Re: Booting from USB HDD without BIOS support

From: Tauno Voipio (tauno.voipio_at_iki.fi.NOSPAM.invalid)
Date: 06/14/05 

Date: Tue, 14 Jun 2005 06:59:43 GMT

Stephan Keil wrote:
>>> I suppose it is possible to setup e.g. a small boot CD (booting from
>>> CD is supported), which loads a USB driver and finally boots Linux
>>> from the USB harddisk.
>
>
>> The bootable CD contains a floppy image (usually 2.88.Mbytes)
>> which is shown as a floppy to the BIOS during booting.
>>
>> So, you need a floppy image that contains the required drivers and
>> is bootable (first 512 bytes read via int 0x13 to 0x7c00 and
>> started up at the first byte).
>>
>> For details, Google for 'El Torito Specification'.
>>
>> The Linux mkisofs utility can insert the boot diskette image
>> into a CD file system image.
>
>
> Hm, sounds like a lot of low-level work :-o.
> My approach was more like installing a Linux kernel with builtin
> USB-drivers on the CD. But actually I would prefer to not install my
> "production kernel" on the CD but some kind of "boot only" kernel. Is it
> possible to "swap" the kernel after booting?

There's no easy way - the kernel runs in 32 bit mode and the
booting runs in 16 bit (real) mode. You'd need to do some serious
kernel hacking to return to the real mode.

If you can get a version of GRUB able to boot your disk,
a floppy with that GRUB diskette image might be the solution. 

-- 
Tauno Voipio
tauno voipio (at) iki fi

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