I installed a 2 node hadoop cluster. The master and slave node starts separately but the datanode isn't shown in namenode webUI. The log file for datanode shows the following error : 2016-02-09 23:30:53,920 INFO org.apache.hadoop.ipc.Server: IPC Server Responder: starting 2016-02-09 23:30:53,920 INFO org.apache.hadoop.ipc.Server: IPC Server listener on 50020: starting 2016-02-09 23:30:54,976 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hadoop-master/172.17.25.5:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) 2016-02-09 23:30:55,977 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hadoop-master/172.17.25.5:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) 2016-02-09 23:21:15,062 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server: hadoop-master/172.17.25.5:9000 The hosts file in slave is 172.17.25.5 hadoop-master 127.0.0.1 silp-ProLiant-DL360-Gen9 172.17.25.18 hadoop-slave-1 # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters the core-site.xml file is : <configuration> <property> <name>fs.default.name</name> <value>hdfs://hadoop-master:9000</value> </property> <property> <name>dfs.permissions</name> <value>false</value> </property> </configuration> Kindly help with this issue. ... View more