In this tutorial, we will install multiple Ruby versions on Ubuntu using rbenv.

Prerequisites

You need a workstation or a virtual server installed with Ubuntu OS 20.04 or a later version to complete this tutorial.

If you only have a Mac or a Windows workstation, you can quickly run an Ubuntu virtual server on it with Multipass.

Outline

• Install rbenv
• Install ruby-build plugin
• Install the primary Ruby version
• Install additional Ruby versions
• Switch between Ruby versions
• Upgrade ruby-build plugin
• Wrapping up

Install rbenv

rbenv is a Ruby version manager.

It lets you install and switch between different Ruby versions in your development workstation or production server.

rbenv is available via package managers on several platforms. But, we can install rbenv manually from its GitHub repo.

Open a terminal and type in this command on your Ubuntu workstation to install rbenv:

$ git clone https://github.com/rbenv/rbenv.git ~/.rbenv

You can also use WSL, if you are using a Windows workstation.

Configure shell to load rbenv on startup:

$ ~/.rbenv/bin/rbenv init

Reload shell:

$ exec "$SHELL"

Install ruby-build plugin

rbenv depends on the ruby-build plugin for installing Ruby from source.

Install the ruby-buildplugin:

$ git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build

Install the primary Ruby version

List the latest available Ruby versions:

$ rbenv install -l

ruby-build installs a Ruby version by compiling from the source.

So we need to install the build dependencies.

$ sudo apt update
$ sudo apt install build-essential libssl-dev libreadline-dev zlib1g-dev autoconf bison libyaml-dev libreadline-dev libncurses5-dev libffi-dev libgdbm-dev

Install Ruby 3.3.4 which is the latest as of today:

$ rbenv install 3.3.4

This command will take several minutes to complete.

Set the installed Ruby version as the global Ruby version:

$ rbenv global 3.3.4

Install additional Ruby versions

List all known Ruby versions

$ rbenv install 3.3.3

Check the installed Ruby versions:

$ rbenv versions
  3.3.3
* 3.3.4 (set by /home/ubuntu/.rbenv/version)

Switch between Ruby versions

Now, we have two Ruby versions installed in our system.

Select Ruby version 3.3.3:

$ rbenv version 3.3.3

This will set the Ruby version to 3.3.3 for the current shell. If you log out and log in, the Ruby version will again be set to the global Ruby version.

You can set the Ruby version persistently for a working path by creating a file .ruby-version.

Create directry my-blog and switch to it:

$ mkdir my-blog && cd $_

Create the file .ruby-version to select Ruby version 3.3.0

$ echo 3.3.3 > .ruby-version

Check the Ruby version:

$ ruby -v
ruby 3.3.3 (2024-06-12 revision f1c7b6f435) [x86_64-linux]

Create subdirectory logs inside the my-blog parent directory and check the Ruby version.

$ mkdir logs && cd $_
$ ruby -v

Still, the Ruby version would be 3.3.3.

So the Ruby version set in .ruby-version is applicable to all subdirectories inside the parent directory.

You can override the Ruby version by creating .ruby-version file inside a subdirectory.

$ echo 3.3.4 > .ruby-version

Check the Ruby version now:

$ ruby -v

It will be set to 3.3.4.

Upgrade ruby-build plugin

When a new Ruby version is released, you must upgrade the ruby-build plugin before you can install the newly released Ruby version.

Upgrade ruby-build plugin:

$ git -C "$(rbenv root)"/plugins/ruby-build pull

Wrapping up

In this tutorial, we used rbenv to install and switch between multiple Ruby versions.

rbenv is a simple tool that just modifies the PATH variable to set the current Ruby version. If you want more features and functions while managing multiple Ruby versions you can use rvm.