Passing User Data to EC2 Instances via CloudFormation

Key Concepts:

• User data scripts are used to automate the initial setup of EC2 instances.
• CloudFormation allows passing user data scripts to EC2 instances within templates.
• The user data script must be encoded in Base64 when passed through CloudFormation.
• Logs of the user data script execution are stored in /var/log/cloud-init-output.log.

Next Steps:

• Explore how to link the success of the user data script to the success of the CloudFormation stack creation.

Example CloudFormation User Data Section:

UserData:
  Fn::Base64: |
    #!/bin/bash
    sudo dnf update -y
    sudo dnf install -y httpd
    sudo systemctl start httpd
    sudo systemctl enable httpd
    echo "Hello World from user data." > /var/www/html/index.html

Important Notes:

• CloudFormation will report stack creation success even if the user data script fails.
• It is important to verify the user data script execution to ensure the EC2 instance is configured correctly.
• The next lecture will cover how to handle potential user data script failures and their impact on CloudFormation.