Starting/Stoping Hadoop and HBase in order

Hadoop Startup Process

Namenode  -->  Datanodes  -->  SecondaryNamenode  -->  JobTracker  -->  TaskTrackers

Hadoop Shutdown Process
JobTracker  -->  TaskTracker  --> Namenode  -->  Datanodes  --> SecondaryNamenode

HBase Startup Process

Zookeepers  -->  HMaster  -->  RegionServers

HBase Shutdown Process

RegionServers  -->  HMaster  -->  Zookeepers

Too many fetch-failures, hadoop mapreduce job, hadoop mapreduce Too many fetch-failures

This may happen due to following reasons:

1. Wrong DNS Entry, Hosts file entries, 

Description:

Nodes are not able to communicate with each other, so check if nodes where this error comes you can ping or  nslookup to that node

2. Tasktracker http thread

Description:

Check of the value of this tag in mapreduce-site.xml, if it is lower make it somewhat higer around 100.

Get Directory path from a file path/Get file name from a filepath in shell Linux/Unix

Get Directory path from a file path.

Command : 

dirname /path/path1/filename

Output :

 /path/path

Get filename from a filepath

Command:

basename /path/path/filename

Output:

filaname