Re: chained grub2 derivative bootauto system

["Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@gmail.com>]

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On 01.09.2012 08:06, Brendan Trotter wrote:

> Hi,
> 
> On Fri, Aug 31, 2012 at 11:59 PM, Lennart Sorensen
> <lsorense@csclub.uwaterloo.ca> wrote:
>> On Fri, Aug 31, 2012 at 09:19:43AM +1000, Philip Rhoades wrote:
>>> Ivo,
>>>
>>> Interesting idea - I particularly like the idea of booting from
>>> arbitrary isos.
>>
>> Too bad that accessing an iso on a usb key is nothing like an actual cd
>> or dvd and the sytem you boot must have support for the fact you put the
>> iso on the usb key rather than as a real disc.  Nothing the boot loader
>> can do to change that.
>>
>> If it was really that simple, someone would already have made such a
>> boot loader for use on usb keys.  The reason it doesn't exist yet is
>> that it can't exist.
> 
> For "PC BIOS", having a USB with multiple ISO images would actually be
> relatively easy.
> 
> The USB's boot code would need to hook Int 0x15 to steal some memory,
> then install code that emulates a CD (and El Torito) into the stolen memory.
> Obviously you'd also hook "Int 0x13" so that the BIOS disk services are
> redirected to your CD emulation code.
> 
> I'd expect that similar would be possible for UEFI (e.g. create a special
> UEFI driver that emulates CD/s).
> 
> The main problem is after the OS on the ISO tries to take control of hardware
> and fails to find its (emulated) CD. For some OSs this may not be a problem -
> e.g. MS-DOS and FreeDOS (which continue to use the BIOS services
> and don't take control of hardware), Linux (as long as the root
> partition isn't on
> the emulated CD), etc. For other OS's (Windows) it can't work.
> 
> However, someone that wants to create a USB like this might not care about
> those "unsupportable" OSs anyway.
> 
> Finally; I'm not sure how a scheme like this would involve GRUB - you'd want
> relatively specialised USB boot code (not GRUB). GRUB could (potentially)
> be installed inside one or more of the ISOs, but this would be a normal
> "El Torito" (or UEFI) boot as far as GRUB would know.
> 

This is something that can be included in GRUB. Just the amount of
needed work isn't comparable with the number of additional scenarios
supported (namely mostly only *DOS on ISO).

> 
> Cheers,
> 
> Brendan
> 
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> 



-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko


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