error unknown filesystem entering rescue mode grub rescue ubuntu

In this POST I will show how to get rid of

error: unknown filesystem.
Entering rescue mode...
grub rescue

Switch on the System, wait untill you get the Grub Rescue Screen.
Type the following commands

ls

It will display list of partions you had in your system.
You will get something like this (hd0),(hd0,msdos1)(hd0,msdos2)(hd0,msdos3) based on no of partitions

set prefix= (hd0,msdos1)/boot/grub

If it’s not the root drive you will get an error message "unknown filesystem". In that case try the same command with the next partion.
You need to find which drive is Ubuntu root. For that type the following:
Ex: set prefix=(hd0,msdos2)/boot/grub

set prefix=(hd0,msdos1)/boot/grub

insmod normal

normal

sudo update-grub

sudo grub-install /dev/sda

If you are not getting an error: You can proceed to the next command after that:
Your PC will now boot successfully. Now select Ubuntu & login.
Open Terminal( Ctr+Alt+T or use the search)
Now the bootloader error is fixed you should be able to boot your System normally & even your data is intact.