Fix Ubuntu Grub Boot Error

This error happens usually when the /boot folder is full and grub doesn’t update/install properly when the system is updated.

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error: symbol 'grub_file_filters' not found. 

Entering rescue mode... 

grub rescue>

One way to fix this is to boot with a Live USB image, mount the boot drive, and update/install grub again.

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mount /dev/<vg/root> /mnt

mount -t proc none /mnt/proc

mount -o bind /dev /mnt/dev

mount -t sysfs /sys /mnt/sys

chroot /mnt

grub-install /dev/sda

update-grub