Name node or Data node not starting

If you come across these problems :

Data node not starting :

          Solution you can try :

              1.  "chown" of hdfs folderr to the current user

              2.  " chmod" of hdfs folder to 755 to the current user

              3.  delete the hdfs folder and reformat (hadoop namenode -format) if 1 and 2 does not work

     Note : Problem with data node generally occurs due to file permission.

Name node not starting

          Solution you can try:

               1. Comment out or remove the entry 127.0.1.1

               2. Check your ip/dns setting, name node problem generally related to domain/IP

              3. Also check if you name/IP you are specifying in the hadoop setting xml can be resolved. you can do this bye pinging/ or telnetting the IP/Domain you have specified for the hadoop settings.

     Note : Problem related to name node generally occurs due to domain/IP related problems.