Ubuntu in dual-boot doesn't start after reinstalling Windows 10 [duplicate]
From Windows disable Fast Boot:
- Search for and open “Power options” in the Start Menu.
- Click “Choose what the power buttons do” on the left side of the window.
- Click “Change settings that are currently unavailable.”
- Under “Shutdown settings” uncheck “Turn on fast startup”.
Then boot from a live Ubuntu CD (or USB) then install Boot repair tool
sudo apt-add-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair
Run boot repair by typing boot-repair command then click on Recommended repair button.
Good luck.