terraform/website/docs/provisioners/null_resource.html.markdown

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---
layout: "docs"
page_title: "Provisioners Without a Resource"
sidebar_current: "docs-provisioners-null-resource"
description: |-
The `null_resource` is a resource allows you to configure provisioners that
are not directly associated with a single existing resource.
---
# Provisioners Without a Resource
[null]: /docs/providers/null/resource.html
If you need to run provisioners that aren't directly associated with a specific
resource, you can associate them with a `null_resource`.
Instances of [`null_resource`][null] are treated like normal resources, but they
don't do anything. Like with any other resource, you can configure
[provisioners](/docs/provisioners/index.html) and [connection
details](/docs/provisioners/connection.html) on a `null_resource`. You can also
use its `triggers` argument and any meta-arguments to control exactly where in
the dependency graph its provisioners will run.
## Example usage
```hcl
resource "aws_instance" "cluster" {
count = 3
# ...
}
resource "null_resource" "cluster" {
# Changes to any instance of the cluster requires re-provisioning
triggers = {
cluster_instance_ids = "${join(",", aws_instance.cluster.*.id)}"
}
# Bootstrap script can run on any instance of the cluster
# So we just choose the first in this case
connection {
host = "${element(aws_instance.cluster.*.public_ip, 0)}"
}
provisioner "remote-exec" {
# Bootstrap script called with private_ip of each node in the cluster
inline = [
"bootstrap-cluster.sh ${join(" ", aws_instance.cluster.*.private_ip)}",
]
}
}
```
## Argument Reference
In addition to meta-arguments supported by all resources, `null_resource`
supports the following specific arguments:
* `triggers` - A map of values which should cause this set of provisioners to
re-run. Values are meant to be interpolated references to variables or
attributes of other resources.