How to Downgrade from Ruby 1.9.2 to Ruby 1.8.7 to run Rails 2.0.2

Whole point of RVM is so that you can have multiple versions of Ruby and switch among them easily..

rvm install 1.8.7 #or some specific version - choose from the rvm list knownrvm use 1.8.7rvm gemset create rails202 #create a gemset called "rails202" for Ruby 1.8.7rvm 1.8.7@rails202 #make the gemset the current selectiongem install rails -v 2.0.2 #install rails (just for this gemset!)#now, we have a gemset called "rails202" in Ruby 1.8.7.#anytime we want to use it, we do:rvm 1.8.7@rails202#create as many gemsets needed, eg for rails 3.0.3 on Ruby 1.8.7 we can do the#similar as above. Then to use the new gemset just do:rvm 1.8.7@rails303#et voila! we are now using Rails 3.0.3 on Ruby 1.8.7 !

Use RVM and save yourself weeks of pain.

You can use multiple Ruby versions and each version has it's own separate set of gems. That way you can have 1.8.7 and 1.9.2 installed simultaneously with Rails 2 and Rails 3 gems on the former and the latter respectively.

Installing a Ruby version is as simple as typing rvm install 1.9.2 or rvm install 1.8.7. To switch between the two: rvm 1.9.2 or rvm 1.8.7.

You can set the default Ruby with rvm --default 1.9.2 or rvm --default 1.8.7.

RVM won't touch your local Ruby nor it's gems. You can switch back to it at any time: rvm system.

source ~/.rvm/scripts/rvm

rvm reload ( Reload the latest rvm installed )

rvm install 1.8.7

rvm use 1.8.7 --default