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

Is there any way, on Ubuntu 9.04, to install Ruby 1.8 as ruby1.8 (or get rid of it altogether) and have Ruby 1.9 be the default ruby?

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.)