Ubuntu Installation is not properly documented in Hortonworks docs. Many docs don't even mention Ubuntu OS. Is HW trying to avoid ubuntu support?
The docs mention ubuntu explicitely, take a look at ambari installation : http://docs.hortonworks.com/HDPDocuments/Ambari-126.96.36.199/bk_ambari-installation/content/download_the_...
Even for manual install, are you talking about something else than Ambari or HDP ?
ok , you're talking about preparing the environment. That's shall be only to not overload the docs since the repositories are filled with ubuntu (same with SuSE for example), as the commands are very basic (quite replacing yum by apt)
Hortonworks is delivering Ubuntu rpm means they explicitely support it (my point of view from a field perspective a large majority of distros is centos/RH/Suse), but certainly can do better for the documentation.