Example Mina script for Rails app and Unicorn

deploy.rb

require 'mina/bundler'
require 'mina/rails'
require 'mina/git'
require 'mina/rbenv'

set :domain, 'your_server'
set :user, 'ubuntu'
set :deploy_to, '/path/to/app'
set :app_path, "#{deploy_to}/#{current_path}"
set :repository, 'repo'
set :branch, 'master'

set :shared_paths, ['config/database.yml', 'config/secrets.yml', 'log']

set :forward_agent, true # solving the problem to bundle private gems

task :environment do
  invoke :'rbenv:load'
  invoke :'important_variables'
end

task :important_variables => :environment do
  queue! %[source /home/ubuntu/.secret_key_base]
  queue! %[source /home/ubuntu/.mysql]
end

task :setup => :environment do
  queue! %[mkdir -p "#{deploy_to}/#{shared_path}/log"]
  queue! %[chmod g+rx,u+rwx "#{deploy_to}/#{shared_path}/log"]

  queue! %[touch "#{deploy_to}/#{shared_path}/config/database.yml"]
  queue  %[echo "-----> Be sure to edit '#{deploy_to}/#{shared_path}/config/database.yml'."]

  queue! %[touch "#{deploy_to}/#{shared_path}/config/secrets.yml"]
  queue  %[echo "-----> Be sure to edit '#{deploy_to}/#{shared_path}/config/secrets.yml'."]
end

desc "Deploys the current version to the server."
task :deploy => :environment do
  deploy do
    invoke :'git:clone'
    invoke :'deploy:link_shared_paths'
    invoke :'bundle:install'
    invoke :'rails:db_migrate'
    invoke :'deploy:cleanup'
    
    to :launch do
      queue "mkdir -p #{deploy_to}/#{current_path}/tmp/"
      queue "touch #{deploy_to}/#{current_path}/tmp/restart.txt"
    end
  end
end

# Unicorn
# ==============================================================================
namespace :unicorn do
  set :unicorn_pid, "#{app_path}/tmp/unicorn.pid"
  set :start_unicorn, %{
cd #{app_path}
bundle exec unicorn -c #{app_path}/config/unicorn.rb -E #{rails_env} -D
  }

  # Start task
  # ------------------------------------------------------------------------------
  desc "Start unicorn"
  task :start => :environment do
    queue 'echo "-----> Start Unicorn"'
    queue! start_unicorn
  end

  # Stop task
  # ------------------------------------------------------------------------------
  desc "Stop unicorn"
  task :stop => :environment do
    queue 'echo "-----> Stop Unicorn"'
    queue! %{
test -s "#{unicorn_pid}" && kill -QUIT `cat "#{unicorn_pid}"` && echo "Stop Ok" && exit 0
echo >&2 "Not running"
    }
  end

  # Restart task
  # ------------------------------------------------------------------------------
  desc "Restart unicorn using 'upgrade'"
  task :restart => :environment do
    invoke 'unicorn:stop'
    invoke 'unicorn:start'
  end
end