packer build -only=virtualbox-iso -var-file="rethinc.json" ubuntu.json packer build -only=vmware-iso -var-file="rethinc.json" ubuntu.json Upgrade to next Ubuntu Release: rethinc.json: vm_name, iso_checksum, iso_checksum_type, iso_name, iso_url vgrant-rethinc.tpl: config.vm.box