How to easily use Rails 3 now

Update 10th February 2010:

The instructions below were useful earlier in the development cycle. Now the beta gem has been released, the process is much easier:

gem uninstall bundler
gem install tzinfo builder memcache-client rack rack-test rack-mount
gem install erubis mail text-format thor bundler i18n
gem install rails --pre

Now that rails 3 is getting closer to release, I wanted to start playing around with it. I’ve seen a few articles on getting it up and running, but they all seemed a little bit complicated. To use rails 2.3.5 before its release, I just built the gems myself and installed them. It turns out you can easily do the same with rails 3.

First, install rails main dependencies:

gem install rake rack bundler
gem install arel --version 0.2.pre

Next, get the latest rails code from github, and install the rails gems. There may be a few errors you can safely ignore:

git clone git://
cd rails
rake install

And bang, you can start your first rails 3 project:

rails ~/apps/playground/rails3

Your existing projects shouldn’t be affected as rails is installed as a prerelease gem, but to be safe I’d recommend a tool like rvm to switch to a clean set of gems.