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usage: 
  letsencrypt [SUBCOMMAND] [options] [-d domain] [-d domain] ...

The Let's Encrypt agent can obtain and install HTTPS/TLS/SSL certificates.  By
default, it will attempt to use a webserver both for obtaining and installing
the cert. Major SUBCOMMANDS are:

  (default) run        Obtain & install a cert in your current webserver
  certonly             Obtain cert, but do not install it (aka "auth")
  install              Install a previously obtained cert in a server

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How To Install Ruby on Rails on Ubuntu 12.04 LTS (Precise Pangolin) with RVM
Tags: Ruby on Rails, Ruby Distribution: Ubuntu
About Ruby on Rails

Ruby on Rails is an application stack that provides developers with a framework to quickly create a variety of web applications. Ruby on Rails does take a little while to install on a virtual server, but luckily there are a lot of helpful tools to make this process as easy as possible. You can run this tutorial on your droplet as a user with sudo privileges. You can check out how to set that up here: Ubuntu Server Setup

Step One— Install Ruby with RVM
Before we do anything else, we should run a quick update to make sure that all of the packages we download to our VPS are up to date:

sudo apt-get update