I am using this docker-compose.yml
version: '3'
services:
jrivermc27:
image: shiomax/jrivermc27
restart: always
container_name: jrivermc27
network_mode: host
environment:
- VNC_PASSWORD=<choose your own>
- USER_ID-1026
- GROUP_ID=101
- DISPLAY_WIDTH=2560
- DISPLAY_HEIGHT=1440
- TZ=America/New_York
volumes:
- /volume1/docker/MC27/config:/config:rw
- /volume1/music:/data/music:rw
- /volume1/docker/MC27/data/Library:/data/Library:rw
It assumes the following:
1) You have a /volume1 on your NAS
2) You have a folder called "docker" on /volume1
3) You have a folder called "MC27" in /volume1/docker
4) You have a folder called "config" in /volume1/docker/MC27
5) Your media files are located in the folder called "music" on /volume1
6) You have a folder called "data" in /volume1/docker/MC27
7) You have a folder called "Library" in /volume1/docker/MC27/data
You need to replace the USER_ID and GROUP_ID with the values correct for your system. Ditto with the DISPLAY_WIDTH and DISPLAY_HEIGHT (mine are for a 27" iMac). Similarly, if you are not located on the East Coast of the US, replace the value with the correct one.
After you start the container, you can access the GUI on <NAS IP-address>:5800. If you have set up a DDNS hostname for your NAS you can also use <NAS-hostname.local>:5800 to get to the GUI.
I also recommend looking into Portainer. It's another Docker container that lets you easily control/maintain/back-up your docker containers. I use it mainly to update my containers when needed and it takes only a minute.
Hope this helps.
EDIT: I want to mention that without Max's help I would not have been able to do this, as I am pretty n00b myself.