Config有无法识别的密钥：来源

Question

我正在尝试将其转换为https://coreos.com/ignition/docs/latest/migrating-configs.html之后的点火文件：

storage:
  files:
  - filesystem: root
    path: "/etc/hosts"
    append: true
    contents:
      source: data:,
    mode: 420
  filesystems:
  - mount:
      device: "/dev/xvdb"
      format: ext4
    name: ephemeral1

但是出现此错误

ct --in-file cloud-config.yml --pretty --out-file RUBY-STACK1-STAGE.ign
warning at line 13, column 7
Config has unrecognized key: source