[syslinux] Booting ISO images over PXE

H. Peter Anvin hpa at zytor.com
Tue Oct 2 12:11:04 PDT 2007

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.


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