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Hi Tobias,

* Tobias Abt <syslinux@tabt.de> [20071002 11:52]:
> The problem is that today quite a few such firmware updates do not
> fit on 1,44MB disk images and are distributed as (small) ISO images.
> Due to the number of images and the rate they are being replaced
> with new updates it would be very nice to use them as they are
> without having to convert them to HD images or something like that.

no chance. automate conversion.

Br,

Andreas

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Tobias Abt wrote:
> Hi,
>
> I looked through the documentation and the mailing list archives but
> could not yet find out whether this could be made to work.
>
> The task I want to use that feature for is being able to collect
> firmware updates for servers and their components and boot those
> updates from a notebook with DHCP/TFTP-Server. That would greatly
> reduce setup time for new server installations.
>
> The problem is that today quite a few such firmware updates do not
> fit on 1,44MB disk images and are distributed as (small) ISO images.
> Due to the number of images and the rate they are being replaced
> with new updates it would be very nice to use them as they are
> without having to convert them to HD images or something like that.
>

This is an FAQ. There exist no uniform way by which ISOs can be made
remote-bootable. Although I could write an El Torito mode for MEMDISK,
odds are very slim that it will continue working once the ISO boots,
since few if any operating systems continue to use the El Torito BIOS to
talk to the CD-ROM, and thus will find themselves confused.

It used to be that *no* operating system (including DOS) would continue
to use El Torito, but I think there is an ELTORITO.SYS for DOS now,
which would actually continue to work. The question is if anything
would actually use it.

On the latest hardware (VMX/SVM capable) one could, at least in theory,
implement a thin hypervisor and virtualize the relevant I/O ports to
make it appear that a real CD-ROM is out there. Needless to say, that's
a big effort.

-hpa

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Hello Peter,

* H. Peter Anvin <hpa@zytor.com> [20071002 19:52]:
> It used to be that *no* operating system (including DOS) would continue
> to use El Torito, but I think there is an ELTORITO.SYS for DOS now,
> which would actually continue to work. The question is if anything
> would actually use it.

.. not by itself, i.e. you'd have to touch it in any case, which makes
it a moot point again .. I wonder why companies like Dell don't deliver
PXE images like they deliver ISO and HDD images for updates and the
like. strange.

> On the latest hardware (VMX/SVM capable) one could, at least in theory,
> implement a thin hypervisor and virtualize the relevant I/O ports to
> make it appear that a real CD-ROM is out there. Needless to say, that's
> a big effort.

... and it would work on a comparatively small range of computers as
well.

Another idea I had once was some something along the lines of memdisk
installing something like a fake MSCDEX driver which uses the TCP/IP
stack left over from PXE to fetch the block requested from the CD-ROM
over the network ... most of the CD-ROM-drivers I know fail when they
encounter another driver already using the MSCDEX-name they're trying to
register themselves as - but DOS continues to boot, so the MSCDEX.EXE
might be able to use the fake CD-ROM .. you might run into memory
problems later on, and e.g. TFTP doesn't support requesting specific
blocks, so you'd have to implement something else (block ranges via
HTTP, for example, but you might have more luck extenting tftp-hpa, so
you don't need to do TCP and be really networking-interactive) ..

.. maybe feasible, but wouldn't help with linux images, or anything else
which doesn't use the (rather aged) MSCDEX ..

Br,

Andreas

--
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Andreas Kotes wrote:
>
> Another idea I had once was some something along the lines of memdisk
> installing something like a fake MSCDEX driver which uses the TCP/IP
> stack left over from PXE to fetch the block requested from the CD-ROM
> over the network ... most of the CD-ROM-drivers I know fail when they
> encounter another driver already using the MSCDEX-name they're trying to
> register themselves as - but DOS continues to boot, so the MSCDEX.EXE
> might be able to use the fake CD-ROM .. you might run into memory
> problems later on, and e.g. TFTP doesn't support requesting specific
> blocks, so you'd have to implement something else (block ranges via
> HTTP, for example, but you might have more luck extenting tftp-hpa, so
> you don't need to do TCP and be really networking-interactive) ..
>
> .. maybe feasible, but wouldn't help with linux images, or anything else
> which doesn't use the (rather aged) MSCDEX ..
>

It's not really MSCDEX that's the issue, it's the underlying .SYS
(MSCDEX talks to a DOS device driver.) If this is ELTORITO.SYS you're
okay, but El Torito didn't become common until much later. However, I
think it's available with FreeDOS, for example.

