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The relevant windows drive install is:

Disk /dev/sde: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xe55015e8

Device     Boot     Start       End   Sectors   Size Id Type
/dev/sde1            2048 975849471 975847424 465.3G  7 HPFS/NTFS/exFAT
/dev/sde2       975849472 976771071    921600   450M 27 Hidden NTFS WinRE

How can I get grub2 to actually load Windows 10?

Following this answer, I tried: 

menuentry 'Windows 10' {
  insmod part_gpt
  insmod search_fs_uuid
  insmod ntfs
  insmod chain
  search --fs-uuid --set=root --hint-bios=hd4,msdos1 --hint-efi=hd4,msdos1 --hint-baremetal=ahci4,msdos1 343419363418FC94
  chainloader (${root})/Windows/Boot/EFI/bootmgfw.efi
  boot

I kept getting ntfs.mod not found errors for all the insmod commands so tried to remove them. Still, nothing.

My /etc/grub.d/40_custom read:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry 'Microsoft Windows 10' {
  set root='(hd4,1)'
  chainloader +1

This fails with no boot detected.

  # same header as above.
  search --no-floppy --fs-uuid --set=root '343419363418FC94'
  chainloader /bootmgr
  boot

This fails with unknown file system & no boot detected.

  # same header as above.
  insmod part_gpt
  insmod search_fs_uuid
  insmod ntfs
  insmod chain    
  search --fs-uuid --set=root --hint-bios=hd4,msdos1 --hint-efi=hd4,msdos1 --hint-baremetal=ahci4,msdos1 343419363418FC94
  chainloader (${root})/Windows/Boot/EFI/bootmgfw.efi
  boot

This fails with ntfs.mod not found, followed by unknown file system.

  search --fs-uuid --set=root --hint-bios=hd4,msdos2 --hint-efi=hd4,msdos2 --hint-baremetal=ahci4,msdos2 6ACAB410CAB3D693
  chainloader (${root})/Recovery/WindowsRE/boot.sdi
  boot

This fails with path not found, despite it being the right path as checked by mounting the drive.

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7
  • Booting from fedora, what's the folder tree found under /boot/efi/? Are you able to see something like /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi? Or can you see ./EFI/Windows/Boot/EFI/bootmgfw.efi if you mount hd4 somewhere? Commented Mar 16, 2016 at 17:36
  • @Roflo: No, nothing like that at all. Windows is installed on another disk. Mixing boot loaders has lead to so much trouble that I do not bother any more. All I want is to let grub2 decide it should pass the torch to something else which worked fine in non-EFI mode. Commented Mar 17, 2016 at 8:27
  • Ok. What I wanted to ask is: Have you checked that your path to bootmgfw.efi is correct within hd4? Commented Mar 17, 2016 at 15:24
  • FWIW, last time I has to struggle with this (win8) all I had to do is set root=(hd0,2) and chainloader /EFI/Microsoft/Boot/bootmgfw.efi (exact options will differ for your case, of course). Commented Mar 17, 2016 at 15:26
  • @Roflo: Yes, by mounting the drive in linux and checking. However, grub2 seems to think this is an unsupport file system when I do pass it the path. It cannot load ntfs.mod from anywhere. Commented Mar 17, 2016 at 15:29

1 Answer 1

Reset to default
1

Sadly, the only way to solve this was to re-install Windows 10 in UEFI mode, then re-install Fedora in UEFI mode. Then, some messing about with the order of loading. Finally, I have both systems working.

What a mess... :(

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