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Re: drivemap and uefi

From: Francisco Franchetti
Subject: Re: drivemap and uefi
Date: Fri, 9 May 2014 19:27:40 -0500

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?

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?

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