To run this blog, I must admit that I encountered some problem to have everything working.
Because of that, I wrote for myself a simple guide to setup a deployment enviroment with Ubuntu/Debian, and I would to share it (tested on Ubuntu 12.04).

Put you code under version control

This is the first step to deploy your code. I use git, to install it (you can find it here). After installation, init your app

cd yourapp
git init
git add .
git commit -m "initial commit"

Deployment

SSH Stuff

To connect to your deployment machine I recommend to setup a custom SSH connection.
Generate a key on the development machine:

ssh-keygen

Walk through the key generator and set a password, the key file by default goes into ~/.ssh/id_rsa.

Next, you need to copy the generated key to the remote server where you want to setup password-less login with

cat ~/.ssh/id_rsa.pub | ssh user@remotehost 'cat >> ~/.ssh/authorized_keys'

And then edit the file ~/.ssh/config to have something like that:

Host host
HostName remotehost
User user
IdentityFile ~/.ssh/id_rsa

After you have restarted your shell, check if login works password-less

ssh user@remotehost

The next steps have to be executed on your deployment machine.

Install Ruby and Rails

To deploy, you have to install Ruby and then Rails. To do it, I would recommend you to use RVM (Ruby Version Manager) instead of APT, because lets you to install multiple Ruby versions and use them all together.

So, no more chatting! Install ruby + rails via RVM and then load it in all opened shells

curl -L https://get.rvm.io | bash -s stable --rails
source ~/.rvm/scripts/rvm

Install Nginx + Passenger

To make Rails works with your favorite web server, you have to install the Passenger’s gem and module.
I used nginx, but for Apache is pretty similar.

Install the gem and then install nginx with Passenger’s module

gem install passenger
rvmsudo passenger-install-nginx-module

This step could take some minutes, but if everything goes ok, copy these lines to /opt/nginx/conf/nginx.conf

passenger_root /home/user/.rvm/gems/ruby-1.9.3-p194/gems/passenger-3.0.17;
passenger_ruby /home/user/.rvm/wrappers/ruby-1.9.3-p194/ruby;

Setting the preferences of your webserver inside http { … }

server {
    listen 80;
    server_name yourapp.com;
    root /home/youruser/public_html/yourapp/current/public;
    passenger_enabled on;

    access_log /home/user/public_html/yourapp/current/log/access.log;
    error_log /home/user/public_html/yourapp/current/log/error.log;
}

Be sure to point to current/public folder!

Then, create a script to control nginx:

wget -O init-deb.sh http://library.linode.com/assets/660-init-deb.sh
sudo mv init-deb.sh /etc/init.d/nginx
sudo chmod +x /etc/init.d/nginx
sudo /usr/sbin/update-rc.d -f nginx defaults  

You can now control nginx with this script

sudo /etc/init.d/nginx stop
sudo /etc/init.d/nginx start

Install your favorite DB

I installed MySQL, not my favorite but one of the most known.

sudo apt-get install mysql-server mysql-client
sudo apt-get install libmysql-ruby libmysqlclient-dev 
gem install mysql2

(I used mysql2 gem because is better than its old daddy mysql. More info here)

Install node.js

One of the other things you’ll want is Node.js. This will help you do the compiling of assets on deployments

sudo apt-add-repository ppa:chris-lea/node.js
sudo apt-get -y update
sudo apt-get -y install nodejs`

Deploy with capistrano

To deploy, the first step is to create a remote repository in which push your code, so SSH into your deployment machine and create it.

# on remote-deployment machine
mkdir -p ~/git/yourapp.git
cd ~/git/yourapp.git
git --bare init

Then, add gem 'capistrano' to your Gemfile, install it

bundle install

and set git to push to you deployment machine

bundle pack
git add Gemfile Gemfile.lock vendor/cache
git commit -m "bundle gems"
git remote add origin host:git/yourapp.git
git push origin master

The last thing to do is to edit the file config/deploy.rb to let Capistrano to work with your deployment machine.
Set :deploy_to to your public folder in which you have your webserver’s files.

set :user, 'user'
set :domain, 'yourremotehost'
set :application, 'yourapp'

set :repository, "host:git/#{application}.git"
set :deploy_to, "/home/#{user}/public_html/#{application}" 
ssh_options[:keys] = %w(~/.ssh/id_rsa)

# miscellaneous options
set :deploy_via, :remote_cache
set :scm, 'git'
set :branch, 'master'
set :scm_verbose, true
set :use_sudo, false

Finally, init capistrano

cap deploy:setup

check if everything works

cap deploy:check

run your migrations

cap deploy:migrations

and deploy your app

git add .
git commit -m "add cap files"
git push
cap deploy

Do not hesitate to tell me “Hey, you wrote a lot of bullshit!”, because it’s possibile that I forget something.

Do not expect that everything works the first time because there is a lot of stuff, but this worked for me so I hope it works for you too.