rbenv
pi
$ cd /opt/src
$ git clone https://github.com/rbenv/rbenv.git
$ sudoedit /etc/profile.d/rbenv.sh
/etc/profile.d/rbenv.sh
export RBENV_ROOT=/opt/src/rbenv
export PATH="$RBENV_ROOT/bin:$PATH"
eval "$(rbenv init -)"
pi
$ source /etc/profile.d/rbenv.sh
ruby-build
pi
$ mkdir /opt/src/rbenv/plugins
$ cd /opt/src/rbenv/plugins
$ git clone git://github.com/sstephenson/ruby-build.git
$ cd /opt/src/rbenv/plugins/ruby-build
$ sudo ./install.sh
rbenv-gemset
pi
$ cd /opt/src/rbenv/plugins
$ git clone git://github.com/jamis/rbenv-gemset.git
rbenv-binstubs
pi
$ cd /opt/src/rbenv/plugins
$ git clone https://github.com/ianheggie/rbenv-binstubs.git
Ruby
pi
$ sudo apt-get install -y libreadline-dev
$ rbenv install 2.4.0
$ rbenv rehash
$ rbenv global 2.4.0