Dual Booting NixOS and Windows

From NixOS Wiki
Revision as of 18:37, 29 May 2018 by imported>Samueldr (→‎EFI + Grub: Fixes comment, the previous statement wasn't false, but may have been surprising when compared to the installation section of the manual)

MBR

All MBR bootloaders will need at least some configuration to chainload Windows.

MBR + Grub

When using MBR on your disk then you can configure grub chain-loading:

{
  boot.loader.grub.enable = true;
  boot.loader.grub.version = 2;
  boot.loader.grub.device = "/dev/sda";
  boot.loader.grub.extraEntries = ''
    menuentry "Windows 7" {
      chainloader (hd0,1)+1
    }
  '';
}

Source: https://www.reddit.com/r/NixOS/comments/31lx3i/windows_and_nixos_dual_boot/

EFI

After setting up a 256mb EFI Partition dualboot should work out of the box (at least for windows10)

Source: https://zimbatm.com/journal/2016/09/09/nixos-window-dual-boot/

EFI + Grub

systemd-boot can not load EFI binaries from other partitions, and a pre-exisitng EFI partition from a Windows install may be smaller than we would like our /boot partition to be. If we still want Windows and NixOS to use the same EFI partition, we can use GRUB instead.

Here we assume:

  • the EFI partition has been mounted on /boot/efi
  • $FS_UUID is the UUID of the EFI partition
  • the boot.loader.systemd-boot.enable = true; line added to configuration.nix by nixos-generate-config has been removed
{ config, ... }:

{
  boot.loader = {
    efi = {
      canTouchEfiVariables = true;
      # assuming /boot is the mount point of the  EFI partition in NixOS (as the installation section recommends).
      efiSysMountPoint = "/boot";
    };
    grub = {
      # despite what the configuration.nix manpage seems to indicate,
      # as of release 17.09, setting device to "nodev" will still call
      # `grub-install` if efiSupport is true
      # (the devices list is not used by the EFI grub install,
      # but must be set to some value in order to pass an assert in grub.nix)
      devices = [ "nodev" ];
      efiSupport = true;
      enable = true;
      # set $FS_UUID to the UUID of the EFI partition
      extraEntries = ''
        menuentry "Windows" {
          insmod part_gpt
          insmod fat
          insmod search_fs_uuid
          insmod chain
          search --fs--uid --set=root $FS_UUID
          chainloader /EFI/Microsoft/Boot/bootmgfw.efi
        }
      '';
      version = 2;
    };
  };
}

Sources: