Chef talk i gave back January 2011

2. Michael Richardson
Email: michael@energizedwork.com
2© 2011 Energized Work - www.energizedwork.com

3. Agenda
Chef Architecture
• Chef Server
• Chef Client
• Web UI
• Chef Solo
• Knife
Chef Basics
• Cookbooks
• Nodes
• Roles
• Attributes
Examples
Useful links
3© 2011 Energized Work - www.energizedwork.com

4. Chef Architecture
4© 2011 Energized Work - www.energizedwork.com

5. Chef Server – Architecture
5© 2011 Energized Work - www.energizedwork.com
Server components:
• Chef Server
• Chef Server Web UI
• CouchDB
• RabbitMQ
• Chef Solr Indexer
• Chef Solr
Client components:
• Chef Client
• Chef Solo
• Knife
• Shef

6. Chef Server
• Merb Web application
• API service
• Data stored with CouchDB
• Distributes cookbooks to Chef Clients
6© 2011 Energized Work - www.energizedwork.com

7. Chef Server Web UI
• Merb Web application
• Talks to Chef Server API service
• Data stored with CouchDB
7© 2011 Energized Work - www.energizedwork.com

8. Knife
• Command line interface to Chef
• Alternative to using the Chef-Server Web UI
• Allows you to create, list, edit and delete objects in Chef-Server
8© 2011 Energized Work - www.energizedwork.com

9. Chef Client
• Clients do all the work
• Communicates with Chef Server via REST
• Downloads, Compiles and Executes cookbooks
• Can run periodically as a daemon or as a single run
• Ohai (part of chef-client). Provides node information to Chef
9© 2011 Energized Work - www.energizedwork.com

10. Chef Basics
10© 2011 Energized Work - www.energizedwork.com

11. Nodes
• A node is a host that runs chef client
• Primary feature of a node are it’s attributes and it’s run list
• Nodes are made up of two prime components
• Recipes
• Roles
11© 2011 Energized Work - www.energizedwork.com

12. Nodes – Run List
• Run list is a list of the recipes that a node will run
• Order is important
• Can include roles which may have recipes assigned to them
12© 2011 Energized Work - www.energizedwork.com

13. Attributes
• Nodes and roles have associated attributes (key-value pairs)
• Node and role attributes are used as inputs for resource attributes
• Attributes maybe set on a node from the following objects
• Cookbooks
• Roles
• Nodes
13© 2011 Energized Work - www.energizedwork.com

14. Roles
• Compose functionality sets for nodes through recipes and attributes
• 2 workflows for managing roles
• Write Ruby or JSON files
• Use Knife or Web UI
14© 2011 Energized Work - www.energizedwork.com

15. Cookbooks
• Collection of files used to configure a system
/cookbook/
/attributes/
/definitions/
/files/
/libraries/
/metadata.rb
/README.rdoc
/recipes/
/templates/
• Each cookbook typically configures a single package of service
• Cookbooks are commonly shared in the Chef community
15© 2011 Energized Work - www.energizedwork.com

16. Cookbooks – Recipes
• Encapsulates resources (fundamental units in Chef)
• Resource:
16© 2011 Energized Work - www.energizedwork.com

17. Cookbooks – Recipes
• Basic examples of resources
17© 2011 Energized Work - www.energizedwork.com
package "tar" do
version "1.16.1-1"
action :install
end
remote_file "/tmp/testfile" do
source "http://build.ew/warfiles/testfile"
mode "0644"
checksum "08da002l"
end
service ”httpd" do
supports :status => true, :restart => true, :reload => true
action [ :enable, :start ]
end
cookbook_file "/tmp/testfile" do
source "testfile"
mode "0644"
end
directory "/tmp/something" do
owner "root"
group "root"
mode "0755"
action :create
end
template "/tmp/config.conf" do
source "config.conf.erb"
end
link "/tmp/passwd" do
to "/etc/passwd"
end

18. Cookbooks – Files and templates
• Files allow you to distribute files to your servers as part of cookbooks
• Templates are files that have been marked up to include variables
• To allow cookbooks to operate on multiple platforms, files and
templates can be found in a number of locations within a cookbook
18© 2011 Energized Work - www.energizedwork.com
Eg in order of priority.
cookbook/templates/webapp01.ew/sudoers.erb
cookbook/templates/ubuntu-8.04/sudoers.erb
cookbook/templates/ubuntu/sudoers.erb
cookbook/templates/default/sudoers.erb

19. Cookbooks – Template example
• Simple template resource
• Simple ERB template file – templates/default/foo.erb
• Rendered file on client
19© 2011 Energized Work - www.energizedwork.com
node[:fqdn] = ”webapp01.ew"
template "/tmp/foo" do
source "foo.erb"
variables({
:java_app => ”SomethingCool.war"
})
end
The node <%= node[:fqdn] %> is running the app <%= @java_app %>
# cat /tmp/foo
The node webapp01.ew is running the app SomethingCool.war
#

20. Useful links
• http://www.opscode.com/
• http://wiki.opscode.com/display/chef/Home
• http://wiki.opscode.com/display/chef/Resources
• http://cookbooks.opscode.com/
• https://github.com/37signals/37s_cookbooks
• https://github.com/opscode/cookbooks
20© 2011 Energized Work - www.energizedwork.com

21. Chef Examples
21© 2011 Energized Work - www.energizedwork.com

22. 22© 2011 Energized Work - www.energizedwork.com
Thank you
Email: michael@energizedwork.com