Linux Should support booting from USB harddrive.

[Donald Becker]

On Sun, 13 Oct 2002, Zou Guangxian wrote:

> i have a  usb harddrive which support booting.

Errrmm, are you certain?
The only way that a USB hard drive can support booting is if
  - it uses the same protocol as a USB floppy drive, and
  - your machine can boot off of a USB floppy drive. 

USB floppy drives has a very specific boot protocol: slightly modified SCSI
commands transported over USB frames.  It's not a particularly clean
layering, since USB has quirky semantics which impact error reporting
and command completion indications.  But nothing makes it difficult for
a hard drive to respond to require command set of a USB floppy.

The second point is more difficult.  The only machines I've seen with
USB floppy booting support have been laptops.

>so if the linux can support booting from usb harddrive ,it will be a
>good news for me .:) 

Linux can support it, and we've built bootable floppies for the Scyld
system that do it.  The key idea is to put the USB support on an initial
ramdisk.  The only complication is that the "hotplug" support keeps
getting more complicated and you might difficultly fitting the current
code on the floppy.

-- 
Donald Becker				becker at scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993