There’s a considerable lack of information about rack apps deployment other than Ruby on Rails, so I made this small tutorial for deploying Sinatra apps to CentOS 7 servers.

I’ll use a Digital Ocean droplet as an example but should work anywhere else. These are some of the technologies we’ll use:

  • CentOS 7 (Operative System)
  • Nginx (Front Facing Web Server)
  • Unicorn (App Server)
  • Ruby 2.2.2 (Programming Language)
  • Sinatra (DSL for Rack apps)

Server Configuration

This is a very basic server configuration, there are multiple steps to secure our server but we won’t talk about this on this post.

Log In

Conect to your server, log as the root user using the following command (substitute the highlighted word with your server’s public IP address):


Complete the login process by accepting the warning about host authenticity if it appears, then providing your root authentication (password or private key).

Create user

This example creates a new user called “pggalaviz”, but you should replace it with a user name that you like:

adduser pggalaviz

Next, assign a password to the new user (again, substitute “pggalaviz” with the user that you just created):

passwd pggalaviz

Enter a strong password, and repeat it again to verify it. We have a new user account with regular account privileges. However, we need to do administrative tasks. As root, run this command to add your new user to the wheel group (substitute the highlighted word with your new user):

gpasswd -a pggalaviz wheel

Now your user can run commands with super user privileges!

Public Key Authentication

If you don’t have a public key already, generate one by running this command at the terminal of your local machine (your computer not the server)!


Press ‘return key’ to accept (don’t modify the path) and add a password to your keys (this last step is optional). If you already had or you just created your keys run this command on your local machine to print your public key (

cat ~/.ssh/

it should print something like this:

ssh-rsa AAAAB3N.......zaC1yc2 localuser@machine.local

Select it all and copy it to the clipboard. On the server as the root user enter this command to switch to the user we created at the begining of this tutorial:

su - pggalaviz

Now we’re going to create a folder named .ssh and change its permissions for security reasons:

mkdir .ssh
chmod 700 .ssh

Create a new file by running:

vi .ssh/authorized_keys

Enter ‘insert’ mode by pressing i and paste your previoulsy copied ssh key. press ESC and :x to save changes.

Change the file permissions:

chmod 600 .ssh/authorized_keys

and return to the root user by running:


Now, you’ll be able to login to your server by running something like

ssh pggalaviz@SERVER_IP_ADDRESS

Restrict Root Login

Log in to your server using your user (not root) and open the SSH configuration file by running:

vi /etc/ssh/sshd_config

Probably you’ll need to add sudo before the command.

Look for a line that looks like: #PermitRootLogin yes.

Enter insert mode by pressing i and edit the line so it looks like PermitRootLogin no

Disabling remote root login is highly recommended on every server!

Press :x and enter to save changes and then run the following command to reload SSH.

sudo systemctl reload sshd.service

Install Dependencies

Install EPEL and update

First install the EPEL package:

sudo yum install epel-release

Then you should confirm that all packages are updated by running:

sudo yum update

Install Packages

Install all the packages needed such as gcc, make, git, binutils, etc.

sudo yum install -y git-core zlib zlib-devel gcc-c++ patch readline readline-devel libyaml-devel libffi-devel openssl-devel make bzip2 autoconf automake libtool bison curl sqlite-devel curl-devel

Setting Up a Ruby Environment

We’ll use ‘rbenv’ to install and manage Ruby versions, just run these commands:

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

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

you can check installation by running rbenv.

If nothing appears then logout from the server, log in again using ssh and run rbenv, everything should work now.

Now we’ll install Ruby:

rbenv install -v 2.2.2

This will install Ruby version 2.2.2, this can take some minutes. After install let’s set the default version our shell will use by running:

rbenv global 2.2.2

Finally let’s verify ruby was installed properly with this command:

ruby -v

After ruby is installed run this command to install gems without documentation and save yourself some time and disk usage:

echo "gem: --no-document" > ~/.gemrc

Now lets install some basic gems:

gem install bundler rack sinatra unicorn

Whenever you install a new version of Ruby or a gem that provides commands, you should run the rehash sub-command. This will install shims for all Ruby executables known to rbenv, which will allow you to use the executables:

rbenv rehash

Create a simple Sinatra App

Just for this tutorial lets create a simple sinatra app.

mkdir sample_app
cd sample_app

We’ll use Sinatra’s modular style, start by creating the following archives and folders inside our sample_app folder:

  |_ css
  |_ js
  |_ layouts
  |_ home.erb

Inside our Gemfile lets add:

#=> Gemfile

source ""

gem 'sinatra'
gem 'sass'
gem 'unicorn'

Inside the app.rb file lets add:

#=> app.rb
ENV['RACK_ENV'] ||= 'development'
$: << File.expand_path('../', __FILE__)

require 'sinatra/base'
require 'sass'

module SampleApp
  class App < Sinatra::Base

    set :root, File.dirname(__FILE__)
    configure do
      enable :sessions

    #Assets Routes

    get '/css/*.css' do
      content_type 'text/css', :charset => 'utf-8'
      filename = params[:splat].first
      scss filename.to_sym, :views => "#{settings.root}/assets/css", :style => :compressed

