java.lang.NullPointerException
  at org.apache.cassandra.config.DatabaseDescriptor.getDiskFailurePolicy(DatabaseDescriptor.java:1877)
  at org.apache.cassandra.utils.JVMStabilityInspector.inspectThrowable(JVMStabilityInspector.java:62)
  at org.apache.cassandra.io.util.FileUtils.<clinit>(FileUtils.java:79)
  at org.apache.cassandra.utils.FBUtilities.getToolsOutputDirectory(FBUtilities.java:807)
  at org.apache.cassandra.tools.NodeTool.printHistory(NodeTool.java:199)
  at org.apache.cassandra.tools.NodeTool.main(NodeTool.java:167)

./nodetool help