Restarting Hadoop Namenode when you have java exceptions

Occasionally, accumulated log files could create disk full errors, which stops Hadoop's Namenode daemon. While resolving this,

1. Create available space, perhaps delete or back-up logs.
2. After that, execute $HADOOP_HOME/bin/hadoop-daemon.sh start namenode
1. Confirm that namenode daemon continues to run even after some seconds later, i.e., 20 seconds.
2. If yes, you are good.
3. If no, you might have one of those situations:
• Namenode Null Pointer exception
• namenode number format exception
4. If you have the above exceptions, 
1. Go to your directory for dfs.name.dir in your hdfs-site.xml or by default it is /dfs/name/current
2. $printf "\xff\xff\xff\xee\xff" > edits
3. if you have edits.new, then $printf "\xff\xff\xff\xee\xff" > edits.new
5. Go to the step 2. Check your namenode work.