Laboratorium Komputerowe Progmar

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Restoring broken Grub bootloader

If we stucked to broken Grub bootloader after windows update on the computer with multi-operating systems and we end-up with following message:

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

then first we should type in ls command to list available partitions:

grub rescue> ls

Next we search for Linux partition by issuing commands of following syntax:

grub rescue> ls (hd0,gpt1)

if we get:

(hd0,gpt1): "Filesystem is unknown"

then we check other partitions until we get message below:

(hd0,gpt6): "Filesystem is ext2"

Now we know that this is a Linux partition so we should issue following commands:

grub rescue> set boot=(hd0,gpt6)
grub rescue> set prefix=(hd0,gpt6)/boot/grub
grub rescue> insmod normal
grub rescue> normal

And this is it. We end up with working Grub menu, that give us possibility of choosing operating system we want to load.

If we load Linux we should permanently repair Grub menu by following instructions in article: useful Grub commands