[syslinux] USB question

Nazo nazosan at gmail.com
Wed Apr 12 13:36:58 PDT 2006

On 4/12/06, Rich Mahn <rich at lat.com> wrote:
> The BIOS on my laptop does not support booting from USB.
> I would like to be able to have my Windows XP on a partition
> on a USB disk drive and be able to run from the USB disk using
> perhaps a CD or floppy to bootstrap the system.
> My questions:
>   1). Is there a way to use syslinux and friends to do this?
>   2). If not, is there some other boot loader that may work?
>   3). Is there any hope at all?
> Rich
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1.  Syslinux relies on the BIOS to handle actually accessing the
USB/etc.  I can't imagine any way in which it could manage to do what
the BIOS can't in this particular respect.

2.  I'm pretty sure they all have the same problem.  However, some
like Lilo us a lot of the linux stuff from the system you actually
install on.  I don't know what would happen if you tried to trick it
into working somehow, but, who knows, maybe it's worth a go?

3.  Well, there's another more indirect way that some do, especially
with live boot discs.  They load up a kernel + initrd with USB support
and then proceed to mount USB drives looking for the rest of their
data.  Almost all live distros that support booting from a USB drive
at all do it this way I think.  I know all the ones I've used do. 
It's pretty tough to do this with a floppy.  You usually have to split
it up with the kernel on one disc and the initrd on another.  I never
studied how this was done since back then I didn't use linux much and
today I can't even retain a functional floppy drive more than a few
weeks before it tears up.  HOWEVER, I suspect the way this is done is
it first loads an absolutely minimal ramdrive with nothing extra but
support for /dev/fd0 and a simple init script which loads up a real
ramdrive from the next floppy.  If you use a CD this should be easy to
do via the live distro method since space isn't an issue.  However, if
you're going to use a CD, what you should probably do is set it up so
that it only uses the USB drive for things that change who's changes
you need to retain across reboots.  No need to throw the entire
filesystem on there after all.

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