How to install Ruby 2.1.4 on Ubuntu 14.04

Question

There is a PPA with up-to-date versions of Ruby 2.x for Ubuntu 12.04+:

$ sudo apt-add-repository ppa:brightbox/ruby-ng
$ sudo apt-get update
$ sudo apt-get install ruby2.4

$ ruby -v
ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux-gnu]

First of all, install the prerequisite libraries:

sudo apt-get update
sudo apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev

Then install rbenv, which is used to install Ruby:

cd
git clone https://github.com/rbenv/rbenv.git ~/.rbenv
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
exec $SHELL

git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
echo 'export PATH="$HOME/.rbenv/plugins/ruby-build/bin:$PATH"' >> ~/.bashrc
exec $SHELL

rbenv install 2.3.1
rbenv global 2.3.1
ruby -v

Then (optional) tell Rubygems to not install local documentation:

echo "gem: --no-ri --no-rdoc" > ~/.gemrc

Credits: https://gorails.com/setup/ubuntu/14.10

Warning!!! There are issues with Gnome-Shell. See comment below.

Best is to install it using rvm(ruby version manager).
Run following commands in a terminal:

sudo apt-get update
sudo apt-get install build-essential make curl
\curl -L https://get.rvm.io | bash -s stable
source ~/.bash_profile
rvm install ruby-2.1.4

Then check ruby versions installed and in use:

rvm list
rvm use --default ruby-2.1.4

Also you can directly add ruby bin path to PATH variable. Ruby is installed in

$HOME/.rvm/rubies export PATH=$PATH:$HOME/.rvm/rubies/ruby-2.1.4/bin

Use RVM (Ruby Version Manager) to install and manage any versions of Ruby. You can have multiple versions of Ruby installed on the machine and you can easily select the one you want.

To install RVM type into terminal:

\curl -sSL https://get.rvm.io | bash -s stable

And let it work. After that you will have RVM along with Ruby installed.

Source: RVM Site

update ubuntu:

 sudo apt-get update
 sudo apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev

Install rvm, which manages the ruby versions:

to install rvm use the following command.

 \curl -sSL https://get.rvm.io | bash -s stable
 source ~/.bash_profile
 rvm install ruby-2.1.4

Check ruby versions installed and in use:

rvm list
rvm use --default ruby-2.1.4