booting from usb pen drive

[Donald Becker]

On Sat, 22 Nov 2003, Mark Hahn wrote:

> > Depends if your mobo has a boot from usb option.

It's slightly more complex than that: only some (many, but not all) USB
memory devices are usable as boot media.

The Intel-branded Itanium-2 (I2) machines can boot from USB devices.
Intel might be the best source for a list of usable USB boot devices.

The I2 might be the only interesting case for USB booting: an I2 kernel
can't even come close to fitting in 1.44 or 2.88 MB!

> I wonder how bootable usb-keys work.  it would be pretty useless
> if the bios only had enough smarts to load a bootsector and run it.
> the bios must at least contain enough of a usb-block driver to let
> it emulate a floppy disk.  if so, I'd expect linux to "just work"...

We've been doing this for years with Scyld BeoBoot: use the BIOS to load
both the kernel and an ramdisk '/'.  The now-standard Linux approach is
loading an "initrd", which accomplishes the same thing with a slightly
different environment.

The advantage here is that the kernel doesn't require USB support
built-in, or any USB support at all!  Everything needed from the boot
media is loaded into memory by the boot ROM + BIOS.

But bottom line is that booting is no longer a hotly-debated cluster
issue.  Essentially every current system has PXE network booting.
Approaches such as BeoBoot stage 1 or USB booting are only needed for
legacy machines.  With x86 machines you can use PXE to do BIOS
updates, hardware diagnostics, or boot the machine as a cluster node,
all without touching the hardware.

-- 
Donald Becker				becker at scyld.com
Scyld Computing Corporation		http://www.scyld.com
914 Bay Ridge Road, Suite 220		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993

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