First: rvm implode
At least on my system I saw a bunch of permission errors while this was running. Solve this by manually destroying .rvm after rvm implode finishes.
Second: clean up left overs
sudo rm -rf ~/.rvm sudo rm -rf ~/.rvmrc sudo rm -rf /etc/rvmrc
Third: remove gems
I wanted to make sure I didn't have anything kicking around from the old version so I removed all the gems.
sudo gem list | cut -d" " -f1 | xargs sudo gem uninstall -aIx
For older gem versions you might need to loose the lx options and run more than once
sudo gem list | cut -d" " -f1 | xargs sudo gem uninstall -a
Fourth: install RBENV
On my system ~/.profile is my bash profile. This might be different on your system. Do a ls -la and look for .profile, .bashprofile, .bashrc - something like that.
cd git clone git://github.com/sstephenson/rbenv.git .rbenv
Then add this to the bottom of your ~/.profile
export PATH="$HOME/.rbenv/bin:$PATH" eval "$(rbenv init -)"
Quit and restart terminal
Fifth: install ruby-build and add you rubies
git clone git://github.com/sstephenson/ruby-build.git cd ruby-build ./install.sh
Install a ruby version and set it to be the default
rbenv install 1.9.3-p0 rbenv local 1.9.3-p0 rbenv rehash
Now's a good time to also update your ruby-gem to the latest
sudo gem update --system
Check to make sure you're actually using rbenv
> which ruby /Users/wiseleyb/.rbenv/shims/ruby > which irb /Users/wiseleyb/.rbenv/shims/irb > which rails /Users/wiseleyb/.rbenv/shims/rails
If things aren't pointing where you expect try removing the /usr/bin/whatever that's misbehaving. Reinstalling. Restarting terminal. Rechecking. This at least worked for problems I had with rails. Which I solved by:
sudo rm /usr/bin/rails sudo gem install rails