Firstly, use the jps command to check the daemons that are running in the cluster.
To know the report of your HDFS daemons, you can execute this command:
bin/hdfs dfsadmin -report
Try to execute these commands:
hdfs getconf -namenodes
hdfs getconf -secondaryNamenodes
.. .. .. ..
If you want to know more about Hadoop, then do check out the following video tutorial: