chruby-and-ruby-install

sudo -s

# ruby-install
git clone https://github.com/postmodern/ruby-install
cd ruby-install && make install
ruby-install ruby -- --disable-install-doc

# environment
R=$(basename `echo /opt/rubies/ruby-*`)
echo PATH=/opt/rubies/$R/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games >> /etc/environment
GEM_ROOT=/opt/rubies/$R/lib/ruby/gems/2.0.0 >> /etc/environment

# ALSO CHECK:
# /etc/profile (for login shell)
# /etc/zshenv for all zsh instances

# chruby
git clone https://github.com/postmodern/chruby
cd chruby && make install
echo '[ -n "$BASH_VERSION" ] || [ -n "$ZSH_VERSION" ] || return
source /usr/local/share/chruby/chruby.sh
source /usr/local/share/chruby/auto.sh' > /etc/profile.d/chruby.sh