How to use user variables with file provisioner in Packer?

Question

I have a packer json like:

"builders": [{...}],
"provisioners": [
          {
                "type": "file",
                "source": "packer/myfile.json",
                "destination": "/tmp/myfile.json"
           }
  ],
"variables": {
        "myvariablename": "value"
 }

and myfile.json is:

{
   "var" : "{{ user `myvariablename`}}"
}

The variable into the file does get replaced, is a sed replacement with shell provisioner after the file the only option available here?

Using packer version 0.12.0

Answer 1

So far I've come just with the solution to use file & shell provisioner. Upload file and then replace variables in file via shell provisioner which can be fed from template variables provided by e.g. HashiCorp Vault

Answer 2

You have to pass these as environment variables. For example:

  "provisioners": [
    {
      "type": "shell"
      "environment_vars": [
        "http_proxy={{user `proxy`}}",
      ],
      "scripts": [
        "some_script.sh"
      ],
    }
  ],
  "variables": {
    "proxy": null
  }

And in the script you can use $http_proxy