A typical MapReduce cluster is composed of one master node that runs the JobTracker and a number of slave nodes that run TaskTrackers. The task of managing a MapReduce cluster includes maintaining the health as well as the membership between TaskTrackers and the JobTracker. In this recipe, we will outline commands to manage a MapReduce cluster.
We assume that the Hadoop cluster has been properly configured and running.
Log in to the master node from the cluster administration machine using the following command:
ssh hduser@master
Perform the following steps to manage a MapReduce cluster:
List all the active TaskTrackers using the following command:
hadoop -job -list-active-trackers
Check the status of the JobTracker safe mode using the following command:
hadoop mradmin -safemode get
We will get the following output:
Safe mode is OFF
The output...