HADOOP-230 cover syntax changes. Capturing here some DFS command line semantic comments between Doug and I:
The goal for DFS should be "UNIX-like when possible". The goals of HDFS are primarily to be usable, scalable, reliable, high-performance, and, secondarily, not to be gratuitously incompatible with UNIX. So, when it's easy to be compatible, we certainly should. But when UNIX compatibility fights with one of those other goals, it may lose.
Two examples of incompatibilities with UNIX (that will need to be evaluated against the above goal), are:
UNIX: cp foo bar succeeds if bar exists
DFS: dfs -put foo bar fails if bar exists. (same for dfs -cp).
UNIX: mkdir foo fails if foo exists
DFS: dfs -mkdir succeeds silently if foo exists and is a directory (if foo is a file than it fails).
Many more such incompatibilities exist.