Rails, Git, Capistrano, EC2 and SSH

I wrote a post last year on configuring SSH to communicate with an EC2 via Capistrano. Here is a followup post that shows how to deploy a Rails app from your local machine to an EC2 node.

I'm skipping the database used in the Rails app and all the application start/restart/stop details that might involve Apache and Passenger. The focus is on getting the code copied over to EC2.

Here are the prerequisites:
1: An EC2 instance with all the necessary packages and Ruby gems needed for your app to run. That's a big topic in itself - but not for this post.
2: A client machine with Rails, git, and capistrano installed (In my case this is all on a Mac OS X 10.5 system, Rails 2.2.2, etc.)
3: A SSH key pair (see my previous post) - Note that this is NOT the same as your EC2 keypair (which you need as well)

I suggest you try creating an deploying a test app like this one before you try to deploy a real app.

1: Create a new Rails app - we'll call is 'deploytest'

$ rails deploytest
$ cd deploytest

2: Create a local Git repository for it

$ git init
$ git add *
$ git commit -a -m 'initial commit'
$ git status

3: Create a couple of Capistrano files

$ capify .

4: Edit config/deploy.rb

# The name of your app
set :application, "deploytest"
# The directory on the EC2 node that will be deployed to
set :deploy_to, "/mnt/#{application}"
# The type of Source Code Management system you are using
set :scm, :git
# The location of the LOCAL repository relative to the current app
set :repository,  "."
# The way in which files will be transferred from repository to remote host
# If you were using a hosted github repository this would be slightly different
set :deploy_via, :copy

# The address of the remote host on EC2 (the Public DNS address)
set :location, "ec2-174-100-100-100.compute-1.amazonaws.com"
# setup some Capistrano roles
role :app, location
role :web, location
role :db,  location, :primary => true

# Set up SSH so it can connect to the EC2 node - assumes your SSH key is in ~/.ssh/id_rsa
set :user, "root"
ssh_options[:keys] = [File.join(ENV["HOME"], ".ssh", "id_rsa")] 

The only account on a default EC2 instance is root. You probably want to create a second user that is responsible for your application.

5: Copy your SSH public key to your EC2 node

$ scp -i ~/my-ec2-keypair ~/.ssh/id_rsa.pub root@ec2-174-100-100-100.compute-1.amazonaws.com:/root/.ssh/authorized_keys2

NOTE the filename authorized_keys2 - not authorized_keys!!

6: Setup the EC2 node for Capistrano deployment.
From your LOCAL machine, not the EC2 node:

$ cap deploy:setup

7: Finally, deploy your application

$ cap deploy

You will see lots of output and with this dummy application some of those will report errors/warnings. Don't worry about that for now.

8: Check that the Deployment was successful
Connect to the EC2 node with SSH the regular way, cd to the app directory and check that everything is there. If that is all working then you are ready to deploy a real application and add custom tasks for managing the database, restarting the server etc.

Bear in mind that Capistrano add new 'releases' of your software in separate directories and symlinks the 'current' directory to the latest. So the root of your deployed application is the 'current' subdirectory.


Good luck.