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»The post-processors 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 post-processors block allows to define lists of post-processors, that will run from the artifact of each build.

# builds.pkr.hcl
build {
  # ...
  post-processors {
    post-processor "shell-local" { # create an artifice.txt file containing "hello"
      inline = [ "echo hello > artifice.txt" ]
    }
    post-processor "artifice" { # tell packer this is now the new artifact
      files = ["artifice.txt"]
    }
    post-processor "checksum" { # checksum artifice.txt
      checksum_types = [ "md5", "sha512" ] # checksum the artifact
      keep_input_artifact = true           # keep the artifact
    }
  }

}

# builds.pkr.hcl
build {
  # ...
  post-processors {
    post-processor "shell-local" { # create an artifice.txt file containing "hello"
      inline = [ "echo hello > artifice.txt" ]
    }
    post-processor "artifice" { # tell packer this is now the new artifact
      files = ["artifice.txt"]
    }
    post-processor "checksum" { # checksum artifice.txt
      checksum_types = [ "md5", "sha512" ] # checksum the artifact
      keep_input_artifact = true           # keep the artifact
    }
  }

}

The post-processor block allows to define multiple post-processors that will run from the Artifact of each build. Read the post-processor documentation to know how to use a post-processor.

»Difference between a post-processor and a post-processors block

These two templates are doing the same thing:

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

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

  post-processor "googlecompute-import" { # upload image to GCP
  }
}

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

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

  post-processor "googlecompute-import" { # upload image to GCP
  }
}

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

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

  post-processors {
    post-processor "googlecompute-import" { # upload image to GCP
    }
  }
}

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

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

  post-processors {
    post-processor "googlecompute-import" { # upload image to GCP
    }
  }
}

Each of these post-processors will start after each build -- that is, after each provision step has run on each source --. In all cases the source image is going to be deleted.