Manjaro XFCE (BTRFS + grub-btrfs) broken after update – grub_memcpy error → emergency shell (cannot mount root UUID)

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1

Hi,

After a recent system update on Manjaro XFCE, my system stopped booting.

First error I encountered:

error: symbol 'grub_memcpy' not found
Entering rescue mode...

After attempting repair (update-grub, etc.), now I get:

ERROR: Failed to mount 'UUID=17b5f31d-bcb0-49e2-96cd-a71cf65990a5' on real root
You are now being dropped into an emergency shell.

System configuration:

  • Manjaro XFCE (rolling release)
  • UEFI system
  • BTRFS root filesystem
  • Subvolumes:
    @, @home, @cache, @log
  • Timeshift with BTRFS snapshots enabled
  • grub-btrfs installed

fstab (relevant part):

UUID=… / btrfs subvol=@,defaults,compress=zstd:1 0 0

Disk layout:

  • /dev/sda7 → BTRFS (root)
  • EFI partition mounted at /boot/efi

What I already checked:

  • UUID of /dev/sda7 matches fstab
  • Subvolume @ exists
  • Filesystem mounts manually from live USB
  • No obvious BTRFS corruption

This started right after a system update, so I suspect:

  • broken GRUB update
  • initramfs issue
  • or incompatibility with grub-btrfs

Has anyone experienced something similar recently?
Any ideas what to check next or how to properly repair GRUB/initramfs in this setup?

Thanks in advance.

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2

Welcome to the forum! :vulcan_salute:

Considering that your root filesystem is on /dev/sda7, I suspect that you’re running a multi-boot system, and that your /boot/efi/EFI/boot/bootx64.efi and /boot/efi/EFI/manjaro/grubx64.efi are out of sync.

I would recommend chrooting into your installed system from a USB stick with a recent Manjaro ISO, and then installing and running install-grub. It’s a shell script that will synchronize your UEFI stubs.

If the manjaro-chroot script on the live USB does not work — it should now, but if your ISO is not a recent one, then it’ll have difficulty with btrfs — then please use the method as laid out in the HowTo below. :backhand_index_pointing_down:

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