Does HDP2.6.5 support MR1 JAR files or do we need to modify the JARs to make to compatible with MR2? Can any one share the document that states only MR2 is supported in HDP 2.6.5
The best answer to "will it work?" is "what did your testing show?". Give it a try and let us all know. I'm guessing you just have some old legacy code you can't change? I'm also guessing it will work!
So... to be more precise, the 2.6.5 release notes component page, https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.5/bk_release-notes/content/comp_versions.html... says Hadoop 2.7.3 is being used. The Apache Hadoop page for MRv1 compatibility with MRv2, https://hadoop.apache.org/docs/r2.7.3/hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduce... suggests you are probably in good shape for previously compiled MRv1 apps from running on MRv2, but doesn't quite guarantee if you need to compile them against MRv2 you'll be so lucky.
Good luck and happy Hadooping!
This was moved into the Hadoop Core Mon May 6 15:19:22 PDT 2019; it was previously mis-posted in the Community Help track.