The gPXE people also have support for booting isos over iSCSI, but
exactly the same caveats apply.

-hpa

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Hi Peter,

* H. Peter Anvin <hpa@zytor.com> [20071002 21:19]:
> > Another idea I had once was some something along the lines of memdisk
> > installing something like a fake MSCDEX driver which uses the TCP/IP
> > stack left over from PXE to fetch the block requested from the CD-ROM
> > over the network ... most of the CD-ROM-drivers I know fail when they
> > encounter another driver already using the MSCDEX-name they're trying to
> > register themselves as - but DOS continues to boot, so the MSCDEX.EXE
> > might be able to use the fake CD-ROM .. you might run into memory
> > problems later on, and e.g. TFTP doesn't support requesting specific
> > blocks, so you'd have to implement something else (block ranges via
> > HTTP, for example, but you might have more luck extenting tftp-hpa, so
> > you don't need to do TCP and be really networking-interactive) ..
> >
> > .. maybe feasible, but wouldn't help with linux images, or anything else
> > which doesn't use the (rather aged) MSCDEX ..
> >
>
> It's not really MSCDEX that's the issue, it's the underlying .SYS
> (MSCDEX talks to a DOS device driver.) If this is ELTORITO.SYS you're
> okay, but El Torito didn't become common until much later. However, I
> think it's available with FreeDOS, for example.

I was thinking about getting the fake DOS device driver hooked into the
system by memdisk before DOS is started up, i.e. the driver already
being present when DOS tries to load the 'real' one ..

Unless the corresponding structures are wiped on booting, this might
stand a chance?

Br,

Andreas

--
flatline IT services - Andreas Kotes - Tailored solutions for your IT needs

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Andreas Kotes wrote:
>
> I was thinking about getting the fake DOS device driver hooked into the
> system by memdisk before DOS is started up, i.e. the driver already
> being present when DOS tries to load the 'real' one ..
>
> Unless the corresponding structures are wiped on booting, this might
> stand a chance?
>

It would have to hook into the DOS device chain, which doesn't exist yet.

-hpa

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Tobias Abt wrote:
> The problem is that today quite a few such firmware updates do not
> fit on 1,44MB disk images and are distributed as (small) ISO images.
> Due to the number of images and the rate they are being replaced
> with new updates it would be very nice to use them as they are
> without having to convert them to HD images or something like that.
>
> Thank you!
>
> Bye,
> Tobias
>
Extract the boot sector from the ISO? Typically the image is a 2.88
floppy image, which you can then load with memdisk. And to clarify,
'Typically' is the iso images that use [Free/MS/PC/etc]-DOS. Typically
is also from my experience with my vendors, so that may not work for you.

I believe you can use WinImage to do this, I think Nero can as well.
isobuster is another popular choice. Of course these are all Windows
products.

-Andrew

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Andrew Stuart wrote:
> Extract the boot sector from the ISO? Typically the image is a 2.88
> floppy image, which you can then load with memdisk. And to clarify,
> 'Typically' is the iso images that use [Free/MS/PC/etc]-DOS. Typically
> is also from my experience with my vendors, so that may not work for you.
>
> I believe you can use WinImage to do this, I think Nero can as well.
> isobuster is another popular choice. Of course these are all Windows
> products.

Yes, if the ISO is used to merely carry a disk image, then just extract
it and boot it directly with memdisk; problem solved.

-hpa

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