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You can basically do this with the "building" gem: https://github.com/CenturyLinkLabs/building

It uses Heroku buildpacks to build self-contained containers with all your dependencies with one command: building containername

Dokku is great, and has a PG plugin:

https://github.com/progrium/dokku

https://github.com/Kloadut/dokku-pg-plugin

DO has a Dokku vm you can select when you spin up a new droplet.

Chef-solo is probably more up your alley. You should be able to easily find recipes for Postgres, Nginx, RVM/rbenv, etc. to automate the building of the server.

Try https://www.cloud66.com/, it does what you want, but for some money.

Cloud66 is kind of incredible, I was an early beta tester for them and they really are hitting an interesting price/value point wrt managing complex systems.