[syslinux] Changing USB-key geometry from syslinux.exe?

[H. Peter Anvin]

Paolo Salvan wrote:
> I'm playing with syslinux 3.0x to get PC to boot from USB key...
> 
> In particular, I'm giving a look at the "ZIP geometry hack" to get some more
> BIOS boot working with USB...
> 
> Some question:
> - if we have a usbkey with a single partition, can we change the geometry
> without requiring to reformat the partition? Or is a reformat unavoidable?

You can do it by poking the FAT header (and probably the partition 
table, although SYSLINUX and the SYSLINUX MBR ignores the CHS 
information in the partition table.)

> - at the moment we can use the "ZIP geometry hack" only under linux...with
> extlinux or mkdiskimage; will we be able to use it under windows also?
> 
> More specifically:
> 
> - extlinux support a nice "--zip" option to emulate the usb-zip geometry, will
> we get this option on syslinux.exe/syslinux.com also?

Hmm... syslinux.exe/syslinux.com expects an already formatted 
filesystem, and doesn't change the formatting.  The best would be if you 
could specify this at formatting time.  It might be doable to add that, 
though, but I can't promise when.

> Does this option also
> change the active partition number from 1 to 4?

No.  Shouldn't matter though.

> Well, obviously my dream is to use syslinux as a simple way to get a
> fat-formatted usb-key bootable, with best compatibility with bugged bioses...
> And having all this usable also from windows PCs... ;o)

Tough order...

	-hpa