Unable to start a node manager on master

Question

I am setting up a Hadoop YARN cluster and I am using a machine as both a master and a slave. When I start the YARN using the following command, it starts the nodemanager on

Answer 1

Above error means, you are trying to start a process on 8040, which is already occupied by another instance.

To get rid of this error, you need to kill the process which is currently listening to port 8040. Your lsof output says pid is 28021. kill the process using the following command and start again

kill -9 28021