A library for creating machines and infrastructures idempotently in Chef.
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Stories in Ready Chef Metal

This library solves the problem of repeatably creating machines and infrastructures in Chef. It has a plugin model that lets you write bootstrappers for your favorite infrastructures, including VirtualBox, EC2, LXC, bare metal, and many more!

This video explains the basics of chef-metal (though provisioners are now called drivers). Slides (more up to date) are here.

Date Blog
6/3/2014 machine_batch and parallelization
6/3/2014 Chef Metal, Configuration and Drivers
3/4/2014 Chef Metal 0.2: Overview - this is a pretty good overview (though dated).
12/20/2013 Chef Metal Alpha


Try It Out

You can try out Metal in many different flavors.

HINT: chef-metal looks prettiest with chef 11.14 alpha. gem install chef --pre to get it.


To give it a spin, install Vagrant and VirtualBox and try this from the chef-metal/docs/examples directory:

gem install chef-metal chef-metal-vagrant
export CHEF_DRIVER=vagrant
chef-client -z vagrant_linux.rb simple.rb

This will create two vagrant precise64 linux boxes, "mario" and "luigi1", in ~/machinetest, bootstrapped to an empty runlist. For Windows, you can replace myapp::linux with myapp::windows, but you'll need your own Windows vagrant box to do that (licensing!).


If you have an AWS account, you can spin up a machine there like this:

gem install chef-metal chef-metal-fog
export CHEF_DRIVER=fog:AWS
chef-client -z simple.rb

This will create two linux boxes in the AWS account referenced by your default profile in ~/.aws/config (or your environment variables).


If you are on DigitalOcean and using the tugboat gem, you can do this:

gem install chef-metal chef-metal-fog
export CHEF_DRIVER=fog:DigitalOcean
chef-client -z simple.rb

If you aren't using the tugboat gem, you can put driver and driver_options into your .chef/knife.rb file.

This will use your tugboat settings to create whatever sort of instance you normally create.

Cleaning up

When you are done with the examples, run this to clean up:

chef-client -z destroy_all.rb

What Is Chef Metal?

Chef Metal has two major abstractions: the machine resource, and drivers.

The machine resource

You declare what your machines do (recipes, tags, etc.) with the machine resource, the fundamental unit of Chef Metal. You will typically declare machine resources in a separate, OS/provisioning-independent file that declares the topology of your app--your machines and the recipes that will run on them.

The machine resources from the example myapp::small are pretty straightforward. Here's a copy/paste:

machine 'mario' do
  recipe 'postgresql'
  recipe 'mydb'
  tag 'mydb_master'

num_webservers = 1

1.upto(num_webservers) do |i|
  machine "luigi#{i}" do
    recipe 'apache'
    recipe 'mywebapp'

You will notice the dynamic nature of the number of web servers. It's all code, your imagination is the limit :)


Drivers handle the real work of getting those abstract definitions into real, physical form. They handle the following tasks, idempotently (you can run the resource again and again and it will only create the machine once--though it may notice things are wrong and fix them!):

  • Acquiring machines from the cloud, creating containers or VMs, or grabbing bare metal
  • Connecting to those machines via ssh, winrm, or other transports
  • Bootstrapping chef onto the machines and converging the recipes you suggested

The driver API is separated out so that new drivers can be made with minimal effort (without having to rewrite ssh, tunneling, bootstrapping, and OS support). But to the user, they appear as a single thing, so that the machine acquisition can use its smarts to autodetect the other bits (transports, OS's, etc.).

Drivers save their data in the Chef node itself, so that they will be accessible to everyone who is using the Chef server to manage the nodes.

Drivers each have their own repository. Current drivers:




  • LXC (not yet up to date with 0.11)
  • Docker (not yet up to date with 0.11)

Bare Metal:

Anatomy of a Recipe

chef-zero comes with a provisioner for Vagrant, an abstraction that covers VirtualBox, VMWare and other Virtual Machine drivers. In docs/examples, you can run this to try it:

export CHEF_DRIVER=vagrant
chef-client -z vagrant_linux.rb simple.rb

This is a chef-client run, which runs multiple recipes. Chef Metal is nothing but resources you put in recipes.

The driver is specified on the command line. Drivers are URLs. You could use vagrant:~/vms or `fog:AWS:default:us-east-1' as driver URLs. More information here.

