Sunzi-Rails

"The supreme art of war is to subdue the enemy without fighting." - Sunzi

Sunzi is the easiest server provisioning utility designed for mere mortals. If Chef or Puppet is driving you nuts, try Sunzi!

Sunzi assumes that modern Linux distributions have (mostly) sane defaults and great package managers.

Its design goals are:

• It's just shell script. No clunky Ruby DSL involved. Most of the information about server configuration on the web is written in shell commands. Just copy-paste them, rather than translate it into an arbitrary DSL. Also, Bash is the greatest common denominator on minimum Linux installs.
• Focus on diff from default. No big-bang overwriting. Append or replace the smallest possible piece of data in a config file. Loads of custom configurations make it difficult to understand what you are really doing.
• Always use the root user. Think twice before blindly assuming you need a regular user - it doesn't add any security benefit for server provisioning, it just adds extra verbosity for nothing. However, it doesn't mean that you shouldn't create regular users with Sunzi - feel free to write your own recipes.
• Minimum dependencies. No configuration server required. You don't even need a Ruby runtime on the remote server.

Install:

$ [sudo] gem install sunzi-rails

Go into your Rails project directory, then:

$ sunzi-cap create

It generates a config/sunzi folder along with subdirectories and templates. Inside sunzi, there are sunzi.yml and install.sh. Those two are the most important files that you mainly work on.

Go into your config/deploy.rb and make sure to have these set:

set :ruby_version, IO.read("#{File.dirname(__FILE__)}/../.ruby-version").strip
set :admin_name, 'deployer'
set :deployer_name, 'deployer'

Go into your config/deploy/[stage].rb and make sure to have these set:

set :server, 'example.com'
server fetch(:server), user: fetch(:deployer_name), roles: %w[app web db]

Go into your config/secrets.yml and make sure to have these set:

[stage]:
  deployer_password: password
  deployer_public_key: "ssh-rsa ...== deployer@example.com"

Finally, add /compiled to your .gitignore file.

All those settings can be overriden in your sunzi.yml file within attributes.

Also, deploy.rb, deploy/[stage].rb, database.yml (prefixed with db_), secrets.yml and contextual attributes (prefixed with env_) are available through @attributes:

@attributes.env_stage
@attributes.env_role
@attributes.env_sudo
@attributes.env_user
@attributes.env_host
@attributes.env_port

It's important to note that deploy.rb and deploy/[stage].rb are loaded in that order and that variables defined within deploy/[stage].rb aren't available within deploy.rb.

Go into the project directory, then run sunzi-cap deploy:

$ sunzi-cap deploy staging deployer --sudo

Now, what it actually does is:

1. Compile sunzi.yml to generate attributes and retrieve remote recipes, then copy files scoped to admin role into the compiled directory
2. SSH to user@example.com defined within your Cpistrano config/deploy/staging.rb file
3. Transfer the content of the compiled directory to the remote server and extract in $HOME/sunzi
4. Run install.sh on the remote server with sudo mode turned on
5. Idem for the deployer role, but with sudo mode turned off

As you can see, all you need to do is edit install.sh and add some shell commands. That's it.

A Sunzi project without any recipes or roles is totally fine, so that you can start small, go big as you get along.

$ sunzi-cap                                  # Show command help
$ sunzi-cap create                           # Create a new Sunzi project
$ sunzi-cap compile [stage] [role] [--sudo]  # Compile Sunzi project
$ sunzi-cap deploy [stage] [role] [--sudo]   # Deploy Sunzi project

Here's the directory structure that sunzi-cap create automatically generates:

compiled/         # everything under this folder will be transferred to the
                  # remote server (do not edit directly)
config/sunzi/
  install.sh      # main script
  sunzi.yml       # add custom attributes and remote recipes here

  recipes/        # put commonly used scripts here, referred from install.sh
    sunzi.sh
  roles/          # when role is specified, scripts here will be concatenated
    db.sh         # to install.sh in the compile phase
    web.sh
  files/          # put any files to be transferred

There are two ways to pass dynamic values to the script - ruby and bash.

For ruby: In the compile phase, attributes defined in sunzi.yml are accessible from any files in the form of <%= @attributes.ruby_version %>.

For bash: In the compile phase, attributes defined in sunzi.yml are split into multiple files in compiled/attributes, one per attribute. Now you can refer to it by $(cat attributes/ruby_version) in the script.

For instance, given the following install.sh:

echo "Goodbye <%= @attributes.goodbye %>, Hello <%= @attributes.hello %>!"

With sunzi.yml:

attributes:
  goodbye: Chef
  hello: Sunzi

Now, you get the following result.

Goodbye Chef, Hello Sunzi!

Recipes can be retrieved remotely via HTTP. Put a URL in the recipes section of sunzi.yml, and Sunzi will automatically load the content and put it into the compiled/recipes folder in the compile phase.

For instance, if you have the following line in sunzi.yml,

recipes:
  rvm: https://raw.github.com/kenn/sunzi-recipes/master/ruby/rvm.sh

rvm.sh will be available and you can refer to that recipe by source recipes/rvm.sh.

You may find sample recipes in this repository useful: https://github.com/kenn/sunzi-recipes

You probably have different configurations between web servers and database servers.

No problem - how Sunzi handles role-based configuration is refreshingly simple.

Shell scripts under the roles directory, such as web.sh or db.sh, are automatically recognized as a role. The role script will be appended to install.sh at deploy, so you should put common configurations in install.sh and role specific procedures in the role script.

For instance, when you set up a new web server, deploy with a role name:

sunzi-cap deploy production web

It is equivalent to running install.sh, followed by web.sh.

If you're using Sunzi with Vagrant, make sure that you have a root access via SSH.

After vagrant up, connect with vagrant ssh and add your public ssh key id_rsa.pub to ~/.ssh/authorized_keys.

$ sunzi-cap deploy vagrant deployer