Ruby Version Manager (RVM) can be used to manage multiple versions of Ruby.
Some customers may be familiar working with RVM in their development environments, and you can run RVM on your web hosting account too.
If you require a specific version of Ruby, or you have a complex app then you may want to use RVM as well.
Login to the web server via SSH with your username, and your password.
Run the below command (without the '#')
# bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)
Once installation has finished the PATH variable is updated in your .bashrc file, to pick up the changes, please close your session and login again. Normally a 'source ~/.bashrc' command is used to pick the changes but RVM is picky about this.
Now you can install the Ruby version of your choosing, for example, Rails 1.9.3.
# rvm install 1.9.3
Now that Ruby has installed under your ~/.rvm directory, you can make it the default Ruby version
# rvm use --default 1.9.3
You should now have some base gems installed, now you can install the gems you want, by using the gem or bundle commands.
You can roll back to using the system-wide Ruby installation at any point.
# rvm use system
If you wish to remove RVM it's quite simple. everything is installed into ~/.rvm so you can remove this directory and the entry in your ~/.bashrc file
# rm -rf ~/.rvm
# nano ~/.bashrc
Remove the line at the bottom that look likes this..
PATH=$PATH:$HOME/.rvm/bin # Add RVM to PATH for scripting
Save the file
RVM Cheat Sheet - https://gist.github.com/fajrif/1024971