Adding UEFI Windows 10 Menu Entry to Grub

If you install Ubuntu first and Windows later, you’ll notice that it’s not possible to boot into Linux anymore. As Windows boot loader doesn’t really handle Linux, you’ll need to tell Winodws to use Grub.

Once you’re in command prompt with administrative privileges, you can execute:

> bcdedit /set {bootmgr} path \EFI\Ubuntu\grubx64.efi

After reboot Grub will show it’s ugly face and you’ll have another problem – there are no Windows entries.

To get them into Grub menu, one can simply update grub:

$ sudo update-grub

On most Linux distributions this will trigger OS Prober and Windows Boot Manager entry will magically appear. However, if you have OS Prober disabled or you want to disable it in future for some reason, you can add manual entry too:

$ cat << EOF | sudo tee /etc/grub.d/25_windows
#!/bin/sh
exec tail -n +3 \$0
menuentry 'Windows 10' {
  savedefault
  search --no-floppy --set=root --file /EFI/Microsoft/Boot/bootmgfw.efi
  chainloader (\${root})/EFI/Microsoft/Boot/bootmgfw.efi
}
EOF

$ sudo chmod +x /etc/grub.d/25_windows

$ sudo update-grub

In either case, boot menu should now offer you option to get into Windows.

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