We found quick instructions for creating a Docker container for the OpenHAB 2.3.0 snapshot. These instructions evidently presuppose some basic knowledge of building Docker containers, so I thought I’d write the “I don’t know what I am doing” version of the instructions. Beyond the obvious download & install Docker, then make sure it’s functional (service starts).

The linked Dockerfile is not the only thing you need. Go up a level — you need both the Dockerfile and entrypoint.sh files. Create a directory somewhere and grab these two files. Then build the container using

docker build -t oh2imagename .

I used a short, alpha-numeric only name for my image. When I used slashes as in the example, the container would not start. Then make the folders you want to map into OpenHAB2:

mkdir /some/path/to/openhab/addons
mkdir /some/path/to/openhab/conf
mkdir /some/path/to/openhab/userdata

The instructions conflate local users/groups with in-container users/groups. You do not need to create a local user. You do need to indicate the uidNumber and gidNumber for the openhab user and group. Even if you do create the local user and group, then change the /some/path/to/openhab permissions to provide full access to the user … you may well not be able to access the files. That is SELinux, not a file permission issue. The quick/dirty solution is to start the container with the privileged flag:

--privileged=true

Alternately, consult the Universal Archive of All IT Knowledge and figure out how to allow the docker service to write files where you want them. And how to access USB devices if you are trying to use something like a ZWave dongle. We went with the privileged route 🙂 The –name option is just the container name. The –net uses the host network for container communications instead of the bridge network. Saves mapping ports, although you could easily use the bridge network and map out the handful of OpenHab specific ports. The -d runs the container in detached mode. The -e sets some environment flags (used by the user/group creation script that runs upon container startup). The –tty (or -t) attaches a console. Not really used here.

docker run --privileged --name oh2containername --net=host --tty -d -e USER_ID=5555 \
 -e GROUP_ID=5555 oh2imagename

Ideally, your OpenHAB2 instance will be running. Use “docker ps” to list out the running containers. If you don’t see a container with the name supplied above … then something went wrong. You can use “docker history oh2containername” to view a quick history, but “docker logs oh2containername” will probably provide more useful information. We encountered file permission issues (as noted above, due to SELinux) which prevented the initial container setup from running. Once that was sorted, the container showed up in the running container list.

You’re ready to use it — you can access the web console using your computer’s IP address (assuming you set this container up in the host network and not the bridge — if you used the bridge, you can use “docker inspect oh2containername” and look for IPAddress under NetworkSettings) on the default port. You can ssh into the Karaf console with the default user/password on the default port. Or you can shell into the container.

docker exec -it oh2containername /bin/bash

This is a bash shell running on the OH2 container — you’ll find a lot of ‘stuff’ hasn’t been installed, and your normal command aliases won’t be present. But it’s a shell on the server and can be used to start/stop OH2.