tes.json

{
	"AWSTemplateFormatVersion": "2010-09-09",

	"Description": "AWS CloudFormation Sample Template vpc_single_instance_in_subnet.template: Sample template showing how to create a VPC and add an EC2 instance with an Elastic IP address and a security group. **WARNING** This template creates an Amazon EC2 instance. You will be billed for the AWS resources used if you create a stack from this template.",

	"Parameters": {

		"InstanceType": {
			"Description": "WebServer EC2 instance type",
			"Type": "String",
			"Default": "m1.medium",
			"ConstraintDescription": "must be a valid EC2 instance type."
		},

		"KeyName": {
			"Description": "Name of an existing EC2 KeyPair to enable SSH access to the instance",
			"Type": "String",
			"Default": "dfad"

		},
		"ImageID": {
			"Description": "Name of an existing EC2 KeyPair to enable SSH access to the instance",
			"Type": "String",
			"Default": "ami-12345"

		},
		"InstanceSecurityGroup": {
			"Description": " The IP address range that can be used to SSH to the EC2 instances",
			"Type": "AWS::EC2::SecurityGroup::Id",
			"Default": "sg-12345"
		},
		"SubnetId": {
			"Description": " The IP address range that can be used to SSH to the EC2 instances",
			"Type": "AWS::EC2::Subnet::Id",
			"Default": "subnet-12345"
		}

	},
"Resources" : {
	"testInstance": {
		"Type": "AWS::EC2::Instance",
		"Properties": {
			"ImageId": {
				"Ref": "ImageID"
			},
			"SecurityGroupIds": [{
				"Ref": "InstanceSecurityGroup"
			}],
			"SubnetId": {
				"Ref": "SubnetId"
			},
			"InstanceType": {
				"Ref": "InstanceType"
			},
			"KeyName": {
				"Ref": "KeyName"
			}
		}
	}
}

}