I installed Linux (ParrotOS) on an external hard drive by using a separate bootable flash drive and I think the bootloader (grub) also got installed to that new drive. I can boot both Linux and Windows just fine, but as soon as I disconnect the external hard drive, I just get a grub error instead of being able to boot into Windows.

How can I fix this? I would like to be able to boot to either one when the drive is connected, however just boot to Windows when the drive is disconnected

1 Answer 1


Grub takes away the windows bootloader and adds itself into the boot partition. The hook looks for your external disk in order to start grub - and that won't work.

Grub should be installed on your main disk containing an entry of your external linux partition. In this case Grub would find the windows partition but not the linux if your external disk is not connected..

  • ok but how do I do that? I don't really know what half of that means :) Apr 14, 2022 at 10:27
  • well, obviously you've installed grub - but on the wrong disk. Make it right. Since you did not provide any information how exactly you installed it, which distro you are using, don't expect a precise answer. Instead read on how to install grub (for the linux distro you are using)
    – kanehekili
    Apr 14, 2022 at 10:32
  • cool. edited my answer to include some of that info. the distro is ParrotOS and I installed it using a separate bootable flash drive. Is it possible to install grub on the windows partition? Apr 14, 2022 at 13:16
  • @DanMoldovan If your system uses UEFI-style boot, GRUB could fit nicely alongside the Windows boot manager on the ESP partition. If your system uses BIOS-style boot, it's a bit trickier but doable. On a BIOS-boot system, it might be better to add a Linux boot option to the Windows bootloader, e.g. using the EasyBCD utility. That would make the required changes in the Windows side in such a way that Windows should not "self-heal" them away in any situation - and even if a future Windows update changes that, EasyBCD should allow re-making the changes in a simple way.
    – telcoM
    Apr 14, 2022 at 19:11

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