HADOOP-8712 the start-dfs.sh script is generating malformed ssh commands when the native hadoop libraries are not present. This is because hdfs getconf is printing a warning, and that warning is accidentally interpreted as one of the machines to target for ssh.
Here's an example output of hdfs getconf:
$ hdfs getconf -namenodes 2>/dev/null
2013-01-22 21:03:59,543 WARN util.NativeCodeLoader (NativeCodeLoader.java:<clinit>(62)) - Unable to load native-hadoop library for your platform... using builtin-java classes where applicable