I installed a three 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 : 2016-06-18 21:23:53,980 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: namenode/192.168.1.100:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) 2016-06-18 21:23:55,029 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: namenode/192.168.1.100:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) 2016-06-18 21:23:56,030 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: namenode/192.168.1.100:9000. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) 2016-06-18 21:23:57,031 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: namenode/192.168.1.100:9000. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) 2016-06-18 21:23:58,032 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: namenode/192.168.1.100:9000. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS) namenode machine's infomation: cat /etc/hosts #127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 #::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.1.100 namenode 192.168.1.101 datanode1 192.168.1.102 datanode2 cat /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 IPV6INIT=yes BOOTPROTO=dhcp UUID=61fe61d3-fcda-4fed-ba81-bfa767e0270a ONBOOT=yes TYPE=Ethernet DEFROUTE=yes PEERDNS=yes PEERROUTES=yes IPV4_FAILURE_FATAL=no IPV6_AUTOCONF=yes IPV6_DEFROUTE=yes IPV6_PEERDNS=yes IPV6_PEERROUTES=yes IPV6_FAILURE_FATAL=no NAME="System eth0" BOOTPROTO="static" ONBOOT="yes" IPADDR=192.168.1.100 GATEWAY=192.168.1.1 NETMASK=255.255.255.0 DNS1=192.168.1.1 cat /etc/hostname namenode cat core-site.xml <configuration> <property> <name>hadoop.tmp.dir</name> <value>/home/hadoop/tmp</value> <description>Abase for other temporary directories.</description> </property> <property> <name>fs.defaultFS</name> <value>hdfs://namenode:9000</value> </property> <property> <name>io.file.buffer.size</name> <value>4096</value> </property> cat hdfs-site.xml <configuration> <property> <name>dfs.nameservices</name> <value>hadoop-cluster1</value> </property> <property> <name>dfs.namenode.secondary.http-address</name> <value>namenode:50090</value> </property> <property> <name>dfs.namenode.name.dir</name> <value>file:///home/hadoop/dfs/name</value> </property> <property> <name>dfs.datanode.data.dir</name> <value>file:///home/hadoop/dfs/data</value> </property> <property> <name>dfs.replication</name> <value>2</value> </property> <property> <name>dfs.webhdfs.enabled</name> <value>true</value> </property> cat mapred-site.xml <configuration> <property> <name>mapreduce.framework.name</name> <value>yarn</value> </property> <property> <name>mapreduce.jobtracker.http.address</name> <value>namenode:50030</value> </property> <property> <name>mapreduce.jobhistory.address</name> <value>namenode:10020</value> </property> <property> <name>mapreduce.jobhistory.webapp.address</name> <value>namenode:19888</value> </property> cat yarn-site.xml <configuration> <property> <name>yarn.nodemanager.aux-services</name> <value>mapreduce_shuffle</value> </property> <property> <name>yarn.resourcemanager.address</name> <value>namenode:8032</value> </property> <property> <name>yarn.resourcemanager.scheduler.address</name> <value>namenode:8030</value> </property> <property> <name>yarn.resourcemanager.resource-tracker.address</name> <value>namenode:8031</value> </property> <property> <name>yarn.resourcemanager.admin.address</name> <value>namenode:8033</value> </property> <property> <name>yarn.resourcemanager.webapp.address</name> <value>namenode:8088</value> </property> cat slaves datanode1 datanode2 ... View more