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Re: drivemap and uefi

From: Andrey Borzenkov
Subject: Re: drivemap and uefi
Date: Sat, 10 May 2014 22:42:01 +0400

On Sat, May 10, 2014 at 4:27 AM, Francisco Franchetti <address@hidden> wrote:
> Thanks for the clarification.
> I solved my problem so this is just in case you are curious. I am used to
> mbr and in that context it's important to start the windows installers as
> follows: the disk to which one will install windows, which will remain in
> the computer after the install is gone, has to be hd0; the installer is in
> another (usb) disk that must be interpreted as being at hd1; however, most
> bios will set the booting device to hd0, so using grub I usually flip the
> order with map; in a nutshell this allows for the computer to boot properly
> after one has installed windows; there are other workarounds equivalent to
> update-grub in windows with the boot.ini but what I described is my
> preferred way of doing it and I don't have for the future a great way to
> deal with the problem. Will the problem not exist under uefi/win8?

I can't say how Windows will react to moving drive to different
physical path, sorry. Never tried it and I do not have any UEFI based
systems where I can test it.

> What I did was, since the disk with the win files was not gpt, and I had no
> flash drive of the appropriate size, I created a gpt partition at the end of
> the destination disk, then booted grub from the ubuntu installer,
> chainloaded to the gpt partition with the files, and the installer started
> and worked fine. But the point of this second paragraph is: the only disk
> was the destination one. If I had a gpt partitioned usb disk, I am not sure
> if the installer would like it to be sitting there in the hd0 position while
> installing, pushing the destination disk to hd1 during installf, but later
> becoming hd0. I don't know enough about uefi/win8 to know; I'll experiment
> in the future with that. For now, I'm out of the woods.
> Anyway, the most important aspect of the email is to say thank you for
> clarifying that drivemap is an mbr specific command.
> On Fri, May 9, 2014 at 3:09 PM, Andrey Borzenkov <address@hidden>
> wrote:
>> On Wed, May 7, 2014 at 9:36 PM, Francisco Franchetti <address@hidden>
>> wrote:
>> > I am not sure if the absence of the drivemap command is due to uefi mode
>> > booting or if it is due to the version of grub 2 that I have:
>> > 2.02beta2-9
>> > from ubuntu installer.
>> >
>> > Anyone knows why the drivemap command is unavailable? Is it because on a
>> > normal uefi system the notion is irrelevant?
>> >
>> Yes. drivemap manipulates BIOS drive numbers via BIOS entry points.
>> Neither exists in case of UEFI.
>> > I am interested in the knowledge and the drivemap command in itself, but
>> > the
>> > practical application is to boot a win 8 installer and have the hd0 be
>> > the
>> > computer installer, which is showing as hd1 because hd0 is taken by the
>> > usb
>> > installer.
>> I'm not sure I understand the problem. Could you explain it in more
>> details?
>> ________________________
>> > Help-grub mailing list
>> > address@hidden
>> >
>> >

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