Re: [uml-devel] Using lilo on ubda?

[Rob Landley <rob@landley.net>]

On Saturday 26 November 2005 23:22, Andreas Wohlfeld wrote:
> On Sat, Nov 26, 2005 at 01:03:42PM -0600, Rob Landley wrote:
> > Lilo is saying that ubda is not a device with partitions.
> >
> > Anybody know what it's talking about?  (I've got a ubda1.  I'm trying to
> > make a disk image I can test boot with qemu without having to boot a
> > knoppix image to do it...)
>
> Did you use fdisk on your hard file or do you use ist as a super floppy?

I'm trying to create a partitioned image file to feed as a hard drive image to 
qemu.

I eventually made the lilo installer happy by specifying _everything_:
disk=/dev/ubda
  bios=0x80
  cylinders=128
  heads=16
  sectors=63
  partition=/dev/ubda1
    start=63

The actual booting part isn't occurring yet.  (Getting "L 99 99 99 99 99"...)  
I may have the partition offset wrong.  Run my partition finding script... 
Yup, I told sfdisk not to leave a gap here so it starts at sector 1, I 
remember now...  And now the kernel decompression is going "ran out of input 
data" because I didn't update my length hack for the new kernel I just 
built...  Forgot to make some symlinks...  Ah, I left "mknod" out of 
busybox...

Work progresses.  Slowly, as usual... :)


> Try testing it with a second hardfile and (c)fdisk it with partitions.
>
> Most of us use several hard files as super floppies not putting any
> partition table on the disk (you can see a message about that during
> boot, I think).

It's partitioned but the first partition was starting at sector 1.

#!/bin/sh
CYLINDERS=128
HEADS=16
SECTORS=63

dd if=/dev/zero of=hda.img bs=$[$HEADS*$SECTORS*512] count=$CYLINDERS
sfdisk -uS -C $CYLINDERS -H 16 -S 63  hda.img << EOF
1,$[16*63*$CYLINDERS-1],83
EOF

The old dos compatible partitions would have used a starting cylinder of 
$SECTORS instead of 1, but LILO doesn't need the gap.  (I think grub might.)

You can actually use losetup to mount a partition via -o 
$[$cylinder*$sector*$head*512] (where cylinder is actually starting cylinder 
-1, because it's how much to _skip_ and cylinder numbering starts at 1).  You 
can't feed a "length" option to losetup (only offset), but now you know what 
the blocks-count option to mke2fs is for. :)

Yes, I do this sort of thing all the time.  For fun.

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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