Today I upgraded to Rails 1.2.6 as I prepare to move towards Rails 2.0. Notes on this release can be found here.

Here are the steps I took.

1. Upgrade Ruby Gems to the latest version (in this case 1.0.1).
   gem update --system
2. Upgrade Ruby on Rails to the latest version (in this case 2.0.2).
   gem install rails
   To specify upgrading to Ruby on Rails 1.2.6 do this.
   gem install rails -v 1.2.6
   (What I probably should have done was a gem update because now I have installed 1.2.6 and 1.2.3.)
3. Update configuration.
   set RAILS_GEM_VERSION to ‘1.2.6’ in config/environment.rb
   rake rails:update:configs