I downloaded: spark-2.1.0-bin-hadoop2.7.tgz from http://spark.apache.org/downloads.html. I have Hadoop HDFS and YARN started with $ start-dfs.sh and
I found the solution from another Stackoverflow question. It was not about configuring Apache Spark, it was about configuring Hadoop YARN:
Running yarn with spark not working with Java 8
Make sure your yarn-site.xml, from your Hadoop configuration folder, has these properties:
yarn.nodemanager.pmem-check-enabled
false
yarn.nodemanager.vmem-check-enabled
false