example.ign

{
  "ignition": {
    "config": {},
    "security": {
      "tls": {}
    },
    "timeouts": {},
    "version": "2.2.0"
  },
  "networkd": {},
  "passwd": {
    "users": [
      {
        "name": "core",
        "sshAuthorizedKeys": [
          "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCt3BebCHqnSsgpLjo4kVvyfY/z2BS8t27r/7du+O2pb4xYkr7n+KFpbOz523vMTpQ+o1jY4u4TgexglyT9nqasWgLOvo1qjD1agHme8LlTPQSk07rXqOB85Uq5p7ig2zoOejF6qXhcc3n1c7+HkxHrgpBENjLVHOBpzPBIAHkAGaZcl07OCqbsG5yxqEmSGiAlh/IiUVOZgdDMaGjCRFy0wk0mQaGD66DmnFc1H5CzcPjsxr0qO65e7lTGsE930KkO1Vc+RHCVwvhdXs+c2NhJ2/3740Kpes9n1/YullaWZUzlCPDXtRuy6JRbFbvy39JUgHWGWzB3d+3f8oJ/N4qZ cardno:000603633110"
        ]
      }
    ]
  },
  "storage": {
    "files": [
      {
        "filesystem": "root",
        "path": "/etc/hello-message",
        "contents": {
          "source": "data:,HELLO_MESSAGE%3D%22hello%20world!%22%0A",
          "verification": {}
        },
        "mode": 356
      }
    ]
  },
  "systemd": {
    "units": [
      {
        "contents": "[Unit]\nDescription=A hello world service\n[Service]\nType=oneshot\nEnvironmentFile=/etc/hello-message\nExecStart=/usr/bin/echo $HELLO_MESSAGE\n[Install]\nWantedBy=multi-user.target\n",
        "enabled": true,
        "name": "hello.service"
      }
    ]
  }
}