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

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 02.01.2013 02:05, Hervé Guillemet wrote:

> Le 02/01/2013 01:33, Vladimir 'φ-coder/phcoder' Serbinenko a écrit :
>> On 02.01.2013 01:14, Colin Watson wrote:
>>
>>> 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.
>>>
>>
>> Other than loopback, all devices follow the naming scheme insluding type
>> prefix as detailed in manual. "usbN" means that the device is accessed
>> using GRUB own modules. To use chainloader on EFI you have to avoid
>> loading any USB modules and use hdX names.
> 
> Ok, I tried, but then the external disk is not visible and ls only shows
> me hd0. Can you see a possible solution ?
> 

It probably means that EFI doesn't see you USB disk. Be sure that it's
connected on poweron and be sure to use recent GRUB. If still doesn't
help look if it's seen through EFI shell.
For using chainloader you need disk to be visible through EFI, otherwise
bootmgfw.ef won't be able to find rest of the files.
If the EFI doesn't see the USB disk in shell and/or in boot device
selection you should contact your manufacturer.

> 



-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko

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