Review feedback for spark env file

Author: pwendell

conf/spark-env.sh.template

@@ -12,9 +12,9 @@
 # Options read by executors and drivers running inside the cluster
 # - SPARK_LOCAL_IP, to set the IP address Spark binds to on this node
 # - SPARK_PUBLIC_DNS, to set the public DNS name of the driver program
+# - SPARK_CLASSPATH, default classpath entries to append
 # - SPARK_LOCAL_DIRS, shuffle directories to use on this node
 # - MESOS_NATIVE_LIBRARY, to point to your libmesos.so if you use Mesos
-# - SPARK_CLASSPATH, default classpath entries to append
 
 # Options read in YARN client mode
 # - SPARK_YARN_APP_JAR, Path to your application’s JAR file (required)
@@ -30,10 +30,13 @@
 # Options for the daemons used in the standalone deploy mode:
 # - SPARK_MASTER_IP, to bind the master to a different IP address or hostname
 # - SPARK_MASTER_PORT / SPARK_MASTER_WEBUI_PORT, to use non-default ports
-# - SPARK_MASTER_OPTS, to set config properties at the master (e.g "-Dx=y")
+# - SPARK_MASTER_OPTS, to set config properties only for the master (e.g. "-Dx=y")
 # - SPARK_WORKER_CORES, to set the number of cores to use on this machine
-# - SPARK_WORKER_MEMORY, to set how much memory to use (e.g. 1000m, 2g)
+# - SPARK_WORKER_MEMORY, to set how much total memory to workers have to give executors (e.g. 1000m, 2g)
 # - SPARK_WORKER_PORT / SPARK_WORKER_WEBUI_PORT
 # - SPARK_WORKER_INSTANCES, to set the number of worker processes per node
 # - SPARK_WORKER_DIR, to set the working directory of worker processes
-# - SPARK_PUBLIC_DNS, to set the public dns name of the master
+# - SPARK_WORKER_OPTS, to set config properties only for the worker (e.g. "-Dx=y")
+# - SPARK_HISTORY_OPTS, to set config properties only for the history server (e.g. "-Dx=y")
+# - SPARK_DAEMON_OPTS, to set config properties for all daemons (e.g. "-Dx=y")
+# - SPARK_PUBLIC_DNS, to set the public dns name of the master or workers