rbenv single & system-wide installation for Debian (tested with Debian 7.1) & Ubuntu (tested with Ubuntu 12.04 LTS)

rbenv-install-system-wide.sh

# Update, upgrade and install development tools:
apt-get update
apt-get -y upgrade
apt-get -y install build-essential
apt-get -y install git-core

# Install rbenv
git clone https://github.com/sstephenson/rbenv.git /usr/local/rbenv

# Add rbenv to the path:
echo '# rbenv setup' > /etc/profile.d/rbenv.sh
echo 'export RBENV_ROOT=/usr/local/rbenv' >> /etc/profile.d/rbenv.sh
echo 'export PATH="$RBENV_ROOT/bin:$PATH"' >> /etc/profile.d/rbenv.sh
echo 'eval "$(rbenv init -)"' >> /etc/profile.d/rbenv.sh

chmod +x /etc/profile.d/rbenv.sh
source /etc/profile.d/rbenv.sh

# Install ruby-build:
pushd /tmp
  git clone https://github.com/sstephenson/ruby-build.git
  cd ruby-build
  ./install.sh
popd

# Comments
echo "To install Ruby 2.0.0-p195 run:"
echo "sudo -i rbenv install 2.0.0-p195"

echo "To make Ruby 2.0.0-p195 the global default ruby run:"
echo "sudo -i rbenv global 2.0.0-p195"

echo "For rehashing run:"
echo "sudo -i rbenv rehash"

rbenv-install.sh

# Update, upgrade and install development tools:
apt-get update
apt-get -y upgrade
apt-get -y install build-essential
apt-get -y install git-core

# Install rbenv:
git clone https://github.com/sstephenson/rbenv.git ~/.rbenv

# Add rbenv to the path:
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.profile
echo 'eval "$(rbenv init -)"' >> ~/.profile
source ~/.profile

# Install ruby-build:
pushd /tmp
  git clone https://github.com/sstephenson/ruby-build.git
  cd ruby-build
  ./install.sh
popd

# Comments
echo "To install Ruby 2.0.0-p195 run:"
echo "rbenv install 2.0.0-p195"

echo "To make Ruby 2.0.0-p195 the global default ruby run:"
echo "rbenv global 2.0.0-p195"

echo "For rehashing run:"
echo "rbenv rehash"

Thanks!