NameNode is failing to start

[Dustine Rene Bernasor]

Hello,

I was installing Ambari 1.2.1. When I reach step 9, after the services 
are installed,
NameNode cannot be started.
The ff. exception appeared in the log

2013-03-14 10:58:00,426 ERROR
org.apache.hadoop.hdfs.server.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)
        at 
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:379)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:287)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:548)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1431)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1440)
2013-03-14 10:58:00,427 ERROR
org.apache.hadoop.hdfs.server.namenode.NameNode: 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)
        at 
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:379)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:287)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:548)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1431)
        at 
org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1440)

2013-03-14 10:58:00,428 INFO
org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at Crawler51.localdomain.com/192.168.3.51
************************************************************/

Thanks.

Dustine