Packer is a tool for automatically creating VM and container images, configuring them and post-processing them into standard output formats.

We build the CI images via Packer.

You'll need to install Packer, of course.

The Packer configuration is divided into build-specific variables, output-specific templates and a set of shared provisioning scripts. To do a specific build, combine the template for the desired output artifact type with a variable file. To build a new baseline instance the following would be done:

packer build -var-file=vars/cloud-env.json -var-file=vars/centos.json templates/baseline.json

NOTE: vars/cloud-env.json is a gitignored file as it contains private information. There is a vars/cloud-env.json.example file that may be used as a base for creating the one needed.

From a high level, the build process is:

• Boot a specified base image in any defined clouds.
• Run a set of shell scripts, listed in the template's shell provisioner section, to do any configuration required by the builder.
• Execute a shutdown of the running instance in the clouds.
• Execute the cloud specific method for creating a new image from the shutdown instance
• Perform the cloud specific method for deleting the shutdown instance