Every now and then, I get a little nostalgic, and want to play an old computer game that I used to play when I was a kid. I didn’t grow up with consoles like most people my age, rather I had a PC. It not only served as a platform for gaming, but also as a platform for learning things and having fun the process. It was on my mighty 286 that I first started to learn to code, and it was also on that machine where I played many games that I’m still very fond of like the Commander Keen series, Prince of Persia, Where in the World is Carmen San Diego, Wolfenstein 3D, and many others. Nostalgia has largely been the force that has kept these games around too. You can still download many of the shareware versions of these games from sites online over 25 years later and play them in emulators like DosBox.

But I wanted to take my nostalgia to a whole new level: would it be possible to containerize DosBox and expose it in such a way that I could play games in a browser? If nothing else, this would be a trivial, yet fun way to show how to use Kubernetes. In any case, challenge accepted!

My basic theory was this: get DosBox running in such a way that I could connect a VNC client to it and run the games. To do this, there’s a lot of middleware. DosBox works through a window manger, which needs X11, and to broadcast that it needs a VNC Server. So, I started the process of containerizing all these components. Surprisingly, it wasn’t that hard. I used TightVNC Server for the VNC server, the one and only X11, then RatPoison for the desktop/window manger. Once all these were configured, I bolted up NoVNC, an HTML5-based VNC client to TightVNC to expose the games in a browser. It all worked well (maybe too well) dockerfile was surprisingly small.

To use it is pretty straight forward.

DosBox in a Container with VNC Client

  1. Create a folder.
  2. Place a copy of your game in the folder. I am using the shareware version of Commander Keen here.
  3. In that folder, create a file called dockerfile, paste in the following code. 
    FROM ubuntu:18.04
ENV USER=root
ENV PASSWORD=password1
ENV DEBIAN_FRONTEND=noninteractive 
ENV DEBCONF_NONINTERACTIVE_SEEN=true
COPY keen /dos/keen
RUN apt-get update && \
 echo "tzdata tzdata/Areas select America" > ~/tx.txt && \
 echo "tzdata tzdata/Zones/America select New York" >> ~/tx.txt && \
 debconf-set-selections ~/tx.txt && \
 apt-get install -y tightvncserver ratpoison dosbox novnc websockify && \
 mkdir ~/.vnc/ && \
 mkdir ~/.dosbox && \
 echo $PASSWORD | vncpasswd -f > ~/.vnc/passwd && \
 chmod 0600 ~/.vnc/passwd && \
 echo "set border 0" > ~/.ratpoisonrc  && \
 echo "exec dosbox -conf ~/.dosbox/dosbox.conf -fullscreen -c 'MOUNT C: /dos'" >> ~/.ratpoisonrc && \
 export DOSCONF=$(dosbox -printconf) && \
 cp $DOSCONF ~/.dosbox/dosbox.conf && \
 sed -i 's/usescancodes=true/usescancodes=false/' ~/.dosbox/dosbox.conf && \
 openssl req -x509 -nodes -newkey rsa:2048 -keyout ~/novnc.pem -out ~/novnc.pem -days 3650 -subj "/C=US/ST=NY/L=NY/O=NY/OU=NY/CN=NY [email protected]"
PORT 6080
CMD vncserver && websockify -D --web=/usr/share/novnc/ --cert=~/novnc.pem 6080 localhost:5901 && tail -f /dev/null
  4. Replace the COPY keen /dos/keen with your game (ie. COPY wolf3d /dos/wolf3d). 1. You can also change the default password, or override it with a -e parameter when you run the image.
  5. Now, with Docker, build the image. I’m assuming you already have Docker installed and are familiar with it to some extent. CD to the directory in a console and run the command… 
     docker build -t mydosbox .
  6. Run the image. 
     docker run -p 6080:6080 dosbox
  7. Open a browser and point it to http://localhost:6080/vnc.html
  8. You should see a prompt for the password. Type it in, and you should be able to connect to your container with DosBox running. You can now use the command prompt to start your games.

Once your image is built, you can push it to your image repository with docker push, but you’ll need to tag it appropriately.

Use with Kubernetes

Kubernetes is another part of the equation when it comes to container apps. Containers on Kubernetes are deployed into pods, which are then usually a part of a part of a deployment, which will have one or more pods associated with it. Deployments can also be used for creating scalable sets of pods for high availability too on a Kubernetes cluster. If you’re not familiar with Kubernetes, check out this webinar below where I go in depth on the matter.

Deployments and services can be defined declaratively with a YAML file. Below is a Kuberenetes YAML file that defines a deployment and a service for my retro gaming container.

The deployment is simple – it points to a single container image called blaize/keen and then tells Kubernetes what ports to expose for the container. The service defines how the deployment will be exposed on a network. In this case, it’s using a TCP load balancer, where it is exposing port 80 and mapping that to the port exposed by the deployment. The service uses selectors on the label app to match the service with the deployment.

apiVersion: v1
kind: Service
metadata:
  name: keen-service
  labels:
    app: keen-deployment
spec:
  ports:
  - port: 80
    targetPort: 6080
  selector:
    app: keen-deployment
  type: LoadBalancer
---
apiVersion: apps/v1 
kind: Deployment
metadata:
  name: keen-deployment
spec:
  selector:
    matchLabels:
      app: keen-deployment
  replicas: 1
  template:
    metadata:
      labels:
        app: keen-deployment
    spec:
      containers:
      - name: master
        image: blaize/keen
        ports:
        - containerPort: 6080

To connect use this, first create a file called keen.yaml file, configure your instance kubectl to work with your instance of Kubernetes, then run deploy the sample.

kubectl create -f keen.yaml

When this is deployed to Kubernetes, Kubernetes will configure the external network to open on port 80 to listen to incoming requests. When used on Azure Kubernetes Services, AKS will create and map a public IP address (htttp://[your ip address]/vnc.html) for the service. Once connected, you can point your browser to the IP address of your cluster and have fun playing your retro games!