Is it possible to create a cluster on EON mode from the command line?
You can install Eon mode using admintools. The directions for on-prem storage describe how: https://www.vertica.com/docs/9.3.x/HTML/Content/Authoring/InstallationGuide/EonOnPrem/InstallingEonModeOnPremise.htm
This will work on AWS as well.
Sure! Via admintools...
In particular, the "Usage: create_db [options]" section.