Parameters common to all provisioners:

- `pause_before` (duration) - Sleep for duration before execution.

- `max_retries` (int) - Max times the provisioner will retry in case of failure. Defaults to zero (0). Zero means an error will not be retried.

- `only` (array of string) - Only run the provisioner for listed builder(s)
  by name.

- `override` (object) - Override the builder with different settings for a
  specific builder, eg :

  In JSON:
  ```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"]
          }
        }
      }
    ]
  }
  ```

  In HCL2:
  ```hcl
  source "null" "example1" {
    communicator = "none"
  }

  source "null" "example2" {
    communicator = "none"
  }

  build {
    sources = ["source.null.example1", "source.null.example2"]
    provisioner "shell-local" {
      inline = ["echo not overridden"]
      override = {
        example1 = {
          inline = ["echo yes overridden"]
        }
      }
    }
  }
  ```

- `timeout` (duration) - If the provisioner takes more than for example
  `1h10m1s` or `10m` to finish, the provisioner will timeout and fail.