Ubuntu provides a package manager system for installing system software. You’ll
use this to prepare your computer before installing Ruby. However, don’t use
apt-get to install Ruby. The package manager will install an outdated version
of Ruby. And it will install Ruby at the system level (for all users). It’s
better to use RVM to install Ruby within your user environment.
But if you have an older version of Ruby installed on your computer, there’s no need to remove it. RVM will leave your “system Ruby” untouched and use your shell to intercept any calls to Ruby. Any older Ruby versions will remain on your system and the RVM version will take precedence.
Installing RVM & Ruby
Use RVM, the Ruby Version Manager, to install Ruby and manage your Rails versions as you might need an easy way to switch between Ruby versions. Just as important, you’ll have a dependency mess if you install gems into the system environment. RVM is popular, well-supported, and full-featured.
Here’s the simplest way:
$ curl -L https://get.rvm.io | bash -s stable --ruby
The “—ruby” flag will install the newest version of Ruby. RVM includes an “autolibs” option to identify and install system software needed for your operating system. If you already have RVM installed, update it to the latest version and install Ruby:
$ rvm get stable --autolibs=enable
$ rvm install ruby
$ rvm --default use ruby-2.1.2
To list available Ruby versions, run:
$ rvm list known
For example to change to Ruby version 2.0.0-p481, run:
$ rvm install ruby-2.0.0-p481
Gems & RubyGems
RubyGems is the gem manager in Ruby. Use gem update --system to upgrade
the Ruby gem manager if necessary.
By default, when you install gems, documentation files will be installed. Developers seldom use gem documentation files (they’ll browse the web instead). Installing gem documentation files takes time, so many developers like to toggle the default so no documentation is installed. Here’s how to speed up gem installation by disabling the documentation step:
$ echo "gem: --no-document" >> ~/.gemrc
This adds the line gem: --no-document to the hidden .gemrc file in your home
directory.
Installing Rails
You can install Rails directly into the global gemset. However, many developers prefer to keep the global gemset sparse and install Rails into project-specific gemsets, so each project has the appropriate version of Rails.
If you install Rails at this point, you will install it into the global gemset. Instead, make a gemset just for the current stable release:
$ rvm use ruby-2.0.0-p481@rails4.1 --create
Install most recent stable release:
$ gem install rails
$ rails -v