“metadata.rb” file is at the top level of every cookbook directory and gets created as soon as a cookbook is created. (For JAVA programmers the concept is similar to a CONSTRUCTOR getting created when an object is created!) It specifies all the dependencies required to correctly deploy a cookbook to its nodes. The Chef server compiles this metadata.rb file into metadata.json file and stores it. We can edit the metadata in the metadata.rb file and should be RECOMPILED every time by the Chef server for the changes to be IMPLEMENTED. Metadata.rb file is compiled when

1. A cookbook is uploaded to the Chef server
2. when the cookbook metadata knife subcommand is RUN and
3. when "knife cookbook create" subcommand is run, then the knife creates metadata.rb file automatically.

Metadata.rb files have entries under ‘depends’ keyword which specifies the different dependencies required to successfully deploy the cookbook in a specific node. If these dependencies are not given properly we may often face errors while DEPLOYING cookbooks and Chef nodes would not be configured as expected. Apart from "depends", we have other details given in the metadata.rb file like license, version, gem, etc. which can be parametrized using different operators (=,>=, >, etc)