Recovering my encrypted Manjaro installation after an update

After updating Manjaro, my system stopped booting and GRUB displayed this error:

Error: grub_is_using_legacy_shim_lock_protocol not found

These are the recovery steps that restored my installation.

Historical note: This procedure worked on my machine in October 2025. I no longer use Manjaro and have not revalidated it against current releases. Treat it as a record of one recovery, not a maintained guide, and confirm the current procedure in the Manjaro documentation or support forum before making changes.

My system used a UEFI installation on /dev/sda, with two partitions:

• /dev/sda1 was the EFI system partition.
• /dev/sda2 contained the LUKS-encrypted root filesystem.

The commands below are specific to that layout. Do not copy the device names without checking your own partitions first. Installations using another disk, LVM, Btrfs subvolumes, or a different boot layout require different mount steps.

1. Boot from a Manjaro live USB and open a terminal.

2. Inspect the available filesystems and identify the encrypted root and EFI system partitions:

   lsblk -f
   

3. Open the encrypted root partition. I used a2 as a temporary device-mapper name:

   sudo cryptsetup open /dev/sda2 a2
   

4. Mount the decrypted root filesystem:

   sudo mount /dev/mapper/a2 /mnt
   

5. Create the mount point for the EFI system partition:

   sudo mkdir -p /mnt/boot/efi
   

6. Mount the EFI system partition:

   sudo mount /dev/sda1 /mnt/boot/efi
   

7. Enter the installed system with manjaro-chroot:

   sudo manjaro-chroot /mnt
   

8. Reinstall GRUB using the Manjaro helper available on my installation:

   install-grub
   

9. Exit the chroot, unmount the filesystems, and restart:

   exit
   sudo umount -R /mnt
   sudo shutdown -r now
   

After the restart, my system booted normally again.

Reference#

• Manjaro forum: Get a black screen with "Error: grub_is_using_legacy_shim_lock_protocol not found"