Creating a Launch Template

STOP Please note: This workshop version is now deprecated, and an updated version has been moved to AWS Workshop Studio. This workshop remains here for reference to those who have used this workshop before for reference only. Link to updated workshop is here: Launching EC2 Spot Instances.

As a prerequisite step before creating EC2 Auto Scaling groups or EC2 Fleet, you create a launch template. Launch templates enable you to define launch parameters so that you do not have to specify them every time you launch an instance. It includes the ID of the Amazon Machine Image (AMI), the instance type, a key pair, security groups, and other parameters used to launch EC2 instances.

Note: During this workshop, you use your account’s default VPC to create the instances. If your account does not have a default VPC you can create or nominate one following this link

Creating a launch template

  1. Create launch-template-data.json configuration file in CloudShell by running below commands. When you examine the configuration, you notice that ImageId parameter has a placeholder value %ami-id%, and UserData contains a base64 encoded Webserver installation steps. Once you have created the launch template, you can describe it and decode the user-data to view the content.
cat << EOF > launch-template-data.json
{
  "ImageId": "%ami-id%",
  "TagSpecifications": [
    {
      "ResourceType": "instance",
      "Tags": [
        {
          "Key": "Name",
          "Value": "mySpotWorkshop"
        }
      ]
    }
  ],
  "UserData": "I2Nsb3VkLWNvbmZpZwpyZXBvX3VwZGF0ZTogdHJ1ZQpyZXBvX3VwZ3JhZGU6IGFsbAoKcGFja2FnZXM6CiAgLSBodHRwZAogIC0gY3VybAoKcnVuY21kOgogIC0gWyBzaCwgLWMsICJhbWF6b24tbGludXgtZXh0cmFzIGluc3RhbGwgLXkgZXBlbCIgXQogIC0gWyBzaCwgLWMsICJ5dW0gLXkgaW5zdGFsbCBzdHJlc3MtbmciIF0KICAtIFsgc2gsIC1jLCAiZWNobyBoZWxsbyB3b3JsZC4gTXkgaW5zdGFuY2UtaWQgaXMgJChjdXJsIC1zIGh0dHA6Ly8xNjkuMjU0LjE2OS4yNTQvbGF0ZXN0L21ldGEtZGF0YS9pbnN0YW5jZS1pZCkuIE15IGluc3RhbmNlLXR5cGUgaXMgJChjdXJsIC1zIGh0dHA6Ly8xNjkuMjU0LjE2OS4yNTQvbGF0ZXN0L21ldGEtZGF0YS9pbnN0YW5jZS10eXBlKS4gPiAvdmFyL3d3dy9odG1sL2luZGV4Lmh0bWwiIF0KICAtIFsgc2gsIC1jLCAic3lzdGVtY3RsIGVuYWJsZSBodHRwZCIgXQogIC0gWyBzaCwgLWMsICJzeXN0ZW1jdGwgc3RhcnQgaHR0cGQiIF0KCgo="
}
EOF
  1. The variable %ami-id% should be replaced with the latest Amazon Linux 2 AMI. You pull the latest Amazon Linux 2 AMI ID and update the AMI Id in your configuration file by running following commands.
# First, this command looks up the latest Amazon Linux 2 AMI
export ami_id=$(aws ec2 describe-images --owners amazon --filters "Name=name,Values=amzn2-ami-kernel*gp2" "Name=virtualization-type,Values=hvm" "Name=root-device-type,Values=ebs" --query "sort_by(Images, &CreationDate)[-1].ImageId" --output text)

sed -i.bak -e "s#%instanceProfile%#$instanceProfile#g" -e "s#%ami-id%#$ami_id#g" launch-template-data.json
  1. Create the launch template using the config you just updated. You can check other parameters supported by launch template here.
aws ec2 create-launch-template --launch-template-name TemplateForWebServer --launch-template-data file://launch-template-data.json

Example return

{
    "LaunchTemplate": {
        "CreateTime": "2019-02-14T05:53:07.000Z",
        "LaunchTemplateName": "TemplateForWebServer",
        "DefaultVersionNumber": 1,
        "CreatedBy": "arn:aws:iam::123456789012:user/xxxxxxxx",
        "LatestVersionNumber": 1,
        "LaunchTemplateId": "lt-00ac79500cbd56d11"
    }
}
  1. Take a look at the user-data script configured on the launch template to understand what is installed on the instances while being bootstrapped.
aws ec2 describe-launch-template-versions  --launch-template-name TemplateForWebServer --output json | jq -r '.LaunchTemplateVersions[].LaunchTemplateData.UserData' | base64 --decode
  1. As the last step of this section, you are going to perform an additional API call to retrieve the identifier of the launch template that was just created and store it in an environment variable. You use this launch template ID when creating Auto Scaling groups, EC2 Fleets, and Spot Fleets.
export LAUNCH_TEMPLATE_ID=$(aws ec2 describe-launch-templates --filters Name=launch-template-name,Values=TemplateForWebServer | jq -r '.LaunchTemplates[0].LaunchTemplateId')

Well done! You have created a launch template and stored into environment variables all the details that you need to refer to it in the next steps.

Site Info