We were setting up a small cluster of Hadoop for some requirements, and decided to go with the HortonWorks release of Hadoop. ( HDP 1.1 for Windows ). After installing, we realized that for some reason the Oozie service was not starting up . (we tried both the CLI command provided with the HDP installation, as well as trying to manually start the service via services.msc). Looking through the log files (<HDP 1.1 installation path>\oozie-<version>\Service directory, specifically the oozieservice.out.log file) we found the error - and so realized that Oozie server is dependent on JDK. It does not work with only JRE. To correct this we uninstalled JRE, and installed JDK. We also manually modified the JAVA_HOME environment variable to point to the new installation path. And then Oozie server started working all fine. But all the rest of the services (hadoop jobtracker, hadoop datanode etc.) stopped starting. Checking the logs of the services, we fou...