Cloudera Manager supports Oracle JDK 1.7.0_55 when it's managing CDH 5.x and Oracle JDK 1.6.0_31 and 1.7.0_55 when it's managing CDH 4.x. Cloudera Manager supports Oracle JDK 1.7.0_55 when it's managing both CDH 4.x and CDH 5.x clusters. Oracle JDK 1.6.0_31 and 1.7.0_55 can be installed during the installation and upgrade. For further information, see Java Development Kit Installation.

Cloudera Manager requires several databases. The Cloudera Manager Server stores information about configured services, role assignments, configuration history, commands, users, and running processes in a database of its own. You must also specify a database for the Activity Monitor and Reports Manager management services.

The database you choose to use must be configured to support UTF8 character set encoding. The embedded PostgreSQL database that is installed when you follow Installation Path A - Automated Installation by Cloudera Manager automatically provides UTF8 encoding. If you install a custom database, you may need to enable UTF8 encoding. The commands for enabling UTF8 encoding are described in each database's section under Cloudera Manager and Managed Service Databases.

After installing a database, upgrade to the latest patch version and apply any other appropriate updates. The available updates may be specific to the operating system on which it is installed.

For information about the databases supported by CDH, see CDH 4 Supported Databases and CDH 5 Supported Databases.

• Cluster hosts must have a working network name resolution system and correctly formatted /etc/hosts file. All cluster hosts must have properly configured forward and reverse host resolution through DNS. The /etc/hosts files must contain consistent information about host names and addresses across all hosts. A properly formatted /etc/hosts should be similar to the following example:

  127.0.0.1 localhost.localdomain localhost
  192.168.1.1 cluster-01.example.com cluster-01
  192.168.1.2 cluster-02.example.com cluster-02
  192.168.1.3 cluster-03.example.com cluster-03 

  The /etc/hosts file must not have duplicate IP addresses.
• In most cases, the Cloudera Manager Server must have SSH access to the cluster hosts when you run the installation or upgrade wizard. You must log in using a root account or an account that has password-less sudo permission. For authentication during the installation and upgrade procedures, you must either enter the password or upload a public and private key pair for the root or sudo user account. If you want to use a public and private key pair, the public key must be installed on the cluster hosts before you use Cloudera Manager.

  Cloudera Manager uses SSH only during the initial install or upgrade. Once your cluster is set up, you can disable root SSH access or change the root password. Cloudera Manager does not save SSH credentials and all credential information is discarded once the installation is complete. For further information, see Permission Requirements.

• The Cloudera Manager Agent runs as root so that it can make sure the required directories are created and that processes and files are owned by the appropriate user (for example, the hdfs and mapred users).
• No blocking by Security-Enhanced Linux (SELinux).
• Disable Ipv6 on all hosts.
• No blocking by iptables or firewalls; make sure port 7180 is open because it is the port used to access Cloudera Manager after installation. Cloudera Manager communicates using specific ports, which must be open. See Configuring Ports for Cloudera Manager.
• For RedHat and CentOS, make sure the/etc/sysconfig/network file on each system contains the hostname you have just set (or verified) for that system.
• Cloudera Manager and CDH use several user accounts and groups to complete their tasks. The set of user accounts and groups varies according to which components you choose to install. Do not delete these accounts or groups and do not modify their permissions and rights. Ensure no existing systems obstruct the functioning of these accounts and groups. For example, if you have scripts that delete user accounts not in a white-list, add these accounts to the list of permitted accounts. Cloudera Manager, CDH, and managed services create and use the following accounts and groups:

  Account	Type	Product
  cloudera-scm	User and group	Cloudera Manager
  flume	User and group	CDH 4, CDH 5
  hadoop	Group	CDH 4, CDH 5
  hbase	User and group	CDH 4, CDH 5
  hdfs	User and group. Must also be a member of the hadoop group.	CDH 4, CDH 5
  hive	User and group	CDH 4, CDH 5
  httpfs	User and group	CDH 4, CDH 5
  hue	User and group	CDH 4, CDH 5
  impala	User and group. Must also be member of the hdfs and hive groups.	CDH 4.1 or later, CDH 5
  llama	User and group	CDH 5
  mapred	User and group. Must also be a member of the hadoop group.	CDH 4, CDH 5
  oozie	User and group	CDH 4, CDH 5
  solr	User and group	CDH 4.3 and later, CDH 5
  spark	User and group	Spark, CDH 5
  sqoop	User and group	CDH 4, CDH 5
  sqoop2	User. Must be member of the sqoop group.	CDH 4.2 and later, CDH 5
  yarn	User and group	CDH 4, CDH 5
  zookeeper	User and group	CDH 4, CDH 5