Alright. Thanks to @RemcoBuddelmeijer and @maxb the migration was successful.
It’s important to shutdown the Vault server indeed. I mounted the two PVC’s to a manually created pod with the Vault agent image and added the following command in the Kubernetes manifest:
command:
- /usr/local/bin/docker-entrypoint.sh
- sleep
- 999d
Thanks to this command the Vault server won’t start, according to @maxb.