Also in /tmp/custom-spark.conf you can see its set ;

root@0126-125139-sxrs37zl-10-215-1-5:/databricks/driver# cat /tmp/custom-spark.conf

...

spark.master local[*, 4]

spark.databricks.passthrough.enabled true

spark.databricks.cloudfetch.hasRegionSupport true

spark.databricks.daemon.driver.startJDBC false