[syslinux] Syslinux/isolinux: is this possible?

[H. Peter Anvin]

Jonathan Woithe wrote:
> Hello Peter
> 
> I know very little (currently) about the BIOS interfaces/APIs available at
> boot time except that most of them are buggy to some extent.  However, I
> have had an idea regarding another way to boot Linux and wanted to run it
> past you.
> 
> As you'd be aware, many of the distributions now require multiple floppies
> to hold their initial root fs to be used during installation.  I was
> wondering whether it would be possible to make isolinux/syslinux boot from a
> floppy but then access an initial ramdisk from a (possibly fixed) location
> on a CD.  This way one can get around buggy bioses which refuse to boot from
> a CD, but you don't have the inconvenience of 4 or 6 floppies when loading
> that initial ramdisk.
> 
> This may be completely impossible - that's fine.  However, I thought it best
> to run it past the expert in these matters before trying to do something
> myself which would turn out to be impossible.
> 

It's not possible... at least not in the way you want to do it.  The 
reason is that the BIOS doesn't provide any kind of driver for the 
CD-ROM (or the network, for that matter) *unless* it's the boot medium. 
  Therefore, the boot medium is the *only* medium you get before you 
have to become "self-sufficient" -- meaning you have to carry your own 
drivers with you.  This means you have to have drivers for every 
possible way to connect CD-ROMs... IDE, USB, and all kinds of SCSI 
controllers... not to mention proprietary interfaces.

You might be able to use a single-floppy-sized Linux kernel for this 
purpose, mount the CD as root, and then use modules or something like 
Two Kernel Monte to load any other drivers you need.  Otherwise you're 
going to have to do an awful lot of work.

	-hpa