The vagrant_linux.rb recipe handles the physical specification of the machines and Vagrant box:

require 'chef_metal_vagrant'

vagrant_box 'precise64' do
  url 'http://files.vagrantup.com/precise64.box'

with_machine_options :vagrant_options => {
  'vm.box' => 'precise64'

require 'chef_metal_vagrant' is how we bring in the vagrant_box resource.

vagrant_box makes sure a particular vagrant box exists, and lets you specify machine_options for things like port forwarding, OS definitions, and any other vagrant-isms.

Typically, you declare these in separate files from your machine resources. Chef Metal picks up the drivers and machine_options you have declared, and uses them to instantiate the machines you request. The actual machine definitions, in this case, are in simple.rb, and are generic--you could use them against Azure or EC2 as well:

machine 'mario' do
  tag 'itsame'

Other directives, like recipe 'apache', help you set run lists and other information about the machine.

Fog (EC2, Openstack and friends)

chef-metal also comes with a Fog provisioner that handles provisioning to Openstack, Rackspace, Amazon's EC2 and other cloud drivers. Before you begin, you will need to put your AWS credentials in ~/.aws/config in the format mentioned in Option 1 here. There are other ways to specify your credentials, but this is the standard one for the Amazon CLI.

Once your credentials are in, basic usage looks like this:

export CHEF_DRIVER=fog:AWS
chef-client -z simple.rb

Other valid URLs include fog:AWS:myprofilename and fog:AWS:profilename:us-west-2.

Most Chef Metal drivers try hard to provide reasonable defaults so you can get started easily. Once you have specified your credentials, AMIs and other things are chosen for you.

You will usually want to create or input a custom key pair for bootstrap. To customize, specify keys and AMI and other options, you can make recipes like this:

require 'chef_metal_fog'

fog_key_pair 'my_bootstrap_key'

with_machine_options :bootstrap_options => {
  :key_name => 'my_bootstrap_key',
  :image_id => 'ami-59a4a230',
  :flavor_id => 't1.micro'

fog_key_pair creates a new key pair (if the files do not already exist) and uploads it to AWS (it will toss an error if the key pair already exists and does not match). By default, fog_key_pair will look for matching key files in .chef/keys, ~/.chef/keys and ~/.ssh. If it does not find one, it will place the key in .chef/keys. You can override this path in fog_key_pair, but if you do, you will want to modify private_key_paths in your configuration to match.

with_machine_options specifies machine_options that will be applied to any machine resources chef-client encounters.

You will notice that we are still using simple.rb here. Machine definitions are generally driver-independent. This is an important feature that allows you to spin up your clusters in different places to create staging, test or miniature dev environments.

Pointing Boxes at Chef Servers

By default, Chef Metal will put your boxes on the same Chef server you started chef-client with (in the case of -z, that's a local chef-zero server). Sometimes you want to put your boxes on different servers. There are a couple of ways to do that:

with_chef_local_server :chef_repo_path => '~/repo'

with_chef_local_server is a generic directive that creates a chef-zero server pointed at the given repository. nodes, clients, data bags, and all data will be stored here on your provisioner machine if you do this.

You can use with_chef_server instead if you want to point at OSS, Hosted or Enterprise Chef, and if you don't specify a Chef server at all, it will use the one you are running chef-client against. Keep in mind when using with_chef_server and running chef-client -z on your workstation that you will also need to set the client name and signing key for the chef server. If you've already got knife.rb set up, then something like this will correctly create a client for the chef server on instance using your knife.rb configuration:

with_chef_server "https://chef-server.example.org",
  :client_name => Chef::Config[:node_name],
  :signing_key_filename => Chef::Config[:client_key]

Note for Hosted/Enterprise Chef Servers

Currently, you will need to add the 'clients' group to the 'admin' group in order for machine provisioning to work:

knife edit /groups/admin.json -e <editor>

Then add:

  "users": [
    "pivotal" # This is an internal superuser for Hosted/Enterprise Chef
  "groups": [
    "clients" # This is what you need to add

This can also be done through the Chef Server web UI (Administration tab > Groups > select admins Group > Add 'clients'


Chef Metal also works with Test Kitchen, allowing you to test entire clusters, not just machines! The repository for the kitchen-metal gem is https://github.com/doubt72/kitchen-metal.

Bugs and The Plan

Please submit bugs, gripes and feature requests at https://github.com/opscode/chef-metal/issues, contact jkeiser on Twitter at @jkeiser2, email at jkeiser@getchef.com

To contribute, just make a PR in the appropriate repo--also, make sure you've signed the Chef Contributor License Agreement (quick couple of minutes online), since this is going into core Chef eventually. It takes some time to process, so if you've just done it, let me know in the PR :) If you already signed this for a Chef contribution, you don't need to do so again--if you're not sure, you can check for your name here!