Last time I tried to dual boot windows and ubuntu I lost Grub, and after a couple mistakes had to reinstall. I still want windows, but I don't want to get burned again. I've been doing some research and saw that I probably would want to disable fast boot and mark windows boot manager as inactive. Does this sound right, or should I do something else? my pc isn't powerful enough to run windows in a vm except for very mild workloads. Thanks. NOTE: ubuntu is already installed.

1 Answer 1


It is not recommended to install Windows after installing Ubuntu. It is easier to do the opposite: install Windows then install Ubuntu. Indeed the installation of Windows replaces GRUB by Windows Boot Loader.

You must reinstall GRUB in order to use Ubuntu. A simple way to do this is to use a Live version of Ubuntu. Once Live Ubuntu has been loaded, open a terminal and install the boot repair utility with the following commands:

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair

Then start the utility with the boot-repair command or simply from the application menu and select the Recommended repair.

Boot repair utility screenshot from (https://help.ubuntu.com/community/Boot-Repair)

When repair is finished you should be able to boot on Ubuntu after a reboot. For more information have a look at this article in the Ubuntu Community Wiki. The screenshot comes from this article.

  • Thanks, that worked. However, something else I had to do is run this In the Windows admin command prompt: bcdedit /set {bootmgr} path \EFI\ubuntu\shimx64.efi .Possibly put this in your answer to help future people? also, maybe add to only select the first Windows option or it might reset the bootloader.
    – Eric Ryan
    Mar 22, 2020 at 20:25

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