I have a docker container for MineOS installed to make it easier for my kids to play Minecraft. I setup a few servers for them to play on together but recently the servers all disappeared! It turns out that MineOS expects certain user/group permissions on all the files that MineOS has. I found a thread on a the docker forum that was an exact duplicate of my issue. I simply had to log into the command line on my unRAID server and type the following command:
chown -R 1000:1000 /mnt/user/appdata/minecraftos
After that, I restarted my docker container and all the servers were present and working again!