5.3. Start YARN/MapReduce Services

To start YARN, run commands as a YARN user. To start MapReduce, run commands as a MapReduce user.

If you have a secure cluster, create the following principals and keytabs for YARN before you start the YARN service:

yarn.resourcemanager.principal
yarn.resourcemanager.keytab
yarn.nodemanager.principal
yarn.nodemanager.keytab
yarn.resourcemanager.webapp.spnego-principal
yarn.nodemanager.webapp.spnego-principal
mapreduce.jobhistory.webapp.spnego-principal
yarn.resourcemanager.webapp.spnego-keytab-file
yarn.nodemanager.webapp.spnego-keytab-file
mapreduce.jobhistory.webapp.spnego-keytab-file

Start the ResourceManager on your previous JobTracker host.

su $YARN_USER
export HADOOP_LIBEXEC_DIR=/usr/lib/hadoop/libexec
/usr/lib/hadoop-yarn/sbin/yarn-daemon.sh start resourcemanager
ps -ef | grep -i resourcemanager

Prepare the NodeManager hosts.
1. Change permissions for /usr/lib/hadoop-yarn/bin/container-executor.cfg
```
chown yarn:hadoop /usr/lib/hadoop-yarn/bin/container-executor
chmod -R 650 /usr/lib/hadoop-yarn/bin/container-executor
```
2. On all NodeManager hosts, add the yarn user to the hadoop group.
  For example if you are using CentOS6:
```
usermod -a -G hadoop yarn
```

Start the NodeManager on your previous TaskTracker hosts.

su $YARN_USER
export HADOOP_LIBEXEC_DIR=/usr/lib/hadoop/libexec
/usr/lib/hadoop-yarn/sbin/yarn-daemon.sh start nodemanager
ps -ef | grep -i nodemanager

To start MapReduce, run the following commands as MapReduce user:

su $MAPREDUCE_USER
export HADOOP_LIBEXEC_DIR=/usr/lib/hadoop/libexec
/usr/lib/hadoop-mapreduce/sbin/mr-jobhistory-daemon.sh --config /etc/hadoop/conf start historyserver
ps -ef | grep -i jobhistoryserver

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