Add an Amazon EC2 Instance to the Stack

In this task, your objective is to add an Amazon EC2 instance to the template, then update the stack with the revised template.

Whereas the bucket definition was rather simple (just two to four lines), defining an Amazon EC2 instance is more complex because it needs to use associated resources, such as an AMI, security group and subnet.

For this exercise we will assume you now know how to edit your CloudFormation template and update your CloudFormation stack with the updated template.

5.1 Get the latest AMI to use for your EC2 instance

In the Parameters section of your template, look at the LatestAmiId parameter.

LatestAmiId:
  Description: Gets the latest AMI from Systems Manager Parameter store
  Type: 'AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>'
  Default: '/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2'

This is a special parameter. This parameter uses the AWS Systems Manager Parameter Store to retrieve the latest AMI (specified in the Default parameter, which in this case is Amazon Linux 2) for the stack’s region. This makes it easy to deploy stacks in different regions without having to manually specify an AMI ID for every region.

  • Go to the AWS CloudFormation console
    • Click on Stacks
    • Click on the CloudFormationLab stack
    • Click on the Parameters tab
  • Look at the Value and Resolved value for LatestAmiId
    • You see here how it resolves to an AMI ID

For more details of this method, see: AWS Compute Blog: Query for the latest Amazon Linux AMI IDs using AWS Systems Manager Parameter Store

5.2 Add the EC2 instance resource to your CloudFormation template and deploy it

  1. Edit the CloudFormation Template, adding a new resource for an EC2 instance

    Use this documentation page for assistance: AWS::EC2::Instance

    • Use the YAML format
    • For Logical ID (the line above Type) use MyEC2Instance

    You only need to specify these five properties:

    • ImageId: References LatestAmiId, which is the parameter discussed previously

    • InstanceType: References InstanceType, another parameter

    • SecurityGroupIds: References PublicSecurityGroup, which is defined elsewhere in the template

    • SubnetId: References PublicSubnet1, which is defined elsewhere in the template

    • Tags: Use this YAML block:

        Tags:
    - Key: Name
      Value: Simple Server

    Remember

    • When referencing other resources in the same template, use !Ref. See the BucketName example you already implemented

    • When referencing SecurityGroupIds, CloudFormation is expecting a list of security groups. You therefore need to list the security group like this:

        SecurityGroupIds:
    - !Ref PublicSecurityGroup

    • Not sure what to do???

      • To download a sample solution, right-click and download this link: simple_stack_plus_s3_ec2.yaml
      • Or click below to see exactly what to add to your CloudFormation template.
    Click here to see YAML for adding your EC2 instance:

  2. Once you have edited the template, update the stack deployment with your revised template file.

    • On the Parameters screen of the CloudFormation update switch EC2SecurityEnabledParam to true

      Important
      Change EC2SecurityEnabledParam to true
      This will tell the template to create resources your EC2 instance will need such as the Security Group and IAM Role

    • This deployment of the CloudFormation stack will take about three minutes

    • After the stack status is UPDATE_COMPLETE, the instance will be displayed in the Resources tab.

  3. Go to the EC2 console to see the Simple Server that was created. Explore the properties of this EC2 instance.

The final deployment is now represented by this architecture diagram:

SimpleVpcEverything

5.3 Add a web server to the EC2 instance

In this task you will update your CloudFormation template to modify the deployed EC2 instance so that it runs a simple web server

  1. Modify the EC2 resource in the template

    • Delete the following properties from the EC2 resource

      • SecurityGroupIds
      • SubnetId

    • Add the following properties using the YAML below

      • NetworkInterfaces: adds an external IP address (and DNS name) for the EC2 instance
      • UserData: a simple bash script to install and run an Apache web server. This runs on EC2 instance creation only.

    • Visually the diff for this looks like:

      AddServerDiff

    • The final EC2 instance resource should look like this:

          MyEC2Instance:
      Type: AWS::EC2::Instance
      Properties:
        ImageId: !Ref LatestAmiId
        InstanceType: !Ref InstanceType
        Tags:
          - Key: Name
            Value: Simple Server
        NetworkInterfaces:
          - AssociatePublicIpAddress: "true"
            DeviceIndex: "0"
            GroupSet:
              - Ref: PublicSecurityGroup
            SubnetId:
              Ref: PublicSubnet1
        UserData:
          Fn::Base64:
            !Sub |
              #!/bin/bash -xe
              yum -y update
              sudo yum install -y httpd
              sudo systemctl start httpd
              sudo echo '<h1>Hello from ${AWS::Region}</h1>' > /var/www/html/index.html

  2. Add an output value so you can easily find the public DNS of the EC2 instance

    • Insert the following YAML under the Outputs section of your CloudFormation template

        PublicServerDNS:
    Value: !GetAtt MyEC2Instance.PublicDnsName

    • Use the other entry under Outputs to ensure your new entry has the right indentation

    • The !GetAtt function can return various attributes of the resource. In this case the public DNS name of the EC2 instance.

    • NOTE: if you used a Logical ID other than MyEC2Instance when you added your EC2 resource, then you should use that name here

    • To download a sample solution, right-click and download this link: simple_stack_plus_s3_ec2_server.yaml

  3. Update the CloudFormation stack using the modified template

  4. After deployment is complete and stack status is UPDATE_COMPLETE, click on the Outputs tab for the CloudFormation stack

    • Click on the public DNS name

ClickPublicDns

You should see the Apache HTTP server Test Page, indicating your EC2 instance is running the web server and is accessible from the Internet.