4.3. Add YARN/MR2 and Update Configurations

Start the Ambari Server. On the Server host:

ambari-server start

Start each Ambari Agent. On all Agent hosts:

ambari-agent start

After the Server and all Agents are running, log into Ambari Web. Do a hard refresh on your browser to make sure you are displaying the updated GUI. Make sure all hosts are healthy and all services are in Stopped state.

Add YARN and MapReduce2 services:

If you are not already there, go to the Upgrade Folder.
Execute the add-yarn-mr2 action:
```
python UpgradeHelper_HDP2.py --hostname $HOSTNAME --user $USERNAME --password $PASSWORD --clustername $CLUSTERNAME add-yarn-mr2
```
If desired, you can use the -n option to see the API calls as they are being made so that you can verify them.

Update the respective configurations:

If you are not already there, go to the Upgrade Folder.

Execute the update-configs action:

python UpgradeHelper_HDP2.py --hostname $HOSTNAME --user $USERNAME --password $PASSWORD --clustername $CLUSTERNAME update-configs

Update individual configuration settings as needed. On the Ambari Server, use /var/lib/ambari-server/resources/scripts/configs.sh to inspect and update the configuration properties.

Get configuration details:

configs.sh get $HOSTNAME $CLUSTERNAME $CONFIGURATION-TYPE

For example:
configs.sh get localhost myclustername global

Evaluate each property value returned and modify as needed:

configs.sh set $HOSTNAME $CLUSTERNAME $CONFIGURATION-TYPE "property name" "new value"

For example:
configs.sh set localhost myclustername global yarn_log_dir_prefix “/apps/logs/yarn”

Remove properties that are not needed:

configs.sh delete $HOSTNAME $CLUSTERNAME $CONFIGURATION-TYPE "property name"

For example:
configs.sh delete localhost myclustername global dfs.client-write-packet-size

Table II.6.1. Key Properties to Check
Configuration Type	Property	Description
global	yarn_log_dir_prefix	The location for the YARN logs
global	yarn_pid_dir_prefix	The location for the YARN pid files
global	yarn_user	The YARN user
-	-	-
yarn-site	yarn.nodemanager.local-dirs	The location for container logs
yarn-site	yarn.nodemanager.log-dirs	The directories for localized files

	Note
	Make any necessary modifications before starting the services.

Install the YARN and MapReduce2 services:

If you are not already there, go to the Upgrade Folder.

Execute the install-yarn-mr2 action:

python UpgradeHelper_HDP2.py --hostname $HOSTNAME --user $USERNAME --password $PASSWORD --clustername $CLUSTERNAME install-yarn-mr2

	Note
	This is a two step process. You can use the Ambari Web GUI to monitor the progress. Both steps must be complete before you continue to the next step.