DevOps Classroom Series – 09/Nov/2021

Attributes in Chef

• If we create variables in the recipe, changes to the variables might need change in cookbook versions, if we want to handle the variables in such a way that without uploading new version of cookbook if we can change variable values it would be better.
• In chef for this we have attributes.
• Attributes in Chef can be set from
  • recipe
  • attribute file in cookbook
  • roles
  • environment
• Creating an attribute file in chef cookbook
  • Exploring command line
  • Lets create the attribute file
• For adding attributes we need to follow the following syntax

<attribute_type>['attribute-name']='value'

• For now we will be using only one attribute type default and we will be following the convention

default['cookbook_name']['attribute_name'] = 'value'

• To use the attributes in the recipe file replace default with node

node['cookbook_name']['attribute_name']

• Refer Here this changeset for the changes done to accomodate attributes.

Chef Infra Language checking platforms

• Refer Here for the official documentation
• Refer Here for the changes using chef infra language checking platforms
• Refer Here for returning a value based on platform & its version and Refer Here for the changeset containing the changes

Common Resource Functionality: Gaurds

• Every resource in chef can have two properties only_if and not_if which gets executed during converge
• A gaurd property accepts either string value of ruby block
• Refer Here for the changeset and Refer Here for the documentation.

Common Resource Functionality: Notifications

• Refer Here for the official docs
• The syntax for notification
  • notifies: `notifies :action, ‘resource[name]’, :timer
• Refer Here for usage of notifies