title: Does Rails need to be installed as a system gem?
body: <p>In every setup describing a configuring an environment with rbenv and Bundler, the instructions are always to install bundle as a system gem, using <code>gem install bundler</code>. Often, they'll also recommend <a href="https://github.com/carsomyr/rbenv-bundler" rel="nofollow noreferrer">rbenv-bundler rbenv plugin</a>, but <a href="https://github.com/rbenv/rbenv/wiki/Plugins" rel="nofollow noreferrer">the maintainers of rbenv discourage this</a>.</p>
  
  <p>What's not described is how to install Rails. Initializing a new Rails project creates a basic Gemfile for bundler. However, in order to initialize a Rails project, one needs to have Rails installed. It seems weird and even wrong to make a directory, write a basic Gemfile that includes Rails, run <code>bundle install</code>, and then initialize Rails to the current directory. In fact, I doubt that would even work well, if it worked at all.</p>
  
  <p>So, does Rails need to be installed as a system gem with <code>gem install rails</code>? If so, how does one manage multiple versions of Rails, particularly with rbenv?</p>