Whirr support the following instance roles: dn, jt, nn, tt, zk, hbase-avroserver, hbase-master, hbase-regionserver, hbase-restserver, hbase-thriftserver and as you can see the naming is inconsistent and sometimes it's hard to guess the meaning.
Tom White replied on the email list:
"The shorter names (nn, zk, etc) predate Whirr to when the roles were a part of the group name and had to be kept short to conform to various
length restrictions. We do things differently now that we have multi-cloud support, so keeping them short is less important, and indeed with a global namespace (since service name is optional) there is even more reason to make them distinctive and unique. So I would suggest the longer, hyphenated form that we adopted for HBase, like hbase-regionserver; so the pattern is <service-name>-<daemon>.
There's not much harm in keeping the shorter forms around, but we could introduce aliases like hadoop-namenode, zookeeper, etc and
deprecate the short ones."