Disable SSH Server If Possible

---
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: master
  name: 75-master-sshd-disable
spec:
  config:
    ignition:
      version: 3.1.0
    systemd:
      units:
      - enabled: false
        name: sshd.service

This will disable the sshd service in all the nodes labeled with the "master" role.

Note that this needs to be done for each MachineConfigPool

For more information on how to configure nodes with the Machine Config Operator see the relevant documentation.