In my duel boot system (Ubuntu & Windows 10), during the Ubuntu upgrade process, i lost the grub boot menu options. It directly boots to Ubuntu and these is no option to select my Windows OS during boot. After a lot of research and help i found a solution in my case.
Fix Grub Boot Menu Not Showing & No Windows Boot Option in Dual Boot
Open the terminal application (ctrl+alt+t) in your Ubuntu (or any other Linux system) and run below command.
sudo nano /etc/default/grub
Run your Ubuntu password if needed.
It will open the grub file in the nano command-line editor.
Now using the arrow keys location the below line.
GRUB_TIMEOUT_STYLE="hidden"
And change this to
GRUB_TIMEOUT_STYLE="menu"
And also add below line . (Or find below line and uncomment it)
GRUB_DISABLE_OS_PROBER="false"
Save the file. To save the file press Ctrl + X on your keyboard. This will attempt to exit nano. Now enter Y and hit the enter key. Now you will be asked to give a name to the file. Simply hit the Enter key on your keyboard.
How to Save File Using Nano Editor
Now in the terminal app run below command.
sudo update-grub
Now restart your system. Now you will get Grub Boot menu options.