    #Main Routes

    get '/' do
      erb :home


Inside the lets add:


require 'rubygems'
require 'bundler'

Bundler.require :default, ENV['RACK_ENV'].to_sym

require File.expand_path '../app.rb', __FILE__

run SampleApp::App

Inside the views/home.erb lets add:

    <meta charset="UTF-8">
    <title>Sample App</title>
    <link rel="stylesheet" type="text/css" href="/css/app.css">

    <h1>Pedro G. Galaviz</h1>
    <p>If you can see me, it's working!</p>

Finally on app’s directory run:

bundle install

Configure Unicorn

Now we need to configure Unicorn to serve our app.

cd sample_app
vi unicorn.rb

And copy this inside the file:

root = "/home/pggalaviz/sample_app"
worker_processes 2
working_directory root
timeout 30
pid "#{root}/tmp/pids/"

stderr_path "#{root}/log/unicorn.log"
stdout_path "#{root}/log/unicorn.log"

listen "#{root}/tmp/sockets/sample_app.sock"

Create Unicorn Init Script

Now we’ll create an init script so we can manage our unicorn server.

sudo vi /etc/init.d/unicorn_sample_app

And inside this file we’ll add:


# Provides:          unicorn
# Required-Start:    $all
# Required-Stop:     $all
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts the unicorn app server
# Description:       starts unicorn using start-stop-daemon

set -e

USAGE="Usage: $0 "

# app settings

# environment settings
CMD="cd $APP_ROOT && bundle exec unicorn -c unicorn.rb -E $ENV -D"

# make sure the app exists
cd $APP_ROOT || exit 1

sig () {
  test -s "$PID" && kill -$1 `cat $PID`

oldsig () {
  test -s $OLD_PID && kill -$1 `cat $OLD_PID`

case $1 in
    sig 0 && echo >&2 "Already running" && exit 0
    echo "Starting $APP_NAME"
    su - $USER -c "$CMD"
    echo "Stopping $APP_NAME"
    sig QUIT && exit 0
    echo >&2 "Not running"
    echo "Force stopping $APP_NAME"
    sig TERM && exit 0
    echo >&2 "Not running"
    sig USR2 && echo "reloaded $APP_NAME" && exit 0
    echo >&2 "Couldn't reload, starting '$CMD' instead"
    sig USR1 && echo rotated logs OK && exit 0
    echo >&2 "Couldn't rotate logs" && exit 1
    echo >&2 $USAGE
    exit 1

Check that you change # app settings to your app and user data.

Save and exit the file. Now to enable unicorn to start on boot lets run:

sudo chmod 755 /etc/init.d/unicorn_sample_app
sudo chkconfig --levels 235 unicorn_sample_app on

Lets start our Unicorn server now:

sudo service unicorn_sample_app start

Configure Nginx

Install Nginx

First we need to install Nginx to our server. Just run:

sudo yum install nginx

next, we’ll enable it to start on server boot:

sudo chkconfig --levels 235 nginx on


First we’ll open the nginx configuration file by running:

sudo vi /etc/nginx/nginx.conf

Then change its content to look like the one below.

user  pggalaviz;
worker_processes  auto;

error_log  /var/log/nginx/error.log;
pid        /run/;
events {
    worker_connections  1024;

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;
    sendfile        on;
    keepalive_timeout  65;
    gzip  on;
    index   index.html index.htm;

    include /etc/nginx/conf.d/*.conf;

Check you changed the user to yours. Now let’s create our server file:

sudo vi /etc/nginx/conf.d/sample_app.conf

and lets add this content:

upstream sample_app_x {
  server unix:/home/pggalaviz/sample_app/tmp/sockets/sample_app.sock fail_timeout=0;

server {
    listen 80;
    server_name localhost;

    root /home/pggalaviz/sample_app/public;

    try_files $uri/index.html $uri @app;

    location @app {
        proxy_pass http://sample_app_x;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;

    error_page 500 502 503 504 /500.html;
    client_max_body_size 4G;
    keepalive_timeout 10;

Change to match your user and app’s data. Save and exit. Now let’s start our nginx server by running:

sudo service nginx start

If everything worked fine you should be able to visit your server IP address or your domain (if you already pointed it to the server) and see our home page.

By following this steps you can deploy any number of apps in the same server, just limited by your server’s resources.

Updating & Adding apps

Let’s assume you’re using GIT as your version control system and your Sinatra app code is living there (Any app).

You can log in to your server and clone the git repo to the folder where your apps will live.

For each app you’ll need to create a “unicorn.rb” file inside the app’s folder then a “Unicorn init script” and an “Nginx configuration file” on the server as we previously did.

you can start any unicorn process by typing:

sudo service unicorn_sample_app start

If you are updating your app first pull the repo code from git to your app’s folder and then type:

sudo service unicorn_sample_app restart
sudo service nginx restart

And your app should be updated accordingly.