Unknown file system - Solved grub rescue error | Không khởi động được máy tính

This error can happen when you're using dual os and edit your disk in windows or when windows install some updates. However, it's very easy to fix.
First, type "ls" to check every partition you have. Then check the partition one by one as shown above. if it return is "unknown file system", keep checking.
If it return is "bad filename" or "filesystem is ext2" or some informations of linux os as img.old, vmlinuz.old files. Type: 

set boot=(your disk, your partition)

set prefix=(your disk, your partition)/boot/grub/

insmod normal

normal

Then, go to your linux os and open terminal, install and update your grub:

sudo grub-install /dev/sda

sudo update-grub

Explore more: Fix lost Grub2 after install dual boot linux and windows