Description

The overridable cookbook provides an LWRP that makes it simple to provide maximum user flexibility in cookbook templates. When used instead of the standard Template resource (http://wiki.opscode.com/display/chef/Resources#Resources-Template), it provides a means for a cookbook user to override each template with either the user's own template or a concrete file.

Attributes

• node['overridable']['template']['enabled'] - Default: true. Setting to false passes through to the standard Template behavior
• node['overridable']['template']['files_enabled'] - Default: true. Setting to false disables the ability to override from files
• node['overridable']['template']['templates_enabled'] - Default: true. Setting to false disables the ability to override existing templates with new templates

Usage

Cookbook Authors

To use the LWRP in your cookbook, simply add depends 'overridable' to the cookbook's metadata.rb and substitute any template resources with overridable_template

Cookbook Users

When config file customization is needed on a cookbook that takes advantage of overridable template, two options are available:

Custom template

Copy the cookbook's provided template file to a new file of the same name within the cookbook's templates/overrides directory. Ex: templates/default/web_app.conf.erb maps to templates/default/overrides/web_app.conf.erb Additional attributes can be set in a new attributes file added to the cookbook attributes/ directory and referenced through the @node reference exposed to the Erb template. File-specificity rules are honored, so the override/ path can exist in a host-specific directory instead for instance.

Custom file

A file can replace the template behavior entirely (ensure you have dealt with any dynamic aspect of the config you're replacing). The file must be named the same as the destination path of the template resource Ex: /etc/ntp.conf would be named ntp.conf within the cookbook's files/ directory

Todo

• Multiple overridable_template calls that refer to the same base filename within separate paths will all be overridden by the same file with no way to separate them out
• Given the name of the cookbook, other wrappers could make sense as well (file?)

License and Author

Author:: Michael Leinartas ([email protected])

Copyright 2011, Michael Leinartas

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.