Syslinux - Apr 2012 - booting a dos floppy from a disk image over pxe

Hello,
I'm trying to boot a dos floppy stored on a disk image which is initially
loaded over pxe using memdisk.
I've created the disk image as follows:

dd if=/dev/zero of=$IMGLOCATION/$IMGNAME bs=$(( 1024 * 1024 )) count=20
LOOPDEV=$(losetup --show -f $IMGLOCATION/$IMGNAME)
MAJOR_MINOR=$(ls -l $LOOPDEV|awk '{print $5$6}'|sed 's/,/:/')
DMSIZE=$(( $(ls -l $IMGLOCATION/$IMGNAME|awk '{print $5}') / 512 ))
echo 0 $DMSIZE linear $MAJOR_MINOR 0|dmsetup create hdz
fdisk /dev/mapper/hdz<<EOT
n
p
1


t
6
a
1
w
EOT
kpartx -a /dev/mapper/hdz
mkdosfs /dev/mapper/hdz1

Then I put a dosfloppy image and memdisk on the image:

mount /dev/mapper/hdz1 /mnt/
mkdir -p /mnt/boot/grub
cp dos622.IMA /mnt/boot/
cp /usr/lib/syslinux/memdisk /mnt/boot

/mnt/boot/grub/grub.cfg contains:
linux16 /boot/memdisk
initrd16 /boot/dos622.IMA
boot

and I install grub:

grub-install --root-directory=/mnt /dev/dm-0

This works perfectly on a virtualbox installation, I get a dos
environment with a C: disk.

On a live system it works till till the boot of the dos floppy. The
machine resets.

I believe it has something to do with loading a second memdisk instance
 for the floppy after the first which was used to boot the harddisk
image over pxe...

I have tried allot to get this working, even grub-legacy, but I'm out
of options...

If anyone has a idea, I would be very happy to hear!

Thanks for reading!


Regards,

Hallo, geert,

Du meintest am 02.04.12:
> I'm trying to boot a dos floppy stored on a disk image which is
> initially loaded over pxe using memdisk.
> I've created the disk image as follows:
> dd if=/dev/zero of=$IMGLOCATION/$IMGNAME bs=$(( 1024 * 1024 ))
> count=20 LOOPDEV=$(losetup --show -f $IMGLOCATION/$IMGNAME)
> MAJOR_MINOR=$(ls -l $LOOPDEV|awk '{print $5$6}'|sed
's/,/:/')
> DMSIZE=$(( $(ls -l $IMGLOCATION/$IMGNAME|awk '{print $5}') / 512 ))
> echo 0 $DMSIZE linear $MAJOR_MINOR 0|dmsetup create hdz
> fdisk /dev/mapper/hdz<<EOT
> n
> p
> 1
> t
> 6
> a
> 1
> w
> EOT
> kpartx -a /dev/mapper/hdz
> mkdosfs /dev/mapper/hdz1
> Then I put a dosfloppy image and memdisk on the image:
> mount /dev/mapper/hdz1 /mnt/
> mkdir -p /mnt/boot/grub
> cp dos622.IMA /mnt/boot/
> cp /usr/lib/syslinux/memdisk /mnt/boot
> /mnt/boot/grub/grub.cfg contains:
> linux16 /boot/memdisk
> initrd16 /boot/dos622.IMA
> boot
> and I install grub:
> grub-install --root-directory=/mnt /dev/dm-0
> This works perfectly on a virtualbox installation, I get a dos
> environment with a C: disk.
Why these circumstances?

My usual way:

Put the floppy disk into the drive

  mkdir -p /tftpboot/images
  dd if=/dev/fd0 of=/tftpboot/images/myspecial.img

for PXE-Boot:

  additional entry p.e. in "/tftpboot/pxelinux.cfg/default"

LABEL myspecial
    MENU LABEL myspecial
    kernel memdisk
    append initrd=images/myspecial.img



Viele Gruesse!
Helmut

2012/4/2 geert geurts <geert at verweggistan.eu>:
>
> On a live system it works till till the boot of the dos floppy. The
> machine resets.
>
> I believe it has something to do with loading a second memdisk instance
> ?for the floppy after the first which was used to boot the harddisk
> image over pxe...
>
> I have tried allot to get this working, even grub-legacy, but I'm out
> of options...
>
> If anyone has a idea, I would be very happy to hear!
>
Try one of the alternative memory access methods for MEMDISK:

   raw        Use raw access to protected mode memory.

   bigraw   Use raw access to protected mode memory, and leave the
                CPU in "big real" mode afterwards.

   int         Use plain INT 15h access to protected memory.  This assumes
                that anything which hooks INT 15h knows what it is doing.

   safeint   Use INT 15h access to protected memory, but invoke
                INT 15h the way it was *before* MEMDISK was loaded.
                This is the default since version 3.73.

http://www.syslinux.org/wiki/index.php/MEMDISK#Set_memory_access_method_.28raw.2C_bigraw.2C_int_.2C_safeint.29

'raw' works most of the time when the default 'safeint' fails.

- Gert Hulselmans

Hi Helmut,

The reason for this is I want to be able to have a variable sized disk
image to contain firmware images.
Just booting form a floppy of pxe is not an issue...
Thanks for your response though :)

Regards,