Policyfiles are used to combine the advantages of roles and environment with Berkshelf.In usual Chef Workflow, the versions and the LOCATIONS of COOKBOOKS being used by a Chef Client are updated in “metadata.rb” file and “Berksfile”. Often this is a tedious task and a SMALL error in these FILES make Chef Client apply the wrong cookbook and converged node would not acquire the required state. These problems could be solved by using a single document called Policyfiles to get the specific cookbook revisions and recipes that Chef Infra Client would apply. Policyfiles are applied on a GROUP of nodes, cookbooks or settings. The syntax for a Policyfile.rb file is as follows:

where 

• “name” is the name of the policy
• “run_list “ is the list of recipes applied by Chef Client on all nodes associated with the policy
• “default_source” specifies the location of the cookbook
•  “cookbook” defines the name of the cookbook and version constraints. An alternate source path for the cookbook could also be specified here.