» Vagrant Boxes

Packer also has the ability to take the results of a builder (such as an AMI or plain VMware image) and turn it into a Vagrant box.

This is done using post-processors. These take an artifact created by a previous builder or post-processor and transforms it into a new one. In the case of the Vagrant post-processor, it takes an artifact from a builder and transforms it into a Vagrant box file.

Post-processors are a generally very useful concept. While the example on this getting-started page will be creating Vagrant images, post-processors have many interesting use cases. For example, you can write a post-processor to compress artifacts, upload them, test them, etc.

Let's modify our template to use the Vagrant post-processor to turn our AWS AMI into a Vagrant box usable with the vagrant-aws plugin. If you followed along in the previous page and setup DigitalOcean, Packer can't currently make Vagrant boxes for DigitalOcean, but will be able to soon.

» Enabling the Post-Processor

Post-processors are added in the post-processors section of a template, which we haven't created yet. Modify your example.json template and add the section. Your template should look like the following:

  "builders": ["..."],
  "provisioners": ["..."],
  "post-processors": ["vagrant"]

In this case, we're enabling a single post-processor named "vagrant". This post-processor is built-in to Packer and will create Vagrant boxes. You can always create new post-processors, however. The details on configuring post-processors is covered in the post-processors documentation.

Validate the configuration using packer validate.

» Using the Post-Processor

Just run a normal packer build and it will now use the post-processor. Since Packer can't currently make a Vagrant box for DigitalOcean anyway, I recommend passing the -only=amazon-ebs flag to packer build so it only builds the AMI. The command should look like the following:

$ packer build -only=amazon-ebs example.json

As you watch the output, you'll notice at the end in the artifact listing that a Vagrant box was made (by default at packer_aws.box in the current directory). Success!

But where did the Amazon EBS builder artifact go? When using post-processors, Vagrant removes intermediary artifacts since they're usually not wanted. Only the final artifact is preserved. This behavior can be changed, of course. Changing this behavior is covered in the documentation.

Typically when removing intermediary artifacts, the actual underlying files or resources of the artifact are also removed. For example, when building a VMware image, if you turn it into a Vagrant box, the files of the VMware image will be deleted since they were compressed into the Vagrant box. With creating AWS images, however, the AMI is kept around, since Vagrant needs it to function.