If you’re still new to Ubuntu I’ve a post with some useful commands that’ll help you navigate and use the terminal!
Useful Unix Commands for macOS or Linux
Update and install some dependencies
apt-get is a package manager command line tool similar to Homebrew on macOS and is used to manage applications on Ubuntu. Lets update the cached packages to make sure the latest versions are available. Run the following command from the terminal.
sudo apt-get update
Now that apt-get is updated we’ll need to install some libraries that Rbenv and Ruby require. The following command will install the list of libraries that are needed. Run it in the terminal as well.
sudo apt-get install autoconf bison build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm3 libgdbm-dev

When the libraries have finished installing we can move to the next step.
Installing Git
Git didn’t come installed on this version of Ubuntu. Git is a version control system. We can use it to get applications that aren’t available through apt-get. Use apt-get to install git using the command below.
sudo apt-get install git
When git is installed we’ll be able to use the git clone command to download repositories from github.
Installing Rbenv
We can use git to clone the Rbenv code from its repository on github and put it in the hidden .rbenv directory. The following command will do just that! run it in the terminal.
git clone https://github.com/rbenv/rbenv.git ~/.rbenv

Now that we have Rbenv downloaded we’ll need to run a few commands to add Rbenv to the $PATH so we’ll have access to the rbenv command on the terminal and also Rbenv will be loaded automatically. The following commands will add to the bashrc file. Bashrc is a shell script that bash runs when its started. Bash is basically the command line in the terminal. Run these on the terminal.
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc echo 'eval "$(rbenv init -)"' >> ~/.bashrc source ~/.bashrc

Now we can check if everything has been setup correctly. We can use the type command to check for rbenv. Run the following from the terminal.
type rbenv

If you don’t see the above then maybe you have missed one of the previous steps. Check over them and try again.
To be able to install versions of Ruby with Rbenv we’ll need to install the Rbenv ruby-build plugin. This will be cloned from Github too. The following command will clone ruby-build into the Rbenv plugins directory.
git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
This will give Rbenv the install command and we can use that to install a version of Ruby.
Installing Ruby
If you have everything setup correctly we can then move onto installing Ruby. First we’ll list the versions of Ruby that are available to install. Run the following command in terminal.
rbenv install -l

Im going to install the latest stable version of Ruby which is 2.4.1 and make it the global version of Ruby. You can install and version you wish just change 2.4.1 to your desired version. Run the following commands. The install could take some time.
rbenv install 2.4.1 rbenv global 2.4.1

When the installation is finished. You can check that the installed version of Ruby is available by running the following command.
ruby -v
Install Bundler
We’ll need to install bundler to manage our gems for Rails applications.
gem install bundler
Installing Rails
Now lets install the latest version of Rails. Similar to the previous step run
gem install rails
This installs the latest version of Rails, 5.1.1 at time of writing. It could take a few minutes.

Whenever you install a version of Ruby or a gem that provides commands you will need to rehash Rbenv. Run
rbenv rehash
You can then check the version of Rails installed by running
rails -v
It should be 5.1.1
Installing A JavaScript Runtime
Some Rails features such as the Asset Pipeline require a Javascript Runtime to be installed. We’re going to install NodeJS for this. Before we can download the package we’ll need to install curl. Curl is used for transferring data. We can install it using apt-get by running
sudo apt-get install curl

With curl installed we can use it to download the latest version of NodeJS 6 and install it using apt-get
curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash - sudo apt-get install -y nodejs
Using SQLite
If you want to use the standard SQLite database that is the default lightweight database for a new Rails app you will need to install an additional library, libsqlite3-dev. Use apt-get to install it using the following command.
sudo apt-get install libsqlite3-dev
Without this library an error will occur when bundle is installing the gems for a new Rails application that uses SQLite.
Finally Create a Rails app
Everything should now be set up and ready to go. Create a Rails app to test it all out. Navigate to the directory you want to create the app and run
rails new testapp
You should see all the normal output and gems installing. You should now be ready to go with developing Rails apps on Ubuntu 16.04. This was all done on a Virtual copy of Ubuntu 16.04 running on Virtual Box.
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