If mapreduce jobs are not possible to run, issue with yarn because of less ram

If mapreduce jobs are not possible to run, issue with yarn because of less ram . 

update "yarn-site.xml" with below properties and restart "yarn"

<property>
<name>yarn.scheduler.minimum-allocation-mb</name>
<value>512</value>
</property>
<property>
<name>yarn.scheduler.maximum-allocation-mb</name>
<value>2048</value>
</property>
<property>
<name>yarn.nodemanager.resource.memory-mb</name>
<value>20480</value>
</property>

How to change the hostname in ubuntu

1. open "/etc/hostname" file using text editor
2. command: sudo gedit /etc/hostname
3. modify the existing hostname value with new
4. open "/etc/hosts" file using text editor
5. command:  sudo gedit /etc/hosts
6. modify the existing hostname value with new
7. execute below command to refresh the hostname
8. command: sudo service hostname restart