How to Run a Command After Building a Docker Container?

If you're using a LinuxServer image, you can leverage their mods to install packages after the container is created. Check out their universal package install mod on GitHub. You can set it up like this:

```yaml
services:
sabnzbd:
image: lscr.io/linuxserver/sabnzbd:latest
container_name: sabnzbd
environment:
- PUID=1003
- PGID=1003
- TZ=America/New_York
- DOCKER_MODS=linuxserver/mods:universal-package-install
- INSTALL_PACKAGES=ffmpeg
volumes:
- /docker/sabnzbd:/config
- /downloads:/downloads
ports:
- 8080:8080
restart: unless-stopped
```

The reason your container keeps restarting is that your command overrides the container's default startup command. When you specify `command: bash -c "apk add --no-cache ffmpeg"`, it only runs this command. Once it finishes, the container exits, which makes Docker restart it (because of the `restart: unless-stopped` policy). You might want to rethink how you handle commands in the Dockerfile or use a separate script that runs after your service starts.

You might consider using a Dockerfile instead of trying to run commands directly in your Compose file. In the Dockerfile, you can include all your necessary build steps, including package installations. This keeps your container behavior consistent and avoids restart issues. Let me know if you need examples!