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I installed Ubuntu on an existing Windows 10, dual boot was fine for some months. Now I try again and it doesn't work anymore. grub-update doesn't find any OS besides Ubuntu. Using boot-repair from a USB-Stick finds the EFI partition on nvmen1p1, but booting from that results in

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

nvmen1p2, where the real Windows 10 is located, is not found, even from the USB stick.

sudo os-probe on regular Ubuntu finds nothing.

Here is the pastebin: https://paste.ubuntu.com/p/H54w8bCwws/

Any advice?

G. S.
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  • You have mixed BIOS & UEFI. Your Windows is in the old BIOS/MBR configuration. Microsoft has required vendors to install Windows in UEFI boot mode with gpt partitioning since 2012. So most hardware now is UEFI. But then you orginally installed Ubuntu in UEFI boot mode. It looks like you have reinstalled grub in BIOS boot mode, but have boot flag on 3 partitions. It should only have boot flag on sda1, the Windows boot partition. Grub does not use boot flag. Also grub only boots working WIndows. You may have to temporarily reinstall Windows boot loader, fix Windows or turn off fast start up. – oldfred Mar 29 '22 at 13:44
  • Thanks. I changed the boot flags. How do I reinstall the Windows boot loader or fix Windows? I believe fast startup is already off. – G. S. Mar 29 '22 at 14:19
  • Is it possible to convert Windows to GPT/UEFI without loosing it? – G. S. Mar 29 '22 at 14:25
  • I have seen several sites/posts where users try converting. But almost all have come back and posted they had to do a new clean install. So have good backups. The partitioning with WIndows is totally different between UEFI/gpt & BIOS/MBR. https://msdn.microsoft.com/en-us/library/windows/hardware/dn898510%28v=vs.85%29.aspx#RecommendedPartitionConfigurations & https://msdn.microsoft.com/en-us/library/windows/hardware/dn898504%28v=vs.85%29.aspx – oldfred Mar 30 '22 at 13:07
  • Does this answer your question? Unable to boot into Windows after installing Ubuntu, how to fix? – karel Mar 31 '22 at 09:15

2 Answers2

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Add it manualy in your grub.cfg. Add

menuentry "Windows 10" --class windows --class os $menuentry_id_option 'osprober-efi-F024-2799' {
insmod part_gpt
insmod fat
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root F024-2799
else
search --no-floppy --fs-uuid --set=root F024-2799
fi
chainloader /EFI/Microsoft/Boot/bootmgfw.efi }


below the line ### BEGIN /etc/grub.d/30_os-prober_proxy ###. It can be another number than 30, but 30 is the most common number for os-prober.

Remember that after an sudo update-grub you will have to do this again. And also make backup first.

If it works please accept the answer. If it doesn't, report back and we will look for other options.

HomerSimpson
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  • That fails with: 
    error: no such device: F024-2799.
error: file `/DEFI?Microsoft/Boot/bootmgfw.efi' not found.
    – G. S. Mar 29 '22 at 14:00
  • Take a look at:

    http://answers.microsoft.com/en-us/windows/wiki/windows_10-performance/troubleshooting-windows-8-and-10-failure-to-start/bcf8503c-1b39-4827-9734-a64fef725d0f

     – HomerSimpson Mar 29 '22 at 14:55
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I got it working again. Rough steps:

  1. Add small GUID partition at the beginning of the disk.
  2. Download Windows 10 and install on external hard disk.
  3. Run from there and repair (had to go down to the command line and follow some advice I found elsewhere, can't remember).
  4. Now I can switch between Windows and Ubuntu in
G. S.
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