Using environments

For the following examples, I 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.

Let's see how to manipulate environments using knife.

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 lesser 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 lesser memory on staging than on production.

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.

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 book.rb
name "book"

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

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

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

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

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("book")

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

mma@laptop:~/chef-repo $ knife search node "chef_environment:book"

1 item found