Installing NixOS made Windows disappear from boot menu

Help
1

Hello, I have a pc with two separate drives : An NVME SSD for Windows and a SATA SSD that I use for Linux.

Recently I decided to mess around with NixOS again so I had a fresh installation on the SATA SSD, did some basic configuration and then had to use Windows because anticheat

But I could only see two options :

  1. NixOS
  2. Linux Boot Manager

I haven’t made any significant changes like changing the boot loader, just basic stuff like installing some programs.

I looked around online including some posts from this forum and tried listing the EFI boot options using a command (There was only the ones I mentioned, no Windows) so right now I am kind of at a loss.

Thank you for your help!

3

It’s likely that your fresh installation messed up with your efi bootloader. Or created another one.

I don’t know the magic incantation to unblock you, but I have been similar situations many times and it left a bad taste in my mouth. Here are all the options I’ve had to use with varying level of anger:

  • use the motherboard boot menu and select the disk where Windows is, every time
  • change your boot order / unplug the linux drive
  • use efibootmgr to fixup the bootloader

Try at least the first one, if it doesn’t boot then you have bigger issues.

Hopefully someone more knowledgeable will help you and I’ll try to follow along as I currently have a machine in the same state (though slightly different setup). What did not work for me, but you can try, is to add a manual entry in your configuration.nix or force os-prober. I don’t think your issue is specific to NixOS but have a look at Dual Booting NixOS and Windows - Official NixOS Wiki anyway.

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