I have a dual boot with Windows 10 and ubuntu 16.04. Last night i got the option "update and shut down" and i clicked that. Today i started my system, and everything was normal. I started ubuntu, and shut down normally. But since then, whenever i start, nither the bios screen nor grub appears. Everything is just blank for 30 seconds and windows starts up. I have tried a lot of things but to no avail. I suspect this has something to do with the windows update. I had fast startup disabled, and windows 10 was the default option in grub menu.