How to fix update-grub: error: cannot find a GRUB drive for /dev/sdX in APT

The device.map file may be missing or outdated. Regenerate it by running:

sudo grub-mkdevicemap
sudo update-grub

This recreates the device.map file based on current hardware and should resolve the mapping issue in most cases.

If you are updating GRUB from a live USB or recovery environment, ensure you have properly mounted the root filesystem and any required partitions:

mount /dev/sdXY /mnt
mount /dev/sdXZ /mnt/boot
sudo chroot /mnt

Before chrooting, also bind critical filesystems:

mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /proc /mnt/proc
mount --bind /run /mnt/run
mount --bind /sys /mnt/sys

Then run update-grub from within the chroot environment.

If your system uses UEFI firmware, ensure the EFI System Partition (ESP) is properly mounted:

mount /dev/nvme0n1p3 /mnt
mount /dev/nvme0n1p1 /mnt/boot/efi
arch-chroot /mnt
grub-mkconfig -o /boot/grub/grub.cfg
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=grub

Replace the device names with your actual partitions. Ensure the EFI partition has at least 100 MB of space.

Check if the partition is marked as bootable in the partition table:

sudo fdisk -l /dev/sdX

Look for a "*" in the Boot column. If the boot flag is missing, set it with:

sudo fdisk /dev/sdX

Then type "a" to toggle the boot flag on the correct partition, then "w" to write changes.

If GRUB cannot extract UUID information from your filesystem, it falls back to device names like /dev/sdXX. Verify your filesystem is supported:

df -T

Common supported filesystems include ext4, btrfs, and xfs. If using an unsupported filesystem, you may need to manually edit /boot/grub/grub.cfg and replace device names with UUID values:

blkid /dev/sdXY

Use the UUID output to update your GRUB configuration if needed.

If grub-probe continues to fail even after proper mounting, you can replace the grub-probe binary with a shell script that outputs a known filesystem type:

sudo mv /usr/sbin/grub-probe /usr/sbin/grub-probe.orig
sudo tee /usr/sbin/grub-probe > /dev/null << EOF
#!/bin/bash
echo ext4
EOF
sudo chmod +x /usr/sbin/grub-probe

Run update-grub, then restore the original binary:

sudo mv /usr/sbin/grub-probe.orig /usr/sbin/grub-probe

Use this only if all other solutions fail, as it bypasses GRUB filesystem detection.