nly.  If this field is set to IfPossible, the mount is made
recursively read-only, if it is supported by the container runtime.  If this
field is set to Enabled, the mount is made recursively read-only if it is
supported by the container runtime, otherwise the pod will not be started and
an error will be generated to indicate the reason.

If this field is set to IfPossible or Enabled, MountPropagation must be set to
None (or be unspecified, which defaults to None).

If this field is not specified, it is treated as an equivalent of Disabled.²