Hadoop - namenode is not starting up

I am trying to run hadoop as a root user, i executed namenode format command hadoop namenode -format when the Hadoop file system is running.

After this, when i try to start the name node server, it shows error like below

13/05/23 04:11:37 ERROR namenode.FSNamesystem: FSNamesystem initialization failed.
java.io.IOException: NameNode is not formatted.
        at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:330)
        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.loadFSImage(FSDirectory.java:100)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initialize(FSNamesystem.java:411)

I tried to search for any solution, but cannot find any clear solution.

Can anyone suggest?

Thanks.

Cool, i have found the solution.

Stop all running server

1) stop-all.sh 

Edit the file /usr/local/hadoop/conf/hdfs-site.xml and add below configuration if its missing

<property>
    <name>dfs.data.dir</name>
    <value>/app/hadoop/tmp/dfs/name/data</value> 
    <final>true</final> 
    </property> 
    <property> 
    <name>dfs.name.dir</name>
    <value>/app/hadoop/tmp/dfs/name</value> 
    <final>true</final> 
</property>

Start both HDFS and MapReduce Daemons

2) start-dfs.sh
3) start-mapred.sh

Then now run the rest of the steps to run the map reduce sample given in this link

Note : You should be running the command bin/start-all.sh if the direct command is not running.