Major Description
hadoop jar --help and hadoop jar help commands show outputs like this:
WARNING: Use "yarn jar" to launch YARN applications. JAR does not exist or is not a normal file: /root/--help
Only if called with no arguments: hadoop jar we get the usage text, but even in that case we get:
WARNING: Use "yarn jar" to launch YARN applications. RunJar jarFile [mainClass] args...
Where RunJar is wrapped by the hadoop script (so it should not be displayed).
hadoop --help displays the following:
jar <jar> run a jar file. NOTE: please use "yarn jar" to launch YARN applications, not this command.
which is fine, but CommandsManual.md tells a bit more information about the usage of this command:
Usage: hadoop jar <jar> [mainClass] args...
My suggestion is to add a --help option to the hadoop jar command that would display this message.