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Ohai detects data about your operating system. It can be used standalone, but it's primary purpose is to provide node data to Chef.

Ohai will print out a JSON data blob for all the known data about your system. When used with Chef, that data is reported back via node attributes.

Opscode distributes ohai as a RubyGem. This README is for developers who want to modify the Ohai source code. For users who want to write plugins for Ohai, see the wiki:


Before working on the code, if you plan to contribute your changes, you need to read the Opscode Contributing document.

You will also need to set up the repository with the appropriate branches. We document the process on the Chef Wiki.

(Substitude 'ohai' for 'chef')

Once your repository is set up, you can start working on the code. We do use BDD/TDD with RSpec, and soon Cucumber for integration/feature testing, so you'll need to get those installed.


In order to have a dev environment where you can work on Ohai, you'll need to install a few additional gems after setting up the Git repository.

Install the following RubyGems.

  • rake

  • rspec

  • extlib

  • systemu

  • json

    gem install rake rspec extlib systemu json

Rake Tasks

Ohai has some Rake tasks for doing various things.

rake -T
rake clobber_package  # Remove package products
rake gem              # Build the gem file ohai-$VERSION.gem
rake install          # install the gem locally
rake make_spec        # create a gemspec file
rake package          # Build all the packages
rake repackage        # Force a rebuild of the package files
rake spec             # Run specs

($VERSION is the current version, from the GemSpec in Rakefile)

Spec Testing:

We use RSpec for unit/spec tests.

rake spec

Because ohai gathers system information, and we don't know what kind of system we might be running on (yet), we're moving away from specs for integration testing and to cucumber.




(Use the OHAI project)



Ohai - system information application


Adam Jacob (<>)


Copyright © 2008 Opscode, Inc.


Apache License, Version 2.0

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

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.