operating-system: Update to build `dev20220227` failed because `RAUC_SLOT_BOOTNAME` is empty

Describe the issue you are experiencing

I’m trying to upgrade my dev20220225 build to dev20220227. It seems the RAUC_SLOT_BOOTNAME is empty, because it failed on the cp command from line 60 of the RAUC hook file.

The same happens when trying to upgrade HASSOS 7.4 to dev20220227.

What operating system image do you use?

ova (for Virtual Machines)

What version of Home Assistant Operating System is installed?

7.4

Did you upgrade the Operating System.

Yes

Steps to reproduce the issue

1. Run HASSOS 7.4 or dev20220225.
2. Upgrade to dev20220227.

Anything in the Supervisor logs that might be useful for us?

22-02-28 16:21:19 INFO (MainThread) [supervisor.os.manager] Fetch OTA update from https://os-builds.home-assistant.io/8.0.dev20220227/haos_ova-8.0.dev20220227.raucb
22-02-28 16:21:25 INFO (MainThread) [supervisor.os.manager] Completed download of OTA update file /data/tmp/hassos-8.0.dev20220227.raucb
22-02-28 16:21:33 ERROR (MainThread) [supervisor.os.manager] Home Assistant Operating System update failed with: Installation error: Failed updating slot boot.0: failed to run slot hook: Child process exited with code 1

Anything in the Host logs that might be useful for us?

-

System Health information

System Health

version	core-2022.4.0.dev20220228
installation_type	Home Assistant OS
dev	true
hassio	true
docker	true
user	root
virtualenv	false
python_version	3.9.9
os_name	Linux
os_version	5.10.98
arch	x86_64
timezone	Europe/Amsterdam

Home Assistant Supervisor

host_os	Home Assistant OS 7.4
update_channel	dev
supervisor_version	supervisor-2022.02.dev2801
docker_version	20.10.9
disk_total	31.3 GB
disk_used	7.2 GB
healthy	true
supported	true
board	ova
supervisor_api	ok
version_api	ok
installed_addons	File editor (5.3.3), Terminal & SSH (9.3.0), Studio Code Server (4.1.0), Mosquitto broker (6.0.1), Zigbee2mqtt (1.23.0-1)

Lovelace

dashboards	1
resources	0
views	5
mode	storage

Additional information

No response