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Re: Multiple boot from USB stick

From: Karsten Malcher
Subject: Re: Multiple boot from USB stick
Date: Tue, 16 Feb 2016 12:29:30 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.5.0

I think we are talking at cross purposes.

>> O.K. This is clear now.
>> One more interesting thing. When you use
>> you can get here:
>> But for me still is not clear where you get the memdisk.iso and fdbase.iso ?
> There is no memdisk.iso. memdisk was from Sylinux installed on my
> Linux. fdbase was a typo, it is whatever I downloaded from freedos.og.
> freebasecd.iso.

I should clean my glasses. :-)
Indeed i read memdisk.iso instead of memdisk iso.

Just doing it correct it is working.

>>>> Why you can boot them without a loopback?
>>> Because no loopback is needed. I want to boot from ISO, not extract
>>> files from it.
>> I thought grub must use loopback to access the kernel to boot within an iso 
>> file?
> If you want to load file that is located inside ISO image, then you
> need loopback. I did *not* need any file from ISO image.

O.K. Then memdisk "knows" automatically where it must search for the kernel and 
boot it.
Sorry that i did not read the description about memdisk exactly.

Add the following in your config scripts for grub2:

 menuentry "Boot Hardware Detection Tool from floppy" {
   linux16 /memdisk
   initrd16 /hdt.img

 menuentry "Boot Hardware Detection Tool from iso" {
   linux16 /memdisk iso
   initrd16 /hdt.iso

 menuentry "Boot DOS from floppy image (with 'raw' parameter)" {
   linux16 /memdisk raw
   initrd16 /dosboot.img

>>> I do not know what fdboot.img does so I cannot comment.
>> This is the kernel image of freedos within the iso file.
> Does it explain anything?

Yes - that i thought that i must explicit name the kernel file that have to be 
loaded to boot.

>> I think there are parts of your grub.cfg missing.
> I do not have any grub.cfg. You do not need it to execute three commands.

O.K. I didn't know that.
Of course i don't want to remember and type this commands.
I just want to insert the USB stick and then choose in grub what i want to boot.

This will work:

search --no-floppy --fs-uuid --set=root C8B1-D774
set lang=de

menuentry "FreeDOS ISO Image with memdisk" {
        linux16 /boot/img/memdisk iso
        initrd16 /boot/iso/fdbasecd.iso

>> The role of memdisk is still not clear for me.
> It provides emulated device accessible via BIOS calls. It also has a
> bit more intelligence, e.g. it knows how to extract and launch boot
> image from bootable ISO.

Thanks - i have checked the missing details to understand now.

>> But it does what i expected from it:
>> Freedos can't access the files within the iso, because the iso file is not 
>> "mounted as cdrom".
>> I have no idea how to do the trick?
> Why do not you simply try what I suggested? Or if you insist on doing
> it using grub.cfg and loopback ...
> menuentry "FreeDOS ISO Image Isolinux" {
>         set isofile="/boot/iso/FreeDOS_1.1.iso"
>         loopback loop (hd0,1)$isofile
>         linux16 (loop)/ISOLINUX/MEMDISK iso
>         initrd16 (hd0,1)$isofile
> }

I just insist to use grub.cfg. :-)
But of course it is working too, when i type it into the grub console.

The diffedence between memtest and loopback is clear now.
Thank you!

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