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I have a 1TB HDD with only Ubuntu 16.04 installed on it. But I decided I also wanted Windows 10, so I bought a Samsung 950 PRO 512GB M.2 SSD and installed a copy of Windows 10 Home on it.
I disconnected the cables connecting my harddrive and motherboard, and disabled Launch CSM in BIOS, before installing Windows on my SSD. Windows is now installed and works great on my new SSD. I'm using Windows 10 right now.
I reconnected my harddrive (Ubuntu). I don't know what Launch CSM does, so I didn't enable it. I disabled it because I was following a tutorial. But when I restart my PC, I cannot boot into my HDD. I checked disk management in Windows 10 and my HDD is shown. But in BIOS it is not shown, Windows Boot Manager is the only boot option.
How do I boot into Ubuntu, which is on a separate HDD?