Note:

Use the service command to start, stop, and restart CDH components, instead of 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).

  Note:

From the Apache ZooKeeper site:

ZooKeeper is a high-performance coordination service for distributed applications. It exposes common services — such as naming, configuration management, synchronization, and group services - in a simple interface so you do not have to write them from scratch. You can use it off-the-shelf to implement consensus, group management, leader election, and presence protocols. And you can build on it for your own, specific needs.

To learn more about Apache ZooKeeper, visit http://zookeeper.apache.org/.

  Note:

To see which version of ZooKeeper is shipping in CDH 5, check the CDH Version and Packaging Information. For important information on new and changed components, see the Cloudera Release Guide.