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3: CloudFormation Helper Scripts

·1 min

What are CF helper scripts?

  • Python scripts to install software and start services on ec2 boxes
  • Called directly from CF template
  • Work with resource metadata defined in template
  • Send signals back to the stack


  • Retrieve and interpret resource metadata
  • Install packages, create files, start services
  • e.g. start web server


  • Signal between wait condition and the stack what’s going on
  • Is the stack ready to continue build/update?
  • Used with both wait conditions and creation policies


  • Continuously running daemon
  • Checks for updates to metadata
  • Executes custom hooks when changes detected
  • Has an arg to make it run once then exit without daemon’ing


  • Retrieve all metadata for a resource, or:
  • Retrieve path to specific key or subtree of resource data
  • Good for troubleshooting