Intro to Chef

What is Chef?

a configuration management tool from Opscode

what is configuration management?

Configuration Management

in general, how a "system" should be configured and maintained

for Chef, how servers are configured

can be:

• network settings
• services provided
• software settings
• etc

so...

What is Chef?

• set of tools to manage servers
• provides Ruby framework for describing configuration

Mantra

what?

Meaning

manage the infrastructure running your code the same way you manage your code

Resource

• a reusable component for use in recipes
• provides some function, does some action
• depends on a provider to adapt the action for the platform
• may have many providers for many different platforms
• is a Ruby class that extends base Chef resource and provider

Example Resources

• directory
• remote_file
• package
• bash

Recipe

• set of tasks to perform using resources
• may be included in other recipes
• may use node attributes
• must be idempotent
• is a Ruby script

Example Recipe

# Cookbook name:: your_app
# Recipe:: default

remote_file "/tmp/thing/tarball.tar.gz" do
  action :create
  source "http://example.com/your/tarball.tar.gz"
  backup false
  mode "0755"
end

execute "unarchive tarball for install" do
  cwd '/tmp/thing'
  command "tar zxf tarball.tar.gz -C #{node[:your_app][:dir]} && rm tarball.tar.gz"
  only_if {::File.file?("/tmp/tarball.tar.gz")}
end

template "/etc/init.d/your_app" do
  owner "root"
  group "root"
  source "your_app.erb"
  mode "0755"
end

service "your_app" do
  supports status: true, restart: true
  action :enable
end

service "your_app" do
  action :restart
end
            

Cookbook

• a distributable collection of components needed to run one or more recipes
• may include:
  • resources, providers
  • recipes
  • node attributes
  • files / templates
  • etc
• are versioned
• are folders with files in a specific structure

Cookbook Layout

/path/to/your_cookbook
├── README.md
├── attributes
├── definitions
├── files
│   └── default
├── libraries
├── metadata.rb
├── providers
├── recipes
│   └── default.rb
├── resources
└── templates
    └── default
            

Role

• describes a service or functionality for the node to have
  • web server (configure Apache)
  • database server (configure PostgreSQL)
  • etc
• has attributes related to the functionality
• has a run list with one or more recipes
• is a Ruby script

Example Role

name "your_app_prod"
description "Deploys your_app in the production environment"

run_list(
  "recipe[your_app_backend]",
  "recipe[your_app_frontend]"
)

override_attributes(
  :your_app_backend => { :port = 4242 },
  :important_dependency => {
    :some_setting => true,
    :other_setting => "/path/to/cool/file"
  }
)
            

Chef Server

• common management endpoint
• configure through CLI or web UI
• keeps a database of everything
• register nodes to the server
• register users (clients) to manage the server
• clients upload roles, cookbooks

Chef Client

• command run on node
• only available after bootstrapping
• syncs roles, run list for the current node
• executes run list

Knife

• the workstation CLI configuration tool
• used to manage nodes, cookbooks, roles, etc.
• used to bootstrap new nodes

is that it?

there are a few other components

(data bags, environments, ...)

and best practices

but that's for another time