Dual-boot Ubuntu 12.10 on UEFI along Windows 8

Question

Hello after a successfull installation of Ubuntu 12.10 amd64, I am now unable to boot Windows 8.

Here are my actions:

1. Made room (15 GB) for Ubuntu from Windows 8 Computer Managment
2. Boot Ubuntu 12.10 amd64 LiveUSB with EFI and with Secure Boot enabled
3. Created 2 new partitions at the end (13 GB Ext4 Root amd 2 GB Swap)
4. Selected Windows 8 EFI System Partition to install bootloader

Grub gives me at boot:

1. Ubuntu (works without problems)
2. Windows Recovery Environment (lots of errors)
3. Windows 8 (2 error messages describe just below)

The 2 error messages are:

• error: can't find command drivemap.
• error: invalid EFI file path

Answer 1

Found a temporary solution.

Append to /etc/grub.d/40_custom

menuentry "Windows 8" {
   set root='(hd0,gpt1)'`
   chainloader /EFI/microsoft/BOOT/bootmgfw.efi
}

Warning: gpt1 here is my ESP, yours could be different, like gpt3

Now apply changes to grub

update-grub

Warning: If you boot Windows 8, grub will be replaced by Windows Boot Manager as default boot manager. I haven't found a solution until now.

Answer 2

The wrong Windows entries in GRUB are due to this bug: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1024383

Solution: run Boot-Repair's Recommended Repair from a liveCD (or liveUSB).

Answer 3

I found a way to shut Windows 8 up. See http://superuser.com/questions/499923/preinstalled-windows-8-and-linux-uefi-dual-boot-on-a-laptop/528581

Under W8, in an elevated privilege command window, run powercfg /h off. By the time you do this, W8 may already have overwritten the EFI partition. It took me a few iterations of changing bootmgfw.efi and having it reset until it stuck, but now I'm happy.

I can't tell if just booting W8 is enough, or if you have to log in and then reboot. Perhaps somebody with more patience (I was working on this for more than half a day) can tell.