Using attributes in Chef

Question

Just getting started with using chef recently. I gather that attributes are stored in one large monolithic hash named node that's available for use in your recipes and templates.

There seem to be multiple ways of defining attributes

Can somebody explain the precedence?

Answer 1

Attributes are defined by:

• The state of the node itself
• Cookbooks (in attribute files and/or recipes)
• Roles
• Environments

Attributes are always applied by the chef-client in the following order:

1. A default attribute located in a cookbook attribute file
2. A default attribute located in a recipe
3. A default attribute located in an environment
4. A default attribute located in a role
5. A force default attribute located in a cookbook attribute file
6. A force default attribute located in a recipe
7. A normal attribute located in a cookbook attribute file
8. A normal attribute located in a recipe
9. An override attribute located in a cookbook attribute file
10. An override attribute located in a recipe
11. An override attribute located in a role
12. An override attribute located in an environment
13. A force override attribute located in a cookbook attribute file
14. A force override attribute located in a recipe
15. An automatic attribute identified by Ohai at the start of the chef-client run

where the last attribute in the list is the one that is applied to the node.

Answer 2

Attributes are defined by:

• The state of the node itself
• Cookbooks (in attribute files and/or recipes)
• Roles
• Environments

Answer 3

There are 6 different types of attributes:

• default: A default attribute is automatically reset at the start of every chef-client run and has the lowest attribute precedence. Use defaultattributes as often as possible in cookbooks.
• force_default: Use the force_default attribute to ensure that an attribute defined in a cookbook (by an attribute file or by a recipe) takes precedence over a default attribute set by a role or an environment.
• normal: A normal attribute is a setting that persists in the node object. A normal attribute has a higher attribute precedence than a defaultattribute.
• override: An override attribute is automatically reset at the start of every chef-client run and has a higher attribute precedence than default, force_default, and normal attributes. An overrideattribute is most often specified in a recipe, but can be specified in an attribute file, for a role, and/or for an environment. A cookbook should be authored so that it uses override attributes only when required.
• force_override: Use the force_override attribute to ensure that an attribute defined in a cookbook (by an attribute file or by a recipe) takes precedence over an override attribute set by a role or an environment.
• automatic: An automatic attribute contains data that is identified by Ohai at the beginning of every chef-client run. An automatic attribute cannot be modified and always has the highest attribute precedence.