deploy.rb

require 'bundler/capistrano'

set :application, "net"
set :repository,  "git@githost.com:net.git"

set :scm, :git

set :default_environment, {
  'PATH' => "$HOME/.rbenv/shims:$HOME/.rbenv/bin:$PATH"
}

set :use_sudo, false

default_run_options[:pty] = true

set :user, "deployer"
set :group, user
set :runner, user

set :host, "#{user}@host.com"
role :web, host
role :app, host

set :rack_env, :production

set :deploy_to, "/srv/#{application}"
set :unicorn_conf, "#{current_path}/config/unicorn.rb"
set :unicorn_pid, "#{shared_path}/pids/unicorn.pid"

set :public_children, ["css","img","js"]

namespace :deploy do

  task :restart do
    run "if [ -f #{unicorn_pid} ]; then kill -USR2 `cat #{unicorn_pid}`; else cd #{current_path} && bundle exec unicorn -c #{unicorn_conf} -E #{rack_env} -D; fi"
  end

  task :start do
    run "cd #{current_path} && bundle exec unicorn -c #{unicorn_conf} -E #{rack_env} -D"
  end

  task :stop do
    run "if [ -f #{unicorn_pid} ]; then kill -QUIT `cat #{unicorn_pid}`; fi"
  end

end

nginx.conf

upstream net_unicorn {
    server unix:/srv/net/shared/unicorn.sock fail_timeout=0;
}

server {
    server_name example.net;
    rewrite ^(.*) http://www.example.net$1 permanent;
}

server {
    server_name www.example.net;
    root /srv/net/current/public;

    location / {
        try_files $uri @net;
    }

    location @net {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_pass http://net_unicorn;
    }
}

unicorn.rb

# define paths and filenames
deploy_to = "/srv/net"
rack_root = "#{deploy_to}/current"
pid_file = "#{deploy_to}/shared/pids/unicorn.pid"
socket_file= "#{deploy_to}/shared/unicorn.sock"
log_file = "#{rack_root}/log/unicorn.log"
err_log = "#{rack_root}/log/unicorn_error.log"
old_pid = pid_file + '.oldbin'

timeout 30
worker_processes 2
listen socket_file, :backlog => 1024

pid pid_file
stderr_path err_log
stdout_path log_file

before_fork do |server, worker|
  # zero downtime deploy magic:
  # if unicorn is already running, ask it to start a new process and quit.
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill("QUIT", File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      # already done
    end
  end
end