hdfs datanode in docker

docker run -e HDFS_NAMENODE_RPC_HOST=$NAMENODEHOST -v /data:/var/hdfs/datanode --net=host --name hdfs-dn -d dataman/hdfs-datanode:2.7.1

• TCP 50010 dfs.datanode.address port for data transfer
• TCP 50020 dfs.datanode.ipc.address ipc server
• TCP 50075 dfs.datanode.http.address http server
• TCP 50475 dfs.datanode.https.address https server

Q1: Tab Overview is giving me 3 living datanodes on namenode webpage, while tab Datanodes is showing 1 living datanode only.Why?

A1. Plz make sure your datanode servers have the different hostname