packer/command/test-fixtures/provisioners/provisioner-override.json

{
  "builders": [
    {
      "type": "null",
      "name": "example1",
      "communicator": "none"
    },
    {
      "type": "null",
      "name": "example2",
      "communicator": "none"
    }
  ],
  "provisioners": [
    {
      "type": "shell-local",
      "inline": ["echo not overridden"],
      "override": {
        "example1": {
          "inline": ["echo yes overridden"]
        }
      }
    }
  ]
}