A common use-case for applications is to have Chef configure your systems and use Capistrano to deploy the applications that run on them.
The Capistrano configuration has a facility to specify the roles for your application and which servers are members of those roles. Chef has its own roles. If you're using both Chef and Capistrano, you don't want to have to tell them both about which servers you'll be deploying to, especially if they change often.
capistrano-chef provides some helpers to query your Chef server from Capistrano to define these roles.
A normal deploy.rb in an app using capistrano defines a roles like this:
role :web, 10.0.0.1, 10.0.0.2
role :db, 10.0.0.3, :primary => true
Using capistrano-chef, you can do this:
require 'capistrano/chef'
chef_role :web "roles:web"
chef_role :db, "roles:database_master", :primary => true,
:attribute => :private_ip
This defines the same roles using Chef's search feature. Nodes are searched using the given query. The node's ipaddress attribute is used by default, but another (top-level) attribute can be specified in the options. The rest of the options are the same as those used by Capistrano.
Chef configuration options are loaded by Knife, looking for .chef/knife.rb in the current directory or one its parent directories.
To generate this file, run the following from the root of your project:
$ knife configure -i
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