Hadoop uses SSH keys to securely communicate between the components. The SSH key should be created on the control machine and then securely uploaded to the target machines. For example, to create a SSH key, run
ssh-keygen -P '' and then use
hadoop_id_rsa as the name when prompted. The
HADOOP_ID_RSA variable should be the path to this newly created key. Be sure to exclude this key with
.dockerignore, or save it outside of your playbook repo. By default the variable points to
secret/hadoop_id_rsa and Ansible will test the path directly under the playbook file.
If installing a unified Hadoop instance for Accumulo or other big data applications, be sure to provision Zookeeper first. Many big data applications don't package their own Zookeeper JARs and require zookeeper to be installed on every node, even if zookeeper is disabled. For example, your playbook should look something like this:
... roles: - ansible-java-ubuntu - ansible-zookeeper-ubuntu - ansible-hadoop-ubuntu ...
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