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The source block

Note: This page is about HCL2 Packer templates. HCL2 templates were first introduced as a beta feature into Packer version 1.5. As of v1.7, HCL2 support is no longer in beta, and is the preferred way to write Packer configuration. For the old-style stable configuration language see template docs. As of v1.6.2, you can convert your legacy JSON template into an HCL2 config file using the hcl2_upgrade command.

The top-level source block defines reusable builder configuration blocks:

# sources.pkr.hcl
source "happycloud" "foo" {
    // ...
}

The first label — happycloud here — is the builder type. The second label is the unique name or identifier you want to give to the source. There can be only one source.happycloud.foo top-level source block; but it can be used more than once. Builders are usually found in plugins, except for the file and the null builders that will remain in Packer core.

You can start builders by referring to those source blocks from a build block :

build {
  sources = [
    # Here Packer will use a default ami_name when saving the image.
    "source.happycloud.example",
    "source.happycloud.foo",
  ]
}

The build-level source block allows to set specific source fields. Each field must be defined only once and it is currently not allowed to override a value.

build {
  source "source.happycloud.example" {
    # Here Packer will use the provided image_name instead of defaulting it.
    # Note that fields cannot be overwritten, in other words, you cannot
    # set the 'image_name' field in the top-level source block and here at the
    # same time
    image_name = "build_specific_field"
  }
}

Source Variables

It is possible to access the name and type of your source from provisioners and post-processors:

source "null" "first-example" {
  communicator = "none"
}

build {
  name = "roles"

  source "null.first-example" {
    name = "consul"
  }
  source "null.first-example" {
    name = "nomad"
  }
  source "null.first-example" {
    name = "vault"
  }
  sources = ["null.first-example"]

  provisioner "shell-local" {
    inline = ["echo ${source.name} and ${source.type}"]
  }
}

# This will echo something like:
#
# roles.null.consul: consul and null
# roles.null.nomad: nomad and null
# roles.null.vault: vault and null
# roles.null.first-example: first-example and null

Related

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