Proxmox's cloud-init drive is a disk image and requires a storage with
content='images' — the same requirement as the root disk — not the
snippets storage. These are commonly different storages (e.g. 'local'
with content=snippets-only, 'local-zfs' with content=images), and real
Proxmox now creates the VM fine but fails at *start* time with "storage
'X' does not support content-type 'images'" once it tries to generate
the cloud-init ISO.
Found live: a real deployment created the VM successfully, and only
failed when the user started it manually on the Proxmox side.
Christian Manivong
bcadd77420