7.6. Downgrade the MapReduce JobHistoryServer

	Note
	Retain the newer versions of MapReduce tarballs and auxiliary jars on HDFS until all jobs using them have completed on the cluster.

Shut down the JobHistoryServer process, switch to the previous version, and start the process:

su - mapred -c "/usr/hdp/current/hadoop-mapreduce-historyserver/sbin/mr-jobhistory-daemon.sh stop historyserver"

hdp-select set hadoop-mapreduce-historyserver 2.2.0.0-2041

su - mapred -c "/usr/hdp/current/hadoop-mapreduce-historyserver/sbin/mr-jobhistory-daemon.sh start historyserver"

To validate the downgrade, check that the JobHistoryServer is running. The default port is 19888. Make sure BuildVersion (listed in Application -> About) matches the previous version:

http://<host>:<port>/jobhistory

Continue with the next downgrade step.