Hi Graham,

This is a service-level property of HDFS. The rest endpoint to find it looks like this:

http://<cm_host>:7180/api/v5/clusters/<cluster_name>/services/<hdfs_service_hame>/config?view=full

To modify it using the python api, get a handle to the HDFS service and call hdfs.update_config({"core_site_safety_valve": core_site_safety_valve_value }).

See more on using the python API here:

http://cloudera.github.io/cm_api/docs/python-client/

Thanks,

Darren