Rails 2 to 4 UpGradation (Initial Level Settings)

Steps to upgrade the rails from 2 to 4 (Initial Level Settings)

• Use latest ruby version first which is compatible with rails 4
• Upgrade your Gems
• Change versions for Gems into Gemfile .
• Find alternative for gems which have been deprecated.
• Comment some below gems if you have into you Gemfile
• gem "mongrel"
• gem "cgi_multipart_eof_fix" 
• gem "fastercsv", '1.5.0'
• gem “debugger"
• Remove versions for these two basic Gems
• gem 'mysql2'
• gem 'rake'
• Comment all the mime initializers in file config/initializers/mime_types.rb
• Add config.egger_load in all rails environments in files config/environments/*
• config.eager_load = true
• Change match keyword from file routes.rb to get

You will able to run rails server from console