• Love Packer?
  • Frustrated by the lack of support for YAML?
  • Even though the process of converting YAML to JSON is, well, simple?

Well, now there’s yacker!

yacker is an open-source Python YAML interpreter for HashiCorp’s Packer. It wraps Packer in a converting wrapper that allows you to drive it with YAML files.

Now you can craft your Packer files in YAML rather than JSON. Then, instead of running packer on JSON files, you run yacker on your YAML files:

yacker build template.yml

All yacker does is translate YAML to JSON on the fly (a super-trivial act in Python), calling on Packer to do the rest.

Now you can benefit from the more pleasant environment that YAML provides and still use a pretty cool tool.

yacker: -

  • searches the command-line for .yml (or .yaml) files (specifically looking for the template and any -var-file references)
  • converts the files (if found) to JSON files
  • reconstructs the command line (using the remaining options)
  • passes control to packer
  • removes the JSON files it created
  • passes control (and Packer’s exit code) back to you

Packer’s output and any errors are simply presented to you as if you’d run Packer using JSON.

Variable Files

yacker also translates any YAML-based variable files you may have. If you name a YAML file in any -var-file argument yacker will temporarily convert that file for you before passing it to Packer and then removing it:

yacker build -var-file=v1.yml -var-file=v2.yml template.yml


yacker expects to find packer on the system PATH.

If you don’t have Packer on the system path, or want to use a different Packer, you can provide a path to it by using the YACKER_PACKER_PATH environment variable:

YACKER_PACKER_PATH=~/bin yacker version


yacker version
yacker build template.yml