Thanks much Max! This is very cool information. I had erroneously assumed I needed to run a separate docker-compose container, when in reality, the docker package on my Synology understands the docker-compose command all by itself. I put the .yml file into the volume1/docker folder where the MC26 and MC27 folders reside as well. All I needed to do then was ssh in, cd to the docker directory and execute the docker-compose pull command. However, the docker-compose down command didn't work as it didn't remove the old container, but didn't throw an error either. So when I ran docker-compose up -d, I got an error:
ERROR: for jrivermc27 Cannot create container for service jrivermc27: Conflict. The container name "/jrivermc27" is already in use by container "very long HEX number, I think". You have to remove (or rename) that container to be able to reuse that name.
Because I was a bit paranoid and didn't want to loose the container that works, I changed the name of the container and ran the up -d again and, voilā, there is the updated MC27.0.12 running in docker. I love it.
Thank you again so much!
cheers,
Hans