snippage)

> It is also possible to boot Linux from within DOS/Windoze using
> LOADLIN.EXE (again "run in MS-DOS mode") without actually rebooting.

I was thinking of trying that later, though I was unsure about how stable it
might be. But quite by chance, I found that the install for the DOS zip
version of Tom's Root Boot does exactly that - when unzipped (in DOS),
running 'install.bat' immediately uses loadlin to start its own little Linux
system to create the floppy. And it *all*, Linux system plus floppy
contents plus HTML faq, comes in a 2.2MB zip file. Tom must be a fanatic
at squeezing the maximum stuff into the tiniest package.

cr

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• Previous message: Dan Jacobson: "just get the changelog"
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