There are several pieces that are used to build this image:
We start with an Alpine base image and add CA certificates in order to reach
the HashiCorp releases server. These are useful to leave in the image so that
the container can access Atlas features as well.
Official HashiCorp builds of some base utilities are then included in the
image by pulling a release of docker-base. This includes dumb-init and gosu.
See https://github.com/hashicorp/docker-base for more details.
Finally a specific Consul build is fetched and the rest of the Consul-specific
configuration happens according to the Dockerfile.