I asked this on Stack Overflow but apparently it's more suited for here, I hope someone is able to help. This issue is a little broad and requires some background.
I have had Windows 7 installed on one SSD and Linux Ubuntu installed on a partition of a separate HDD for a fair amount of time now. I would choose which to boot into from BIOS and there was no issue. I recently got a smaller but faster SSD and my goal was to install Windows 10 and a newer version of Ubuntu on separate partitions of said SSD, and reuse the old SSD and HDD for a fair amount of fast and slow storage. I've done just that and they work great once booted but I have some problems with booting.
I started with installing Ubuntu. Once I did I no longer had the boot option in BIOS for some reason, but it wasn't a problem because my PC would automatically boot into GRUB and from there I could select Ubuntu. After this I got Windows 10 on the remaining partition. Now my PC automatically boots into Windows 10, and BIOS still has no option to boot into just the Ubuntu partition or the Windows 10 partition.
I don't have a very thorough understanding of the difference between BIOS and GRUB, how they work, whether GRUB is software on the drive where Ubuntu is or is firmware. However I am pretty sure that to fix this I would need to make a boot manager of some kind, that my PC will automatically boot to when turned on, that can let me select which partition to boot into. To do this however, I have no clue where to start. Can I get a helping hand at finding a starting point here?
