Packer
post-processors block
This topic provides reference information about the post-processors block.
Description
Add a post-processors block to your build block to include a list of post-processor configurations. Packer runs the post-processors for an artifact after 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
    }
  }
}
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-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.