Getting Started with Chef: Working with Files

Chef: Infrastructure as Code, Automation, Configuration Management, having a service that can do that, and especially having something in place that knows what the desired state of your configurations/applications should be is definitely a plus.

I stumbled upon learn.chef.io which is a great resource for learning chef, as I am learning Chef at this moment.

The Components of Chef consists of:

Chef Workstation (ChefDK enables you to use the tools locally to test before pushing your code to the Chef Server)
Chef Server (Central Repository for your Cookbooks and info of every node Chef Manages)
Chef Client (a Node that is Managed by the Chef Server)

In this post we will install the Chef Development Kit, and work with the chef-client in local-mode to create, update and delete files using the file resource type.

Getting Started with Chef: Installation:

Installing the Chef Development Kit:

$ sudo apt-get update && apt-get upgrade -y
$ sudo apt-get install curl git -y
$ curl https://omnitruck.chef.io/install.sh | sudo bash -s -- -P chefdk -c stable -v 2.0.28

Configure a Resource:

Using chef-client in local mode, we will use the resource: file to create a recipe that will create our motd file

file '/tmp/motd' do
  content 'hello world'
end

Running chef client against our recipe in local-mode:

$ chef-client --local-mode hello.rb
..
Converging 1 resources
Recipe: @recipe_files::/root/chef-repo/hello.rb
  * file[/tmp/motd] action create
    - create new file /tmp/motd
    - update content in file /tmp/motd from none to b94d27
    --- /tmp/motd       2017-09-04 16:18:19.265699403 +0000
    +++ /tmp/.chef-motd20170904-4500-54fh8w     2017-09-04 16:18:19.265699403 +0000
    @@ -1 +1,2 @@
    +hello world

Verify the Content:

$ cat /tmp/motd
hello world

Running the command again will do nothing, as the content is in its desired state:

$ chef-client --local-mode hello.rb
..
Converging 1 resources
Recipe: @recipe_files::/root/chef-repo/hello.rb
  * file[/tmp/motd] action create (up to date)

Changing our recipe by replacing the word world with chef, we will find that the content of our file will be updated:

$ chef-client --local-mode hello.rb
..
Converging 1 resources
Recipe: @recipe_files::/root/chef-repo/hello.rb
  * file[/tmp/motd] action create
    - update content in file /tmp/motd from b94d27 to c38c60
    --- /tmp/motd       2017-09-04 16:18:19.265699403 +0000
    +++ /tmp/.chef-motd20170904-4903-wuigr      2017-09-04 16:23:21.379649145 +0000
    @@ -1,2 +1,2 @@
    -hello world
    +hello chef

Let's overwrite the content of our motd file manually:

$ echo 'hello robots' > /tmp/motd

Running Chef Client against our recipe again, allows Chef to restore our content to the desired state that is specified in our recipe:

$ chef-client --local-mode hello.rb
..
Converging 1 resources
Recipe: @recipe_files::/root/chef-repo/hello.rb
  * file[/tmp/motd] action create
    - update content in file /tmp/motd from 548078 to c38c60
    --- /tmp/motd       2017-09-04 16:24:29.308286834 +0000
    +++ /tmp/.chef-motd20170904-5103-z16ssa     2017-09-04 16:24:42.528021632 +0000
    @@ -1,2 +1,2 @@
    -hello robots
    +hello chef

Deleting a file from our recipe:

file '/tmp/motd' do
  action :delete
end

Now using chef client to execute against this file will remove our file:

$ chef-client --local-mode destroy.rb
Recipe: @recipe_files::/root/chef-repo/destroy.rb
  * file[/tmp/motd] action delete
    - delete file /tmp/motd

Getting Started with Chef: Installation:

Configure a Resource:

Resources: