hr4757@c201-116:~$ hadoop dfsadmin -report
11/02/23 10:39:32 INFO ipc.Client: Retrying connect to server: c201-116/129.114.19.21:9000. Already tried 0 time(s).
11/02/23 10:39:33 INFO ipc.Client: Retrying connect to server: c201-116/129.114.19.21:9000. Already tried 1 time(s).
This error message simply means longhorn could not run Hadoop. It may be due to memory problem.
SSH to the master namenode and run fix_HDFS. Here's how to.