CloudFormation模板启动EC2时报SecurityGroups属性需为字符串列表错误如何解决

• AWS::EC2::Instance的SecurityGroups属性要求类型为字符串列表，你当前直接传入单个!Ref MySG返回的是单个字符串，类型不匹配
• 你指定了SubnetId（即VPC场景下启动EC2），SecurityGroups需要传入安全组ID而非安全组名称，你现有参数MySG的类型配置错误

修改两处配置即可：

1. 将MySG参数的Type改为AWS::EC2::SecurityGroup::Id，默认值替换为你实际的安全组ID（AWS安全组ID为小写sg-开头，原大写SG-格式错误）
2. 将SecurityGroups的赋值改为列表形式，用- !Ref MySG包裹即可

修改后完整模板代码：

Parameters:
  KeyName:
    Description: Name of an existing EC2 KeyPair to enable SSH access to the instance
    Type: 'AWS::EC2::KeyPair::KeyName'
    ConstraintDescription: must be the name of an existing EC2 KeyPair.

  MySubnet:
    Description: My subnet from my VPC
    Type: 'AWS::EC2::Subnet::Id'
    Default: subnet-YYYYYYYY
  
  MySG:
    Description: My Security Group from my VPC
    Type: 'AWS::EC2::SecurityGroup::Id'
    Default: sg-YYYYYYYY
   
Resources:
  Ec2Instance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: ami-09e67e426f25ce0d7
      SecurityGroups: 
        - !Ref MySG
      SubnetId: !Ref MySubnet
      KeyName: !Ref KeyName

内容的提问来源于stack exchange，提问作者Delton