Dosbox

Introduction

This project is Dosbox in an Alpine Linux container, complete with sound support. It was largely inspired by https://github.com/h6w/dosbox-docker and includes a handful of improvements over that project:

• Multi-Stage Build (retain only what is necessary in final image)
• Use Alpine 3 (rather than Edge)
• Use native alsa packages, instead of building them
• Updated version of dosbox (which is obtained directly through SourceForge)
• After build, run as non-root user
• Provide canned dosbox.conf, to mount C and A drives (see below)

Running

In order to use, you'll need to provide X11 and Pulse audio support to the container.

Linux

Audio for Linux is currently untested; I'm not sure if the asound.conf supplied to the container will negate the ability to use /dev/snd.

$ docker run \
    -e DISPLAY=unix$DISPLAY \
    -v /tmp/.X11-unix:/tmp/.X11-unix \
    --device /dev/snd
    classiccontainers/dosbox

Docker for Windows

After installing Docker for Windows,

1. Install X11 Server, such as VcXsrv.
   • Make sure to turn Access Control Off.
2. Install and configure Windows port of Pulse Audio
   • In config.pa, set auth-ip-acl to the Docker bridge network (or full private subnet 172.16.0.0/12); see Pulse Audio Docs for examples.
3. Enable X11 and Pulse Audio through Windows firewall
   • I enabled them for Public and Private networks and set the Remote IP addresses to 172.16.0.0/12
   • The need for this step might depend on whether you use the WSL2 backend for Docker. Currently, Windows considers the WSL2 network interface "Public", so you'll need to allow both programs on public networks and then you'll probably want to lock it down to the Private 172 CIDR for security
   • Pulse Audio has firewall rules for both TCP and UDP; make sure to update both
4. Run the docker container, exporting appropriate variables

   $ docker run \
       -e DISPLAY=host.docker.internal:0 \
       -e PULSE_SERVER=host.docker.internal \
       classiccontainers/dosbox

Saving Games

At startup, DOSBox is configured to mount the A drive to /var/games/dosbox. If you would like to retain game data between container runs, simply mount a local directory to /var/games/dosbox inside the container.

$ docker run \
    -v /home/user1/savedata:/var/games/dosbox \
    classiccontainers/dosbox

Anything you or the game saves to the A drive should then be available on your local machine, and you should be able to load data from the same location on future runs of the container.

I was originally going to use the D drive for the save mount, but I imagine some things out there expect the D drive to be a CD-ROM, and people probably more commonly used the floppy drive at A for transferring saves (and other random stuff) anyway. Hopefully your downstream game/whatever won't barf when it sees a large drive or files on the A drive.

Configuring DOSBox & Extending

This image comes with a canned dosbox.conf which is loaded via the ENTRYPOINT when the container runs; included in the file are autoexec commands to mount the C drive to /home/dosbox and the A drive to /var/games/dosbox (as above).

Since the A and C drives are already in use, you'll need to put elsewhere any image mounts (for floppy or CD-ROM images) you need. See documentation on MOUNT

DOSBox will automatically load a ~/.dosbox/dosbox-{version}.conf file or a ./dosbox.conf file if found. In an attempt to be future-proof about DOSBox version, this image uses ./dosbox.conf, but explicitly loads it with the -conf parameter.

It's not well documented, but DOSBox supports multiple -conf directives, which is why this image explicitly loads ./dosbox.conf. For regular settings, the one found in the last conf file wins, and autoexec directives are merged. This means that you should be able to construct a downstream image, ADD or COPY your own conf file, and use CMD to add additional -conf filename directives are required.

NOTE Remember to chown (or chmod) the file so that the dosbox user can read it!

Example dosbox conf:

[autoexec]
c:
mygame.exe

Example Dockerfile:

FROM classiccontainers/dosbox

# fetch game zip
ADD --chown=dosbox:dosbox https://oldgame.net/oldgame.zip oldgame.zip

RUN unzip mygame.zip

COPY --chown=dosbox:dosbox dosbox_oldgame.conf dosbox_oldgame.conf

CMD ["-conf", "dosbox_oldgame.conf"]

Disclaimer

This project is intended for educational purposes only.