Recipe : Recipes are nothing but the simple ruby code to manage the system (Nodes). Each recipe is mapped to a provider and Provider completes the action with required steps. And then resources get processed. This phase is called execution phase.


Resources: Each system has multiple components and each component is handle by resource, so resource is component configuration policy
It could be a file, cronjob, service, package
 A resource comes with four component :   A type, A name, Attributes, Actions
  So structure would be :
   type "name" do
    attribute "value"
    action :action_type
 end
 Note: Every action has its default value, example: package resource default action is :install
            package "httpd"  equivalent to =>   package "httpd" do
            action :install
           end
Here, package is a type and httpd is a name.

Lets look at some actions
Action
:install               Does the installation of the resource
:nothing  It defines a resource that does nothing. 
Resource example with attribute:
service "httpd" do
action :start
                                                        retries 3
  ignore_failure true
end
Resource of type service and name is httpd will get started as per the defined action. If service is not getting started then still your chef run will not fail as per the defined attribute ignore_failure.


Cookbook: bundle all the recipes and store on chef server

Provider: To make sure that resources are handled in right manner, so there are different providers for different resources

When we right a code to install a package then provider is chosen according to the target platform. And platform is chosen by Ohai. Ohai is a ruby gem installed with chef itself.

Running the Ohai command on my machine for reference:



chef-client: it handled the process of recipes (cookbbok) in two phases.
                    First Phase: All the recipes are added in run_list  would be added in container
                    Second Phase: All the libraries are loaded with all dependencies. this is called        
                    compilation phase




Guard Attributes: Guard attributes are basically defined to check weather the desired state is present or not for the Chef resource. If the desire state is already presents then chef resource does nothing for the same resource.
it would be a string or a block of ruby code as a value
Block of ruby code may return true or false
String as a value may return 0 (means exit status) 

   
     Attribute
not_if if true, dont execute the resource
only_if if true, then execute the resource

And we can use the argument with these attributes as below:


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Next part is coming soon .....