Automate your server configuration with Chef

A look at the Chef ecosystem and what's required to get started using chef to setup repeatable server environments and maintain stability across multiple environments

Transcript

1. Automate your server configuration with Chef Jeremy Olliver @static_storm
2. Why? • Sooner or later, you will need to repeat or change the setup • If you have to document it, make it an executable one • Faster to setup additional servers • Share knowledge (or at least make it portable)
3. What is chef? • chef is a configuration management system • define snippets of configuration as cookbooks • chef-client pulls down what changes to make and runs them • chef-server is a merb rest web app backed by solr, couchdb
4. Chef Concepts • Cookbook - the actual ruby code that determines how to install/configure something • Node - each server you are configuring is a node • Role - A collection of cookbooks to run, may override attributes • environment - Similar to Role, though every node belongs to one environment.
5. Cookbooks • community hosted cookbooks are online at: http://community.opscode.com/cookbooks/ rubygems.org of cookbooks • mostly good, but always read before using them. • install off github easily • create your own
6. knife • knife is the command line tool for interacting via the api • Each component is uploaded through knife • knife cookbook upload <name> [--freeze] • knife environment|role from file <path> • create cookbooks, integrate with cloud services • some rake tasks to simplify uploading everything
7. Bootstrapping & Auth • Uses a master ssh key validation.pem to authenticate clients • knife has a bootstrap script which over ssh does: • install chef client, copies the validation.pem across • validates a new client key with validation.pem • triggers the first chef-client run • bootstrap <ipaddress> -x user -E ‘staging’ -r ‘role [ruby_app]’ --sudo
8. Anatomy of a chef run • client connects to server, authenticating with pub key • checks run_list, downloads required cookbooks • compliation phase, defines resources, sets attributes • execution phase, resources are executed
9. Attributes precedence order • automatic (what chef detects), override, normal, default • set via: cookbooks, environments, roles, nodes default attributes applied in an attributes file default attributes applied in an environment default attributes applied in a role default attributes applied on a node directly in a recipe normal or set attributes applied in an attributes file normal or set attributes applied on a node directly in a recipe override attributes applied in an attributes file override attributes applied in a role override attributes applied in an environment override attributes applied on a node directly in a recipe automatic attributes generated by Ohai
10. Resource Types • File: copies a file • Template: Creates a file from an ERB template • directory, user, service • can notify other resources (restart when config file changed) • create custom ones via resources/providers
11. Creating cookbooks • Creating things specific to your application will require a cookbook (cookbooks are the only dynamic code) • knife cookbook create <name> • Specify dependencies and version number in metadata.rb • recipes/default.rb is the bare minimum you need • most simple cookbooks will just need recipes, attributes, and maybe files/templates
12. Knife plugins • knife-spork (version management through environments) • knife-essentials • librarian (bundler for cookbooks) • foodcritic (best practice guides for writing cookbooks)
13. Chef good practice • Version your cookbooks, specify versions in environments • Specify cookbook sources (librarian or Berkfile) • keep chef-client running periodically (chef-client cookbook) • avoid automatic (set/stored) attributes unless necessary • keep a balance between composability and unversioned roles • Freeze cookbook versions, and use VM’s to test (vagrant)
14. Resources • http://community.opscode.com/cookbooks/ • http://wiki.opscode.com/display/chef • irc.freenode.net #chef
15. Automate your server configuration with Chef Jeremy Olliver @static_storm