I just walk-through with the installation of Ruby on Rails on Ubuntu using RVM.
First I have logged in as the root user.
Then I started with the f
Your surest bet is to use home brew. Funny part is if you try brew upgrade ruby, you will have an error if brew wasn't used to install ruby in the first instance so use:
$ brew install ruby
Then afterwards use
$ brew upgrade ruby
You may need to close and reopen your terminal to see the effect of the upgrade by typing
$ ruby -v