Install Rails 4.0 with Ruby 2.0

Get the stable version of rvm:

$ rvm get stable

Install Ruby 2.0

$ rvm install ruby-2.0.0

Create a Gemset;

$ rvm gemset create rails-4.0

Goto that gemset:

$ rvm use ruby-2.0.0-p247@rails-4.0

Install Rails 4.0

$ gem install rails --version=4.0

Create an rvmrc file in root folder:

$ vim rvmrc
$ rvm --rvmrc use ruby-2.0.0-p247@rails-4.0

uncomment the line gem ‘therubyracer’, platforms: :ruby from Gemfile

Start the server:

$ rails s

You are ready to go!!

Changes that you may need to perform while working with Rails 4 compared to old versions:

1. Check here for the New changes in Rails 4
2. If you are using devise gem use devise version 3 or above (

rake assets:precompile – database configuration does not specify adapter

Even if we are specified the database configuration for adapter in our database.yml, sometimes we are getting the error “database configuration does not specify adapter”. Usually you are doing the command for development

$ rake assets:precompile -t

And in your database.yml, configuration for development is specified. But if you are doing

$ rake assets:precompile -t RAILS_ENV=development

then you can see the error goes.
Another way is check your database.yml for production database configuration is there or not. If you adds the production database configuration then also it works! Because while doing the precompile for assets without specifying the environment then it checks all environments db configuration.

Another way is add the following in your application.rb file

config.assets.initialize_on_precompile = false

then also it works.