---
description: |
  The provisioner block defines how a provisioner is configured.
page_title: provisioner - build - Blocks
sidebar_title: <tt>provisioner</tt>
---

# The `provisioner` block

`@include 'from-1.5/beta-hcl2-note.mdx'`

The `provisioner` block defines how a provisioner is configured.

```hcl
# builds.pkr.hcl
build {
  # ...
  provisioner "shell" {
    inline = [
      "echo provisioning all the things",
      "echo the value of 'foo' is '${var.foo}'",
    ]
  }
}
```

Provisioners use builtin and third-party software to install and configure the
machine image after booting. Provisioners prepare the system for use.

The list of available provisioners can be found in the
[provisioners](/docs/provisioners) section.

## Run on Specific Builds

You can use the `only` or `except` configurations to run a provisioner only
with specific builds. These two configurations do what you expect: `only` will
only run the provisioner on the specified builds and `except` will run the
provisioner on anything other than the specified builds.

An example of `only` being used is shown below, but the usage of `except` is
effectively the same:

```hcl
# builds.pkr.hcl

source "amazon-ebs" "first-example" {
  #...
}

source "amazon-ebs" "second-example" {
  #...
}

build {
  source = [
    "source.amazon-ebs.first-example",
    "source.amazon-ebs.second-example",
  ]
  provisioner "shell" {
    # This provisioner only runs for the 'first-example' source.
    only = ["amazon-ebs.first-example"]

    inline = [
      "echo provisioning all the things",
      "echo the value of 'foo' is '${var.foo}'",
    ]
  }
  provisioner "shell" {
    # This runs with all sources.
    inline = [
        "echo Hi World!"
      ]
  }
}
```

The values within `only` or `except` are _build names_, not builder types.

## On Error Provisioner

You can optionally create a single specialized provisioner called an
`error-cleanup-provisioner`. This provisioner will not run unless the normal
provisioning run fails. If the normal provisioning run does fail, this special
error provisioner will run _before the instance is shut down_. This allows you
to make last minute changes and clean up behaviors that Packer may not be able
to clean up on its own.

For examples, users may use this provisioner to make sure that the instance is
properly unsubscribed from any services that it connected to during the build
run.

Toy usage example for the error cleanup script:

```hcl
source "null" "example" {
  communicator = "none"
}

build {
  sources = ["source.null.example"]

  provisioner "shell-local" {
    inline = ["exit 2"]
  }

  error-cleanup-provisioner "shell-local" {
    inline = ["echo 'rubber ducky'> ducky.txt"]
  }
}
```

## Pausing Before Running

With certain provisioners it is sometimes desirable to pause for some period of
time before running it. Specifically, in cases where a provisioner reboots the
machine, you may want to wait for some period of time before starting the next
provisioner.

Every provisioner definition in a Packer template can take a special
configuration `pause_before` that is the amount of time to pause before running
that provisioner. By default, there is no pause. An example is shown below:

```hcl
# builds.pkr.hcl
build {
  # ...
  provisioner "shell" {
      inline = [
        "echo provisioning all the things",
        "echo the value of 'foo' is '${var.foo}'",
      ]
      pause_before = "10s"
  }
}
```

For the above provisioner, Packer will wait 10 seconds before uploading and
executing the shell script.

## Retry on error

With certain provisioners it is sometimes desirable to retry when it fails.
Specifically, in cases where the provisioner depends on external processes that are not done yet.

Every provisioner definition in a Packer template can take a special
configuration `max_retries` that is the maximum number of times a provisioner will retry on error.
By default, there `max_retries` is zero and there is no retry on error. An example is shown below:

```hcl
# builds.pkr.hcl
build {
  # ...
  provisioner "shell" {
      inline = [
        "echo provisioning all the things",
        "echo the value of 'foo' is '${var.foo}'",
      ]
      max_retries = 5
  }
}
```

For the above provisioner, Packer will retry maximum five times until stops failing.
If after five retries the provisioner still fails, then the complete build will fail.

## Timeout

Sometimes a command can take much more time than expected

Every provisioner definition in a Packer template can take a special
configuration `timeout` that is the amount of time to wait before
considering that the provisioner failed. By default, there is no timeout. An
example is shown below:

```hcl
# builds.pkr.hcl
build {
  # ...
  provisioner "shell" {
      inline = [
        "echo provisioning all the things",
        "echo the value of 'foo' is '${var.foo}'",
      ]
      timeout = "5m"
  }
}
```

For the above provisioner, Packer will cancel the script if it takes more than
5 minutes.

Timeout has no effect in debug mode.

## Build Contextual Variables

Packer allows to access connection information and basic instance state information from a provisioner. These information are stored in the `build` variable.
Check out the [Contextual Variables](/docs/templates/hcl_templates/contextual-variables) documentation to learn more about and see some examples of how to use them.
