如何在Cloudformation中将资源ID导入UserData

echo ${!Ref EFSFileSystem} 这样地:

  EFSFileSystem:
    Type: AWS::EFS::FileSystem
    Properties:
        ...


  InstanceLc:
    Type: AWS::AutoScaling::LaunchConfiguration
    Properties:
      ...
      UserData:
        Fn::Base64: !Sub |
          #!/bin/bash -xe
          exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
          aws s3 cp s3://aws-cloudinit/install.sh - | bash
          echo ${!Ref EFSFileSystem}

但在日志中我发现这给了我一个错误:

/var/lib/cloud/instance/scripts/part-001: line 4: ${Ref EFSFileSystem}: bad substitution

我找到了一些例子。 https://github.com/awslabs/aws-cloudformation-templates/blob/master/community/services/EFS/efs_with_automount_to_ec2.json

在UserData中导入efs文件系统id的正确语法是什么?