Distcp v2 (hadoop-tools/hadoop-distcp/...) and Distcp v1 (hadoop-tools/hadoop-extras/...) are currently both built, and the resulting hadoop-distcp-x.jar and hadoop-extras-x.jar end up in the same class path directory. This causes some undeterministic problems, where v1 is launched when v2 is intended, or even v2 is launched, but may later fail on various nodes because of mismatch with v1.
http://docs.oracle.com/javase/6/docs/technotes/tools/windows/classpath.html ("Understanding class path wildcards")
"The order in which the JAR files in a directory are enumerated in the expanded class path is not specified and may vary from platform to platform and even from moment to moment on the same machine."
Suggest distcpv1 be deprecated at this point, possibly by discontinuing build of distcpv1.