Spark uses Hadoop client libraries for HDFS and YARN. Starting in version Spark 1.4, the project packages "Hadoop free" builds that lets you more easily connect a single Spark binary to any Hadoop version. To use these builds, you need to modify `SPARK_DIST_CLASSPATH` to include Hadoop's package jars. The most convenient place to do this is by adding an entry in `conf/spark-env.sh`.
This page describes how to connect Spark to Hadoop for different types of distributions.
# Apache Hadoop
For Apache distributions, you can use Hadoop's 'classpath' command. For instance: