Basically, SPARK_CONF_DIR hosts all the user specific configuration files, e.g.
spark-defaults.conf - containing all the spark properties.
log4j.properties - Logger configuration.
core-site.xml - Hadoop related configuration.
fairscheduler.xml - Spark's fair scheduling policy at the job level.
metrics.properties - Spark metrics.
Any user specific - library or framework specific configuration file.
I wanted to know, how the users of spark on k8s, propagate these configurations to the spark driver in cluster mode? and what if some configuration needs to be picked by executors (e.g. HDFS core-site.xml etc...)