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Suppose, I have a machine with UEFI and GPT-partitioned hard drive. I have an Ubuntu system installed on it and GRUB2 in UEFI system partition.

Then I install Windows 10 and its boot loader to UEFI system partition as well. Will GRUB2 see the new Windows boot loader and allow me to chainload it? (Probably not?)

So, I'll probably have to update GRUB2 after installing Windows, if I want to chainload Windows from GRUB menu?

  • First you need to recover Ubuntu after installing windows – GAD3R Sep 20 '16 at 19:56
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You will need to boot into Ubuntu as Windows 10 will have over written the first stage of the GRUB boot loader from the maste boot record (MBR). You can use a Ubuntu CD in rescue mode to do this.

Then you will need to reinstall GRUB to the MBR which is an option in the Ubuntu rescue disk.

Alternatively if you have some other way to boot into Ubuntu you can use this command to update grub

sudo update-grub
  • Tom, as I've stated in the question I'm using GPT, not MBR. So, GRUB stages 1 and 1.5 are not in MBR + first 32KB of disk (MBR gap) anymore. Whole GRUB is in EFI System Partition (ESP) as well as Windows bootloader. EFI firmware will load GRUB from ESP and usually GRUB detects other bootloaders in ESP and allows to chainload them in GRUB menu. I want it to detect Windows Bootloader, but not sure, whether this requires GRUB update or not. Your answer is relevant to MBR, but not to GPT case (thanks for taking the time to write it, though). – Boris Burkov Sep 21 '16 at 11:02
  • Ah yes missed that you had installed to EFI, sorry – Tim Fletcher Sep 21 '16 at 18:03
  • You will need to change the order using efibootmgr but I've not had to do much with efibootmgr for a while so not going to try and help and risk breaking your system :) – Tim Fletcher Sep 21 '16 at 20:30
  • Oh, I called you "Tom", not Tim in comment. I'm very sorry. Thanks for you help. – Boris Burkov Sep 22 '16 at 8:58
  • No worries Bill :p – Tim Fletcher Sep 22 '16 at 9:04

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