»The post-processor block

The post-processor block defines how a post-processor is configured.

# builds.pkr.hcl
build {
  # ... build image
  post-processor "checksum" { # checksum image
    checksum_types = [ "md5", "sha512" ] # checksum the artifact
    keep_input_artifact = true           # keep the artifact
  }

  post-processor "amazon-import" { # upload image to amazon
  }
}

Each post-processor runs after each defined build. A post-processor takes the Artifact from a build. Post-processors are optional, and they can be used to upload artifacts, re-package, or more. The list of available post-processors can be found in the post-processors section.

A post-processor can also take the Artifact from another post-processor when it is defined in a post-processors block list, that is a list of chained post processors.

»Keep an input artifact

To prevent an input artifact from being deleted, you can set the keep_input_artifact field to true to make Packer keep both artifacts. For example if we want to checksum an artifact and keep the artifact:

# builds.pkr.hcl
build {
  # ...
  post-processor "checksum" {
    checksum_types = [ "md5", "sha512" ]
    keep_input_artifact = true
  }
}

»Run on Specific Builds

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

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

# builds.pkr.hcl
build {
  # ...
  post-processor "checksum" {
    checksum_types = [ "md5", "sha512" ]
    keep_input_artifact = true
    only = ["source.amazon-ebs.example"]
  }
}

The values within only or except are source names, not builder types.

»Build Contextual Variables

Packer allows to access connection information and basic instance state information from a post-processor. These information are stored in the build variable. Check out the Contextual Variables documentation to learn more about and see some examples of how to use them.

»Related

  • The post-processors block allows to define one or more chain of post-processors that will take the output from the build and provision steps.