Picking up a thread again from
MAPREDUCE-987, I've found it very useful to have a CLI driver for running a single-process DFS cluster, particularly when developing features in HDFS clients. For example, being able to spin up a local cluster easily was tremendously useful for correctness testing of HDFS-2834.
I'd like to contribute a class based on the patch for
MAPREDUCE-987 we've been using fairly extensively. Only for DFS, not MR since much has changed MR-side since the original patch.