Involuntary BIOS dual boot

[Gabethebabe]

Hi all, I have a Toshiba Satellite C-50 laptop that was, until recently, sporting a standard WIN10 / Linux Mint 64-bit dual boot.
Until I choose to upgrade from 18.2 to 18.3 through the update manager. That broke my GRUB2, as now I booted directly into WIN10.

So I burned the Linux Mint 18.3 64-bit boot disk and tried to repair GRUB2.

Problem number 1: My stupid laptop doesn't boot from CD or USB unless it is in CSM mode. I have tried everything, booting through WIN10 recovery mode to USB/DVD, mashing the F2 button and changing boot order, mashing F12 button to get into Toshiba boot menu and picking USB or DVD. To no avail, it boots from HD into Windows 10 every time. EVERY TIME.

So in BIOS I picked CSM, booted into the recovery disk and tried to repair GRUB2. I could not do it. Error message every time. Used chroot method. Failed. Downloaded and ran the boot repair utility and it failed, it told me it would only work in EFI mode.

So running out of options, I decided to just reinstall Linux Mint. After doing that I now have the funny situation that if I choose UEFI boot in BIOS, I boot into Windows and if I use CSM boot, I boot into Linux Mint.

How can I get GRUB2 to work again?

[Gabethebabe]

bump

Too tough, dis one?

[fabien85]

Boot windows, get refind and install it using the windows instructions.

Dont forget to disable secure boot before all this, if you have not done it already.