Chris Murphy wrote:
What you should revert back to UEFI only, with Secure Boot enabled, and reinstall CentOS, deleting the previous partition/mount points including the BIOS Boot partition that was created for CentOS's bootloader.
The gotcha is that with Secure Boot enabled, the CentOS GRUB-efi package doesn't support chainloading the Windows bootloader. This is getting fixed in Fedora 24 but I have no idea how long it'll take to get to CentOS 7. You could either disable Secure Boot (which I don't recommend) or you switch between CentOS and Windows using the firmware's boot manager. You'll have to figure out which F key brings up the boot manager. On my Intel NUC it's F10, *shrug*.
May I ask a couple of questions which I'm afraid betray my ignorance.
1. Why is it advisable to "revert back to UEFI"? Is this just a safety measure? I would have thought that if an intruder had got in this far, enabling him to install unsigned modules, he would have you at his mercy anyway?
2. I installed CentOS-7.2.1511 from a Live USB stick, and I have a Windows 10 partition that I can boot into. So I assume that UEFI is not used by default? Will it become so at some point?