How do I make Ruby 1.9 the default Ruby on Ubuntu?

Question

I'm not really sure, but maybe this can help:

update-alternatives --config ruby

... and here's the non-interactive, scriptable, way:

update-alternatives --set ruby /usr/bin/ruby1.9.1

You may find out about available alternatives and respective /usr/bin/... paths by doing:

update-alternatives --query ruby

Martin - Take a look at the following link: http://ryanbigg.com/2010/12/ubuntu-ruby-rvm-rails-and-you/

This is where installation of ruby is heading for ubuntu servers. This should allow you to not only switch to a ruby version when needed, but also keep gems separated based on ruby versions, etc.

You can completely remove Ruby 1.8 too with:

sudo apt-get remove libruby1.8 ruby1.8 ruby1.8-dev rubygems1.8

After that, you will only have Ruby 1.9 installed.

sudo \curl -L https://get.rvm.io | bash -s stable --ruby --rails

will install an up-to-date version of ruby (and rails), and allow you to avoid brokenness of Ubuntu's RVM, see https://stackoverflow.com/a/9056395/497756.

If you go this route, get rid of Ubuntu-installed versions and associated packages like bundle.

Details here: https://rvm.io/rvm/install/

(Note: this is the TL;DR version of the post by henry74.)