I installed ubuntu together with windows 10 in a PC originally running windows 10. In the UEFI firmware I disabled the secure booting and the fast booting and put in the order of booting, ubuntu first.
The grub booting of ubuntu shows the choice to boot with ubuntu or with the windows boot manager. So far, the dual booting seems to work well.
But if I boot Windows from the window booting manager in the menu of booting, when restarting the PC again the booting don't go to that menu and automatically open windows. Checking the UEFI firmware the secure booting and fast booting are kept disabled, but the order of booting move windows back to the first position. (?).
Notice that the windows manager don't remove the grub booting manager, as if I change the order of booting in the firmware, putting again ubuntu first is the grub manager that takes control and I am able to open ubuntu again. What the booting from the windows manager do is to change the order of booting in the firmware, placing windows first, and not removing grub.
bcdedit
in Windows) is good. That tool often overcomes this specific problem. – Rod Smith Feb 26 '16 at 14:11