What are the Hadoop Daemons

  • Hadoop has 5 daemons.They are NameNode, DataNode, Secondary NameNode, JobTracker and TaskTracker.
  • NameNode
    It stores the Meta Data about the data that are stored in DataNodes.
  • DataNode
    It stores the actual Data.
  • Secondary NameNode
    It is the backup of namenode and it just contains entire metadata of data nodes like data node address, properties and block report of each data node.
  • JobTracker
    Job Tracker is a master which creates and runs the job. JobTracker that runs on name node, allocates the job to TaskTrackers.
  • TaskTracker
    TaskTracker is a slave and runs on data node. TaskTracker runs the tasks and reports the status of task to JobTracker.