This is the documentation for Cloudera Enterprise 5.8.x. Documentation for other versions is available at Cloudera Documentation.

Before You Install CDH 5 on a Cluster

  Important:

  • Use the service command to start, stop, and restart CDH components, rather than running scripts in /etc/init.d directly. The service command creates a predictable environment by setting the current working directory to / and removing most environment variables (passing only LANG and TERM). With /etc/init.d, existing environment variables remain in force and can produce unpredictable results. When you install CDH from packages, service is installed as part of the Linux Standard Base (LSB).

  • Upgrading from CDH 4: If you are upgrading from CDH 4, you must first uninstall CDH 4, then install CDH 5; see Upgrading from CDH 4 to CDH 5.

  • On SLES 11 platforms, do not install or try to use the IBM Java version bundled with the SLES distribution; Hadoop will not run correctly with that version. Install the Oracle JDK following directions under Java Development Kit Installation.

  • If you are migrating from MapReduce v1 (MRv1) to MapReduce v2 (MRv2, YARN), see Migrating from MapReduce (MRv1) to MapReduce (MRv2) for important information and instructions.

Before you install CDH 5 on a cluster, there are some important steps you need to do to prepare your system:

  1. Verify you are using a supported operating system for CDH 5. See CDH 5 Requirements and Supported Versions.
  2. If you haven't already done so, install the Oracle Java Development Kit. For instructions and recommendations, see Java Development Kit Installation.

Scheduler Defaults

Note the following differences between MRv1 (MapReduce) and MRv2 (YARN).

  • MRv1 (MapReduce v1):
    • Cloudera Manager and CDH 5 set the default to FIFO.
    FIFO is set as the default for backward-compatibility purposes, but Cloudera recommends Fair Scheduler. Capacity Scheduler is also available.
  • MRv2 (YARN):
    • Cloudera Manager and CDH 5 set the default to Fair Scheduler.
    Cloudera recommends Fair Scheduler because Impala and Llama are optimized for it. FIFO and Capacity Scheduler are also available.

High Availability

In CDH 5 you can configure high availability both for the NameNode and the JobTracker or Resource Manager.
Page generated July 8, 2016.