using SeedImage this would be:

apiVersion: <http://elemental.cattle.io/v1beta1|elemental.cattle.io/v1beta1>

kind: SeedImage

metadata:

name: training-elemental3-seedimage

namespace: fleet-default

spec:

baseImage: <http://registry.suse.com/suse/sle-micro-iso/5.5:2.0.2|registry.suse.com/suse/sle-micro-iso/5.5:2.0.2>

registrationRef:

apiVersion: <http://elemental.cattle.io/v1beta1|elemental.cattle.io/v1beta1>

kind: MachineRegistration

name: training-elemental3

namespace: fleet-default

cloud-config:

runcmd:

- hostnamectl set-hostname $(vmtoolsd --cmd "info-get guestinfo.hostname")