Ubuntu – Add Windows 10 to GRUB OS list


I recently got a computer from school. It came with Windows 8.1 installed. I then installed another copy of Windows 8.1 (so it would use the built-in Windows Pro license) and upgraded it to Windows 10. I then installed Ubuntu alongside both Windows 8 and 10.

Note that I made a separate 255MB ext2 partition for /boot.

Now, when I boot the computer, I first see a GRUB prompt (I already un-hid the grub prompt 'cuz I like it that way) with Windows 8 and Ubuntu options. However, there is no Windows 10 option. If I select Ubuntu, the computer boots into Ubuntu. However, if I select the Windows 8 option, I then get sent to the Windows bootloader, where it then gives me options to boot either Windows 8 or Windows 10. (However, by this point, the computer has already loaded the kernel and all. Apparently Microsoft misunderstood the concept of a bootloader and decided that that meant "boot practically the entire system before actually showing the bootloader". Typical Microsoft.)

How can I disable the Windows bootloader and add a Windows 10 option to GRUB?

EDIT: Someone has answered telling me to disable the Windows bootloader. However, I still do not know how to add Windows to the GRUB OS list. Can anyone help with this?

EDIT 2: After removing Windows 10 from the Windows bootloader with EasyBCD, it seemed that, after a few reboots, it would continually unhide itself and Windows 10 would reappear. However, I then later deleted Windows 10 from the list of OSes in msconfig, and it seems to have stayed deleted.

However, I STILL have not managed to get Windows 10 to appear in GRUB. It's as if GRUB simply doesn't detect it.

Also, I'll put this in the question so that people see it – I have tried using boot-repair, however, it has NOT helped any.

Best Answer

Sometimes os-prober is wrong.

Look at the UUID of your Windows 10 partition, for exemple:

sudo blkid /dev/sda2

Then edit /etc/grub.d/40_custom, and at the end of the file add:

menuentry "Windows 10" --class windows --class os {
   insmod ntfs
   search --no-floppy --set=root --fs-uuid $your_uuid_here$
   ntldr /bootmgr

Don't forget to change the UUID.

And finally update your grub config file:

sudo update-grub


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