I found out that there are actually 3 user ids created by the Ambari installtion of HDP 1.3.3, that exceed 8 characters :
The Ambari installation process allows us to change the default user ids for zookeeper and ambari_qa. But I can’t figure out what creates the user rrdcached. It is probably by some ganglia installation process. I checked the puppet scripts for ganglia in the HDP stack, and I could not find anything about the user rrdcached, It does not even appear to be used by the rrdached daemon. When I ran the ps -ef command, I noticed that rrdached daemon is run by user “nobody”. Therefore, I am wondering if the user rrdcached and its group rrdached are needed at all. Can someone please shed some light on this?