Debian Jessie with berkshelf-api 2.1.1. Base image: ruby:2.2.3-slim. Tested with Chef Server 12 docker image: 3ofcoins/docker-chef-server.

Assuming that:

• your Chef Server is already running and is accessible by chef.example.com
• there is Chef Server user: berkshelf (probably client is also ok, but never both, you'll most probably get Permission denied when authorizing as berkshelf)

Run this docker image e.g. like this:

$ docker run -dti --name berks -v ${PWD}/test/berkshelf.pem:/home/berkshelf/.chef/berkshelf.pem -e CHEF_SERVER_ENDPOINT="https://chef.example.com:443" -e BERKS_BUILD_INTERVAL=15 -e CHEF_ORGANIZATION="/organizations/testorg" --link chef_server:chef.example.com -p 26200:26200  xmik/berkshelf-api-docker:0.0.4

where:

• you have to mount pem file for Chef Server user: berkshelf
• CHEF_SERVER_ENDPOINT is your Chef Server url reachable from chef workstations. Default is "https://chef.example.com:443". It should be full Chef Server protocol and domain name and port.
• CHEF_CLIENT_NAME is the Chef Server user or client name, default is "berkshelf"
• BERKS_BUILD_INTERVAL sets build_interval - the number of seconds before it refreshes from the endpoints (see berkshelf/berkshelf-api), default here is 5, just as in berkshelf-api. berkshelf-api, if correctly configured, sends 9 messages per build_interval.
• CHEF_ORGANIZATION is obligatory if you use Chef Server 12. Default is empty, so that it works for Chef Server 11. Example value is: "/organizations/testorg" and it must start with slash.
• the link is necessary only if CHEF_SERVER_ENDPOINT is not reachable for berks container, so e.g. when testing.

When berks container is already running and you want to change some configuration, editing /home/berkshelf/.berkshelf/api-server/config.json file will have no effect, because it is generated. Edit then this file: /usr/bin/run_berks_api.sh and restart the container. To login into the container:

$ docker exec -ti berks /bin/bash

To confirm that you have connected from chef workstation to berks-api server, search for some cookbook in your Chef Server, e.g. apt:

$ berks search apt --source http://[container_ip]:26200
apt (2.6.1)

Build an image using the tag from script/version.txt. Use rake task:

$ rake build

Size of berkshelf-api-docker:0.0.4 is 500 MB.

There is a directory: test, which contains files needed to test the deployment of Chef Server 12 (using 3ofcoins/docker-chef-server docker image) and this berkshelf-api docker image. The script run.sh contains all the steps needed. Part of it can be ran automatically. There is also a result of running knife backup export on Chef Server 11 to test running knife backup restore.