Re: Boot windows on external disk : "not a valid root device"

[Colin Watson]

On Wed, Jan 02, 2013 at 12:31:14AM +0100, Hervé Guillemet wrote:
> I have a new Asus N56VZ laptop and replaced the Windows hard drive by a
> SSD with Linux installed. EFI Grub2 successfully launchs Linux.
> Now I'd like to boot Windows from the original hard drive mounted by USB.
> 
> No matter what I try, either using grub.cfg or command line, Grub's
> chainloader fails :
> 
> > set root=(usb0,gpt1)
> > chainloader ($root)/EFI/Microsoft/Boot/bootmgfw.efi
> Error: not a valid root device.
> 
> The content of the drive may be seen using "ls".
> 
> What's the exact meaning of "not a valid root device" ?

It indicates that either no UEFI device handle corresponding to that
device was found, or that no UEFI protocol interface is available for
that device handle.  In other words, "can't work out how to talk to that
device using UEFI".

I think your device naming is dubious: as far as I can see, GRUB's
efidisk module does not fully support calling a disk "usb0".  The "ls"
command should show you the list of available disks and partitions, or
you can type "set root=(" and then use tab-completion.  If the disk is
truly only accessible as "usb0", then perhaps efidisk needs some work to
support that.

-- 
Colin Watson                                       address@hidden