I would like to share the new address for the Ubuntu version used on this project: [http://old-releases.ubuntu.com/releases/14.04.4/ubuntu-14.04.4-server-amd64.iso](url) Write it on application-server.json file as "iso_url" value. Hope it helps anyone who has my same error with the checksum after running the "packer build" command. Hi, Simone