Install Rails 4.1 on Ubuntu 14.04

# Install Rails
# Install ruby 2.1
sudo add-apt-repository ppa:brightbox/ruby-ng
sudo apt-get update
sudo apt-get install ruby2.1

# Install ruby Dev-Kit
sudo apt-get install ruby2.1-dev

# Install sqlite3
sudo apt-get install sqlite3

# Install sqlite3 Dev-Kit
sudo apt-get install libsqlite3-dev

# Install nodejs (javascript-runtime)
sudo apt-get install nodejs

# Install Rails
sudo gem install rails -v "=4.1"

# create a new rails project and run it
sudo rails new blog
cd blog
sudo rails server

# Open browser, link to http://localhost:3000/
# Done
# Then follow official Rails Guide
# http://guides.rubyonrails.org/getting_started.html

Reference:

What versions of ruby are supported in 14.04?

Failed to build gem native extension — Rails install

sqlite3-ruby install error on Ubuntu

ExecJS and could not find a JavaScript runtime