2.3. 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 a 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.

	Note
	configs.sh creates temporary files. We recommended that you run configs.sh as root or as a user having write permission on the local folder.

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 3.3. 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.