Using environments

Having separate environments for development, testing, and production is a good way to be able to develop and test cookbook updates, and other configuration changes in isolation. Chef enables you to group your nodes into separate environments so as to support an ordered development flow.

Getting ready

For the following examples, let's assume that you have a node named server in the _default environment and that you have at least one cookbook (I'll use the ntp cookbook) registered with your Chef server.

How to do it…

Let's see how to manipulate environments using knife:

Note

This is only a good idea if you want to play around. For serious work, please create files describing your environments and put them under version control as described in the There's more… section of this recipe.

1. Create your environment on-the-fly using knife. The following command will open your shell's default editor so that you can modify the environment definition:

   Note

   Make sure you've set your EDITOR environment variable to your preferred one.

   mma@laptop:~/chef-repo $ knife environment create dev
   {
     "name": "dev",
     "description": "",
     "cookbook_versions": {
     },
     "json_class": "Chef::Environment",
     "chef_type": "environment",
     "default_attributes": {
     },
     "override_attributes": {
     }
   }
   Created dev
   

2. List the available environments:

   mma@laptop:~/chef-repo $ knife environment list
   _default
   dev
   

3. List the nodes for all the environments:

   mma@laptop:~/chef-repo $ knife node list
   server
   

4. Verify that the node server is not in the dev environment yet by listing nodes in the dev environment only:

   mma@laptop:~/chef-repo $ knife node list -E dev
   mma@laptop:~/chef-repo $
   

5. Change the environment of the server to dev using knife:

   mma@laptop:~/chef-repo $ knife node environment set server book
   server:
     chef_environment: dev
   

6. List the nodes in the dev environment again:

   mma@laptop:~/chef-repo $ knife node list -E dev
   server
   

7. Use specific cookbook versions and override certain attributes for the environment:

   mma@laptop:~/chef-repo $ knife environment edit dev
   {
     "name": "dev",
     "description": "",
     "cookbook_versions": {
       "ntp": "1.6.8"
     },
     "json_class": "Chef::Environment",
     "chef_type": "environment",
     "default_attributes": {
     },
     "override_attributes": {
       "ntp": {
         "servers": ["0.europe.pool.ntp.org", "1.europe.pool.ntp.org", "2.europe.pool.ntp.org", "3.europe.pool.ntp.org"]
       }
     }
   }
   Saved dev
   

How it works…

A common use of environments is to promote cookbook updates from development to staging and then into production. Additionally, they enable you to use different cookbook versions on separate sets of nodes and environment-specific attributes. You might have nodes with less memory in your staging environment as in your production environment. By using environment-specific default attributes, you can, for example, configure your MySQL service to consume less memory on staging than on production.

Note

The Chef server always has an environment called _default, which cannot be edited or deleted. All the nodes go in there if you don't specify any other environment.

Be aware that roles are not environment-specific. You may use environment-specific run lists, though.

The node's environment can be queried using the node.chef_environment method inside your cookbooks.

There's more…

If you want your environments to be under version control (and you should), a better way to create a new environment is to create a new Ruby file in the environments directory inside your Chef repository:

mma@laptop:~/chef-repo $ cd environments
mma@laptop:~/chef-repo $ subl dev.rb
name "dev"

You should add, commit, and push your new environment file to GitHub:

mma@laptop:~/chef-repo $ git add environments/dev.rb
mma@laptop:~/chef-repo $ git commit -a -m "the dev environment"
mma@laptop:~/chef-repo $ git push

Now, you can create the environment on the Chef server from the newly created file using knife:

mma@laptop:~/chef-repo $ knife environment from file dev.rb
Created environment dev

Tip

You have to deal with two artifact storages here. You have to use your version control system and knife / Berkshelf to sync your local changes to your Chef server. The Chef server is not aware of any changes that you do when using your version control system, and vice versa.

There is a way to migrate all the nodes from one environment to another by using knife exec:

mma@laptop:~/chef-repo $ knife exec -E 'nodes.transform("chef_environment:_default") { |n| n.chef_environment("dev")

You can limit your search for nodes in a specific environment:

mma@laptop:~/chef-repo $ knife search node "chef_environment:dev"
1 item found

See also

• If you want to set up a virtual machine as a node, see the Managing virtual machines with Vagrant recipe in this chapter
• Read more about environments at https://docs.chef.io/environments.html