Running an old rails 2.3.8 with rvm

I was helping set up a local (legacy) rails 2.3.8 server on a macbook today, autonomous from the system ruby installation. This was a bit messy, as modern versions of rubygems conflict with the old rails 2.3.8 environment to the tune of:

Uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)

...when you try to start the server. Here's the recipe I came up with:

1. Install rvm.

2. # Install ruby 1.8.7 and downgrade its rubygems to 1.5.3:
   rvm install 1.8.7 && \
     rvm use 1.8.7 && \
     rvm gem install -v 1.4.2 rubygems-update && \
     rvm gem update --system 1.4.2 && \
     update_rubygems && \
     echo 'Okay.'

3. # Install all the gems you need, for instance:
   rvm gem install -v 2.3.8 rails && \
     rvm gem install -v 3.0 haml && \
     rvm gem install -v 2.1 authlogic && \
     rvm gem install -v 1.0 dalli && \
     rvm gem install -v 0.2 omniauth && \
     rvm gem install -v 2.7.0 erubis && \
     rvm gem install -v 1.3.3 sqlite3 && \
     echo 'Gems installed!'

4. If needed, run rake db:setup in your rails tree to set up its databases.
5. Done! rails/script/server -p your_port is ready for action.