First list ruby versions in RVM
rvm list
For example mine says
ruby-1.9.3-p484 [ x86_64 ]
=* ruby-2.1.0 [ x86_64 ]
# => - current
# =* - current && default
# * - default
To use a ruby version use command like
rvm use ruby-2.1.0
You can set default ruby like this
rvm use --default ruby-2.1.0
Now check your ruby version
ruby -v
To ensure that non-interactive shells have access to RVM
Edit .bashrc
using this command
sudo gedit /home/$USER/.bashrc
Make sure you have these lines there. If not add it.
PATH=$PATH:$HOME/.rvm/bin # Add RVM to PATH for scripting
[[ -s "/home/`whoami`/.rvm/scripts/rvm" ]] && source "/home/`whoami`/.rvm/scripts/rvm"
Now edit your .bash_profile using this command
sudo gedit /home/$USER/.bash_profile
Make sure you have these lines there. If not add it.
if [ -f "$HOME/.bashrc" ]; then
source $HOME/.bashrc
fi
Restart your terminal.