When you use Chef cookbook, a lot of files might be installed in you machine, configuration, script and so on. Chef provides very useful resource for putting a file called template. You can put any type of text file with this resource.

Template Resource

But template does not manage a file when it is unused. How can we delete a file once installed? Since there is no way provided by Chef, we have to implement. So here I want to introduce a small pattern to achieve this purpose here. The problem we want to solve here is this.

  • We have a dynamic list of files to be installed
  • We have to change the list anytime even some of them are deleted
  • Deleted files from the list must be also deleted from the machine

We can assume the case that the list is kept by data_bags or consul. Chef template cannot handle this type of dynamic list flexibly itself. So this is what I’ve written to achieve this.

def installed_config_files
    return []

This is defined in libraries or somewhere. installed_config_files is used in each recipe.

installed_config_files.each do |conf|
  # Check the installed file should be kept or not
  if !config_files.include?(conf) then
    file conf do
      action :delete

config_files.each do |conf|
  template conf do
    source somewhere
    action :create

With this snippet, you can make sure only the filed defined config_files are installed in the target machine. Chef provides great power to our non-operation intensive engineers. I realized again that I can do operations which can be repeatable, persistent and writable. I want to be more familiar with Chef usage further.

Thank you.