After upgrading to Rails 3, getting errors in Rails 2 app

Hey all

After upgrading to Rails 3, when I try to run Rails 2 app, I get this:

Missing the Rails 2.3.8 gem. Please `gem install -v=2.3.8 rails`, update
your RAILS_GEM_VERSION setting in config/environment.rb for the Rails
version you do have installed, or comment out RAILS_GEM_VERSION to use
the latest version installed.
MacBook-Pro:MK JANUARY jmerlino$ rails -v
Rails 3.0.3

So I assume there's going to be several issues like this.

According to the railscasts, he says use the rails_upgrade plugin to
address these issues.

Anyone agrees with this?

Thanks for response.

I think that if you want to run rails 2 and 3 apps on the same machine
the best way is to use rvm, which then allows completely independent
gem sets for each app.