How to install additional packages in Docker container?

I'm sure this is a basic task, but I'm brand new to docker and having trouble figuring out how to do this within the OMV framework.

I'm running handbrake in a container and also need mkvtoolnix installed for some automation. This seems to be the best/simplest example that I've found for that:

How to install packages from Docker compose?

Hi there I am new to Docker. I have an docker-compose.yml which looks like this: version: "3" services: lmm-website: image:…

stackoverflow.com

It uses compose to setup the container and then Dockerfile to install the package I need. I'm able to run the container successfully, but the RUN command in Dockerfile doesn't seem to be getting executed. If I run the same as root in the running container, mkvtoolnix installs just fine.

Here's the container I'm running, for reference:

GitHub - jlesage/docker-handbrake: Docker container for HandBrake

Docker container for HandBrake. Contribute to jlesage/docker-handbrake development by creating an account on GitHub.

github.com

My compose file:

---
version: '3'
services:
  handbrake:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: handbrake
    environment:
      - USER_ID=1000
      - GROUP_ID=1000
      - TZ=${TZ}
      - WEB_LISTENING_PORT=-1
      - VNC_LISTENING_PORT=-1
      - HANDBRAKE_GUI=0
      - INSTALL_PACKAGES=mkvtoolnix
    volumes:
      - CHANGE_TO_COMPOSE_DATA_PATH/handbrake:/config

And my Dockerfile:

FROM jlesage/handbrake:v1.25.1

RUN apk update && apk add --no-cache ${INSTALL_PACKAGES}

I've tried specifying mkvtoolnix instead of through ${INSTALL_PACKAGES} and tried splitting that into multiple RUN statements, but nothing seems to have any effect. I don't get any error message when bringing the container up, and so far haven't been able to find any logs that give a hint on what's failing.

Any suggestions? I feel like I must be missing something really simple.

Thanks for the reply. I actually had tried creating the Dockerfile through the UI, but got the error "Name is in use by a compose file". So I thought I could only build a package using a compose file OR a dockerfile in the OMV UI. I then created the Dockerfile manually in the same directory where OMV created the compose YML file, but obviously that's not working.

Do you mind explaining a bit more how to add this to the Dockerfile tab without getting that name collision error?

Thanks, I got it working. Took me a minute to realize I needed to build the Dockerfile first, then bring up the compose file.