Intro:

Most of the Rails application deployed are with nginx and unicorn configuration, So sharing nginx and unicorn configuration we will need to make the rails application serve at HTTP port 80.

Here im not going to create rails app or configure any VPS server,We can get all the details like capistrano, setting up the server details from this post. So we are going to have just nginx configuration and unicorn configuration here.

From previous post we will have to add unicorn to your Gemfile, bundle it and deploy.

gem 'unicorn'

Now we will have a unicorn configuration inside the app/config/unicorn.rb

root = "/home/ubuntu/apps/app_name/current"
working_directory root
pid "#{root}/tmp/pids/unicorn.pid"
stderr_path "#{root}/log/unicorn.log"
stdout_path "#{root}/log/unicorn.log"

listen "/tmp/unicorn.app_name.sock"
worker_processes 10
timeout 30

preload_app true

before_fork do |server, worker|
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.connection.disconnect!
  end
  old_pid = "/tmp/unicorn.my_site.pid.oldbin"
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill("QUIT", File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
    end
  end
end

after_fork do |server, worker|
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.establish_connection
  end
end

To start the rails app we will need to create the init file and place it in /etc/init.d/appname

#!/bin/sh
### BEGIN INIT INFO
# Provides:          unicorn
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Manage unicorn server
# Description:       Start, stop, restart unicorn server for a specific application.
### END INIT INFO
set -e

# Feel free to change any of the following variables for your app:
TIMEOUT=${TIMEOUT-60}
APP_ROOT=/home/ubuntu/apps/app_name/current
PID=$APP_ROOT/tmp/pids/unicorn.pid
CMD="cd $APP_ROOT; bundle exec unicorn -D -c $APP_ROOT/config/unicorn.rb -E production"
AS_USER=ubuntu
set -u

OLD_PIN="$PID.oldbin"

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

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

run () {
  if [ "$(id -un)" = "$AS_USER" ]; then
    eval $1
  else
    su -c "$1" - $AS_USER
  fi
}

case "$1" in
start)
  sig 0 && echo >&2 "Already running" && exit 0
  run "$CMD"
  ;;
stop)
  sig QUIT && exit 0
  echo >&2 "Not running"
  ;;
force-stop)
  sig TERM && exit 0
  echo >&2 "Not running"
  ;;
restart|reload)
  sig USR2 && echo reloaded OK && exit 0
  echo >&2 "Couldn't reload, starting '$CMD' instead"
  run "$CMD"
  ;;
upgrade)
  if sig USR2 && sleep 2 && sig 0 && oldsig QUIT
  then
    n=$TIMEOUT
    while test -s $OLD_PIN && test $n -ge 0
    do
      printf '.' && sleep 1 && n=$(( $n - 1 ))
    done
    echo

    if test $n -lt 0 && test -s $OLD_PIN
    then
      echo >&2 "$OLD_PIN still exists after $TIMEOUT seconds"
      exit 1
    fi
    exit 0
  fi
  echo >&2 "Couldn't upgrade, starting '$CMD' instead"
  run "$CMD"
  ;;
reopen-logs)
  sig USR1
  ;;
*)
  echo >&2 "Usage: $0 <start|stop|restart|upgrade|force-stop|reopen-logs>"
  exit 1
  ;;
esac

Atlast we will need to configure the nginx configuration /etc/nginx/sites-available/default

upstream unicorn {
  server unix:/tmp/unicorn.app_name.sock fail_timeout=0;
}

server {
  listen 80 default deferred;
  server_name x.x.x.x;
  root /home/ubuntu/apps/app_name/current/public;

  location ^~ /assets/ {
    gzip_static on;
    expires max;
    add_header Cache-Control public;
  }

  try_files $uri/index.html $uri @unicorn;
  location @unicorn {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;
    proxy_pass http://unicorn;
  }

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

Then restart the nginx server. We can start the unicorn with /etc/init.d/app_name start

---