122 lines
4.1 KiB
Markdown
122 lines
4.1 KiB
Markdown
---
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layout: "docs"
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page_title: "Provisioners"
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sidebar_current: "docs-provisioners"
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description: |-
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Provisioners are used to execute scripts on a local or remote machine as part of resource creation or destruction.
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---
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# Provisioners
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Provisioners are used to execute scripts on a local or remote machine
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as part of resource creation or destruction. Provisioners can be used to
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bootstrap a resource, cleanup before destroy, run configuration management, etc.
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Provisioners are added directly to any resource:
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```hcl
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resource "aws_instance" "web" {
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# ...
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provisioner "local-exec" {
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command = "echo ${self.private_ip_address} > file.txt"
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}
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}
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```
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For provisioners other than local execution, you must specify
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[connection settings](/docs/provisioners/connection.html) so Terraform knows
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how to communicate with the resource.
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## Creation-Time Provisioners
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Provisioners by default run when the resource they are defined within is
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created. Creation-time provisioners are only run during _creation_, not
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during updating or any other lifecycle. They are meant as a means to perform
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bootstrapping of a system.
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If a creation-time provisioner fails, the resource is marked as **tainted**.
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A tainted resource will be planned for destruction and recreation upon the
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next `terraform apply`. Terraform does this because a failed provisioner
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can leave a resource in a semi-configured state. Because Terraform cannot
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reason about what the provisioner does, the only way to ensure proper creation
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of a resource is to recreate it. This is tainting.
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You can change this behavior by setting the `on_failure` attribute,
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which is covered in detail below.
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## Destroy-Time Provisioners
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If `when = "destroy"` is specified, the provisioner will run when the
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resource it is defined within is _destroyed_.
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Destroy provisioners are run before the resource is destroyed. If they
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fail, Terraform will error and rerun the provisioners again on the next
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`terraform apply`. Due to this behavior, care should be taken for destroy
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provisioners to be safe to run multiple times.
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Destroy-time provisioners can only run if they remain in the configuration
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at the time a resource is destroyed. If a resource block with a destroy-time
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provisioner is removed entirely from the configuration, its provisioner
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configurations are removed along with it and thus the destroy provisioner
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won't run. To work around this, a multi-step process can be used to safely
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remove a resource with a destroy-time provisioner:
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* Update the resource configuration to include `count = 0`.
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* Apply the configuration to destroy any existing instances of the resource, including running the destroy provisioner.
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* Remove the resource block entirely from configuration, along with its `provisioner` blocks.
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* Apply again, at which point no further action should be taken since the resources were already destroyed.
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This limitation may be addressed in future versions of Terraform. For now,
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destroy-time provisioners must be used sparingly and with care.
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## Multiple Provisioners
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Multiple provisioners can be specified within a resource. Multiple provisioners
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are executed in the order they're defined in the configuration file.
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You may also mix and match creation and destruction provisioners. Only
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the provisioners that are valid for a given operation will be run. Those
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valid provisioners will be run in the order they're defined in the configuration
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file.
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Example of multiple provisioners:
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```hcl
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resource "aws_instance" "web" {
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# ...
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provisioner "local-exec" {
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command = "echo first"
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}
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provisioner "local-exec" {
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command = "echo second"
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}
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}
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```
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## Failure Behavior
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By default, provisioners that fail will also cause the Terraform apply
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itself to error. The `on_failure` setting can be used to change this. The
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allowed values are:
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- `"continue"` - Ignore the error and continue with creation or destruction.
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- `"fail"` - Error (the default behavior). If this is a creation provisioner,
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taint the resource.
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Example:
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```hcl
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resource "aws_instance" "web" {
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# ...
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provisioner "local-exec" {
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command = "echo ${self.private_ip_address} > file.txt"
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on_failure = "continue"
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}
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}
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```
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