single-instance-with-parameters.template.json

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Description": "Launch single EC2 Instance",
  "Resources": {
    "MyInstance": {
      "Type": "AWS::EC2::Instance",
      "Properties": {
        "AvailabilityZone": "us-east-1a",
        "InstanceType": {"Ref": "InstanceType"},
        "ImageId": "ami-0baf67670ca0f3719",
        "SecurityGroups": [
          {
            "Ref": "MySG"
          }
        ],
        "KeyName": {"Ref": "KeyName"},
        "Tags": [
          {
            "Key": "Name",
            "Value": "Test Instance"
          }
        ]
      }
    },
    "MySG": {
      "Type": "AWS::EC2::SecurityGroup",
      "Properties": {
        "GroupDescription": "Enable HTTP & SSH access",
        "SecurityGroupIngress": [
          {
            "IpProtocol": "tcp",
            "FromPort": "22",
            "ToPort": "22",
            "CidrIp": "0.0.0.0/0"
          },
          {
            "IpProtocol": "tcp",
            "FromPort": "80",
            "ToPort": "80",
            "CidrIp": "0.0.0.0/0"
          }
        ]
      }
    }
  },
  "Parameters": {
    "KeyName": {
      "Description": "Existing KeyPair",
      "Type": "AWS::EC2::KeyPair::KeyName",
      "ConstraintDescription": "Must be an existing key pair"
    },
    "InstanceType": {
      "Description": "Instance Type",
      "Type": "String",
      "Default": "t2.micro",
      "AllowedValues": [
        "t1.micro",
        "t2.nano",
        "t2.micro",
        "t2.small",
        "t2.medium",
        "t2.large"
      ],
      "ConstraintDescription": "valid instance type"
    }
  }
}