Install via apt-get
sudo apt-get update && sudo apt-get install zsh
Getting zsh to work in ubuntu is weird, since sh does not understand the source command. So, you do this to install zsh
wget –no-check-certificate https://github.com/robbyrussell/oh-my-zsh/raw/master/tools/install.sh -O – | sh
and then you change your shell to zsh
chsh -s `which zsh`
and then restart
sudo shutdown -r 0
Make sure your rvm is loaded in your .zshrc
[[ -s "$HOME/.rvm/scripts/rvm" ]] && . “$HOME/.rvm/scripts/rvm”
This problem is explained in depth in this issue