So I have four partitions on my SSD (/dev/sdb):

  • sdb1: A Windows 8.1 x64 installation
  • sdb2: Arch boot
  • sdb3: Arch swap
  • sdb4: Arch root

One of my media drives is /dev/sda.

I've installed grub onto sdb, but grub won't show my Windows installation (no number of grub-mkconfigs has helped me so far) and it doesn't show up with os-prober either.

However, if I leave my Windows install USB plugged in and leave my computer alone, it asks to boot from USB (which I ignore) and proceeds onto Windows (skipping grub).

My BIOS boot order is CD > USB > HDD.

Drive uses MBR and neither Windows or Arch are using UEFI.

How I can get grub to recognise Windows is there? Because Windows is clearly working fine. Also why does Windows bootloader start instead of grub even if I'm not booting from the USB?


Turns out that by mounting the Windows partition (I mounted it to /mnt/windows), os-prober detected /dev/sda1 as having a Windows bootloader on it for some reason. Not sure why, but I'll take what I can get.

Perhaps I'll look into it at some stage, but for now I'll just let my current copy of Windows piggyback off of it.

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