Couldn't start hadoop datanode normally

Question 1

That simply shows that the datanode tried to startup but took some exception and died.

Please check the datanode log under the logs folder in the hadoop installation folder (unless you changed that config) for exceptions. It usually points to a configuration issue of some kind, esp. network settings (/etc/hosts) related but there are quite a few possibilities.

Question 2

Make sure you are ready with correct configuration and right path. This is a link for Running Hadoop on ubuntu.

I have used this link to setup hadoop in my machine and it works fine.

Question 3

Refer this,

1.Check JAVA_HOME---

    readlink -f $(which java) 
    /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java

2.If JAVA is not available install by command

    sudo apt-get install defalul-jdk

than run 1. and check on terminal

    java -version 
    javac -version

3.Configure SSH

Hadoop requires SSH access to manage its nodes, i.e. remote machines plus your local machine if you want to use Hadoop on it (which is what we want to do in this short tutorial). For our single-node setup of Hadoop, we therefore need to configure SSH access to localhost for the user .

    sudo apt-get install ssh
    sudo su hadoop
    ssh-keygen -t rsa -P “”
    cat $HOME/.ssh/id_rsa.pub >> $HOME/.ssh/authorized_keys
    ssh localhost

Download and extract hadoop-2.7.3(Chosse dirrectory having read write permisson)

Set Environment Variable

    sudo gedit .bashrc
    source .bashrc

Setup Configuration Files

The following files will have to be modified to complete the Hadoop setup:

~/.bashrc   (Already done)
(PATH)/etc/hadoop/hadoop-env.sh 
(PATH)/etc/hadoop/core-site.xml 
(PATH)/etc/hadoop/mapred-site.xml.template 
(PATH)/etc/hadoop/hdfs-site.xm

gedit (PATH)/etc/hadoop/hadoop-env.sh

export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64

gedit (PATH)/etc/hadoop/core-site.xml:

The (HOME)/etc/hadoop/core-site.xml file contains configuration properties that Hadoop uses when starting up. This file can be used to override the default settings that Hadoop starts with.

    ($ sudo mkdir -p /app/hadoop/tmp)

Open the file and enter the following in between the <configuration></configuration> tag:

gedit /usr/local/hadoop/etc/hadoop/core-site.xml 
<configuration> 
 <property> 
  <name>hadoop.tmp.dir</name> 
  <value>/app/hadoop/tmp</value> 
  <description>A base for other temporary directories.</description> 
 </property> 

 <property> 
  <name>fs.default.name</name> 
  <value>hdfs://localhost:54310</value> 
  <description>The name of the default file system.  A URI whose 
  scheme and authority determine the FileSystem implementation.  The 
  uri's scheme determines the config property (fs.SCHEME.impl) naming 
  the FileSystem implementation class.  The uri's authority is used to 
  determine the host, port, etc. for a filesystem.</description> 
 </property> 
</configuration>


(PATH)/etc/hadoop/mapred-site.xml

By default, the (PATH)/etc/hadoop/ folder contains (PATH)/etc/hadoop/mapred-site.xml.template file which has to be renamed/copied with the name mapred-site.xml:

cp /usr/local/hadoop/etc/hadoop/mapred-site.xml.template /usr/local/hadoop/etc/hadoop/mapred-site.xml

The mapred-site.xml file is used to specify which framework is being used for MapReduce.

We need to enter the following content in between the <configuration></configuration> tag:

    <configuration> 
     <property> 
      <name>mapred.job.tracker</name> 
      <value>localhost:54311</value> 
      <description>The host and port that the MapReduce job tracker runs 
      at.  If "local", then jobs are run in-process as a single map 
      and reduce task. 
      </description> 
     </property> 
    </configuration>

(PATH)/etc/hadoop/hdfs-site.xml

The (PATH)/etc/hadoop/hdfs-site.xml file needs to be configured for each host in the cluster that is being used.

It is used to specify the directories which will be used as the namenode and the datanode on that host.

Before editing this file, we need to create two directories which will contain the namenode and the datanode for this Hadoop installation. This can be done using the following commands:

sudo mkdir -p /usr/local/hadoop_store/hdfs/namenode 
sudo mkdir -p /usr/local/hadoop_store/hdfs/datanode

Open the file and enter the following content in between the <configuration></configuration> tag:

    gedit (PATH)/etc/hadoop/hdfs-site.xml 

    <configuration> 
     <property> 
      <name>dfs.replication</name> 
      <value>1</value> 
      <description>Default block replication. 
      The actual number of replications can be specified when the file is created. 
      The default is used if replication is not specified in create time. 
      </description> 
     </property> 
     <property> 
       <name>dfs.namenode.name.dir</name> 
       <value>file:/usr/local/hadoop_store/hdfs/namenode</value> 
     </property> 
     <property> 
       <name>dfs.datanode.data.dir</name> 
       <value>file:/usr/local/hadoop_store/hdfs/datanode</value> 
     </property> 
    </configuration>

Format the New Hadoop Filesystem

Now, the Hadoop file system needs to be formatted so that we can start to use it. The format command should be issued with write permission since it creates current directory under /usr/local/hadoop_store/ folder:

    bin/hadoop namenode -format

or

    bin/hdfs namenode -format

HADOOP SETUP IS DONE

Now start the hdfs

start-dfs.sh
start-yarn.sh

CHECK URL: http://localhost:50070/

FOR STOPPING HDFS

stop-dfs.sh
stop-yarn.sh