Hadoop : Starting Datanode doesn't seem to respond - hadoop

Question

My testing environment
I'm trying to deploy into my testing environment an Hadoop Cluster based on 3 nodes :
1 Namenode (master : 172.30.10.64)
2 Datanodes (slave1 : 172.30.10.72 and slave2 : 172.30.10.62)
I configured files with master properties into my namenode and with slaves properties into my datananodes.
Master's files
Hosts :
127.0.0.1 localhost
172.30.10.64 master
172.30.10.62 slave2
172.30.10.72 slave1
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
hdfs-site.xml :
<configuration>
<property>
<name>dfs.replication</name>
<value>2</value>
</property>
<property>
<name>dfs.namenode.name.dir</name>
<value>file:/usr/local/hadoop_tmp/hdfs/namenode</value>
</property>
</configuration>
core-site.xml :
<configuration>
<property>
<name>fs.default.name</name>
<value>hdfs://master:9000</value>
</property>
</configuration>
yarn-site.xml :
<configuration>
<property>
<name>yarn.resourcemanager.resource-tracker.address</name>
<value>master:8025</value>
</property>
<property>
<name>yarn.resourcemanager.scheduler.address</name>
<value>master:8030</value>
</property>
<property>
<name>yarn.resourcemanager.address</name>
<value>master:8050</value>
</property>
</configuration>
mapred-site.xml :
<configuration>
<property>
<name>mapreduce.framework.name</name>
<value>yarn</value>
</property>
<property>
<name>mapreduce.jobhistory.address</name>
<value>master:10020</value>
</property>
</configuration>
And I have slaves file :
slave1
slave2
masters file :
master
Slaves' files :
I added just files which changed against master's files.
hdfs-site.xml :
<configuration>
<property>
<name>dfs.replication</name>
<value>2</value>
</property>
<property>
<name>dfs.datanode.data.dir</name>
<value>file:/usr/local/hadoop_tmp/hdfs/datanode</value>
</property>
</configuration>
My issue
I launched from /usr/local/hadoop/sbin :
./start-dfs.sh && ./start-yarn.sh
This is what I get :
hduser#master:/usr/local/hadoop/sbin$ ./start-dfs.sh && ./start-yarn.sh
18/03/14 10:45:50 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Starting namenodes on [master]
hduser#master's password:
master: starting namenode, logging to /usr/local/hadoop-2.7.5/logs/hadoop-hduser-namenode-master.out
hduser#slave2's password: hduser#slave1's password:
slave2: starting datanode, logging to /usr/local/hadoop-2.7.5/logs/hadoop-hduser-datanode-slave2.out
So I opened log file from my slave2 :
2018-03-14 10:46:05,494 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/172.30.10.64:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECOND$
2018-03-14 10:46:06,495 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/172.30.10.64:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECOND$
2018-03-14 10:46:07,496 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/172.30.10.64:9000. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECOND$
What I've done
I tried some things but none effects up to now :
ping from master to slaves and between slaves works fine
ssh from master to slaves and between slaves works fine
hdfs namenode -format in my master node
Recreate Namenode and Datanaode folders
Open port 9000 in my master VM
Firewall is disabled : sudo ufw status --> disabled
I'm a bit lost because all seems to be ok and I don't know why I don't overcome to start my hadoop cluster.

Answer 1

I maybe find the answer :
I regenerate ssh key from master node and then copy to slave nodes. It seems to work now.
#Generate a ssh key for hduser
$ ssh-keygen -t rsa -P ""
#Authorize the key to enable password less ssh
$ cat /home/hduser/.ssh/id_rsa.pub >> /home/hduser/.ssh/authorized_keys
$ chmod 600 authorized_keys
#Copy this key to slave1 to enable password less ssh and slave2 too
$ ssh-copy-id -i ~/.ssh/id_rsa.pub slave1
$ ssh-copy-id -i ~/.ssh/id_rsa.pub slave2