Problem Scenario
You run an HDFS command, but you get this message: "ERROR: Hadoop common not found"
What should you do?
Solution
As the hduser or user that runs hdfs, log in. Run echo $HADOOP_HOME
That directory should have a libexec directory with a file called hadoop-config.sh.
Run this: ls -lh $HADOOP_HOME/libexec
One way to create it is this: 1) find a hadoop-config.sh file (e.g., with a sudo find / -name hdfs-config.sh command). 2) run this command sudo ln -s /path/to/hdfs-config.sh $HADOOP_HOME/libexec/hadoop-config.sh
Be mindful of the "hadoop-config.sh" and "hdfs-config.sh" difference; it is subtle.