How to fix the broken grub of a dual boot machine after Windows 10 update

In certain cases, the Windows 10 feature upgrade is breaking the grub in a dual boot PC. This would lead to grub rescue mode and prevents both Linux and Windows from booting. Follow the below steps to update the grub and enable both the operating systems.

Grub Rescue

If the grub is corrupted because of the windows update, the potential error message that you may get is “error: unknown filesystem” followed by cursor blinking at “grub rescue“.

Steps To Fix The Grub

Follow the below steps to locate the grub file in the available partition and temporarily boot into the Linux environment.
1. Execute the “ls” command, which lists all the disk partition
2. Execute the command ls /boot/grub
3. This would return the type of the filesystem if it is the partition that contains the bootloader. Else, this would return a message as “unknown filesystem”
4. Set the root and prefix with the identified file system
5. Load the module to the kernel by executing the command “insmod normal”
6. Execute the command “normal” and this reboot the machine to Linux

Update Grub

Once you are inside the Linux Operating System, the next step is to update the grub by executing the command “sudo update-grub” in the terminal to make the changes permanent in a Ubuntu-based Linux Machine.

With that, the grub would be back to normal and now you can view the entries for both Linux and Windows at the boot.