Elemental on Raspberry Pi Fails OEM/Persistence Reset due to Empty /oem Directory

[atoy3731]

elemental-toolkit version:
elemental-operator-1.5.3 (via Rancher UI Extension)

CPU architecture, OS, and Version:
Raspberry Pi 4B - 8GB

Describe the bug
When "repurposing" an Elemental Raspberry Pi node, the reset process fails and is unable to re-register to Rancher to be utilized again. The elemental-register-reset.service service on the Pi has 2 main errors:

Initially:

failed installing grub: open /sys/firmware/efi/efivars/Boot0000-8be4df61-93ca-11d2-aa0d-00c098032bc: read-only file system

Followed repeated by:

initializing configuration: merging config: open /oem/registration/config.yaml: no such file or directory

To Reproduce

1. In Rancher, create a new Registry Endpoint using this configuration (potentially modifying your device):

   config:
     cloud-config:
       users:
         - name: root
           passwd: root
     elemental:
       install:
         debug: true
         device: /dev/mmcblk0
         disable-boot-entry: true
         poweroff: false
         reboot: true
         snapshotter:
           type: loopdevice
       registration:
         auth: tpm
         emulate-tpm: true
         emulated-tpm-seed: -1
       reset:
         enabled: true
         reboot: true
         reset-oem: true
         reset-persistent: true
   machineInventoryLabels:
     type: raspberry-pi

2. On a Raspberry Pi device, ensure you have terminal access (via a monitor and keyboard) and follow the Elemental documentation to produce a raw image, specifically the Preparing the seed image (aarch64) manually section.

3. Once the raw image is produced, burn it to a USB flash drive and plug it into a Raspberry Pi 4B with an empty SD card. After boot and install, the Raspberry Pi should show up as an active Machine in Rancher's Elemental UI.

4. Create an Elemental Kubernetes cluster with a single node that matches the Machine's labels (type=raspberry-pi)

5. Once the cluster is healthy, delete the cluster.

6. Wait for the Raspberry Pi to restart via the monitor, when it restarts, check the logs via journalctl -u elemental-register-reset.service

Expected behavior
Raspberry Pi Elemental node rejoins and becomes active in Rancher after OEM/Persistence reset.

Logs

Additional context
N/A

[davidcassany]

I have been looking at it and I think this was already fixed in head but not backported. Gonna try to validate backporting it to v2.1.x series fixes the issue.