Description of problem:

If the readOnlyRootFilesystem flag is set to true for the machine-os-images container in CBO, it will fail deployment because the copy-metal script writes to /coreos directory, which is readOnly, during runtime - https://github.com/openshift/machine-os-images/blob/03609a989d93de635d03fff886afeffe150dc9a3/scripts/copy-metal#L43

Fix:
Use the writable /shared/html/images directory to write files during runtime.